U.S. patent application number 09/837004 was filed with the patent office on 2001-08-16 for method and apparatus for manufacturing a semiconductor device.
This patent application is currently assigned to Kaneka Corporation. Invention is credited to Hayashi, Katsuhiko, Kondo, Masataka, Kuribe, Eiji.
Application Number | 20010014542 09/837004 |
Document ID | / |
Family ID | 27317953 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014542 |
Kind Code |
A1 |
Kondo, Masataka ; et
al. |
August 16, 2001 |
Method and apparatus for manufacturing a semiconductor device
Abstract
A substrate is washed with a washing liquid. Compressed air is
blown to the substrate to remove the washing liquid. A thin film is
formed on the substrate from which the washing liquid has been
removed.
Inventors: |
Kondo, Masataka; (Kita-ku,
JP) ; Hayashi, Katsuhiko; (Kusatsu, JP) ;
Kuribe, Eiji; (Osaka, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Assignee: |
Kaneka Corporation
|
Family ID: |
27317953 |
Appl. No.: |
09/837004 |
Filed: |
April 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09837004 |
Apr 17, 2001 |
|
|
|
09531549 |
Mar 20, 2000 |
|
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Current U.S.
Class: |
438/755 |
Current CPC
Class: |
H01L 31/18 20130101;
H01L 21/67028 20130101 |
Class at
Publication: |
438/755 |
International
Class: |
H01L 021/302 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 1999 |
JP |
11-139820 |
Aug 12, 1999 |
JP |
11-228521 |
Sep 30, 1999 |
JP |
11-280266 |
Claims
What is claimed is:
1. A method of manufacturing a semiconductor device by forming a
thin film on a substrate, comprises the steps of: (a) washing the
substrate with a washing liquid; (b) removing the washing liquid
from the substrate by blowing a compressed air to the substrate
washed; and (c) forming a thin film on the substrate immediately
after the step (b), without performing another step.
2. The method device according to claim 1, wherein the step (a),
the step (a) comprises the steps of (a-i) washing the substrate
with the washing liquid by use of a brush; (a-ii) rinsing the
brush-washed substrate; and (a-iii) washing the rinsed substrate by
using ultrasonic waves.
3. The method according to claim 1, wherein, in the step (b), the
compressed air to be blown to the substrate is heated to a
predetermined temperature.
4. The method according to claim 1, wherein, in the step (b), the
compressed air to be blown to the substrate is ionized.
5. The method according to claim 1, wherein, the step (c) further
comprises a step of heating the substrate to a predetermined
temperature before the thin film is formed on the substrate.
6. The method according to claim 1, wherein, the substrate from
which the washing liquid has been removed in the step (b) is
directly subjected to the step (c) for forming a thin film.
7. The method according to claim 1, wherein, in the step (c), the
substrate is washed with an inert gas in the form of plasma before
the thin film is formed.
8. An apparatus for manufacturing a semiconductor device having a
thin film on a substrate, comprising: a washing section for washing
the substrate with a washing liquid; a liquid-removing section for
removing the washing liquid from the substrate by blowing
compressed air to the substrate washed; and a film-forming section
for forming a thin film on the substrate from which the washing
liquid has been removed.
9. The apparatus according to claim 8, wherein the washing section
comprises a brush washing section, a rinse section, and an
ultrasonic washing section, in which the substrate is washed.
10. The apparatus according to claim 8, wherein the liquid-removing
section has an air knife which is inclined to the direction
perpendicular to a transfer direction of the substrate and the
vertical direction so as to blow compressed air to the back of the
substrate transfer direction.
11. The apparatus according to claim 10, further comprising a
heater for heating compressed air to be supplied to the air
knife.
12. The apparatus device according to claim 10, further comprising
an ionizing section for ionizing the compressed air to be supplied
to the air knife.
13. The apparatus according to claim 8, wherein the liquid-removing
section has at least two air knives located above and below
substrate to be transferred, inclined to the direction
perpendicular to the substrate transfer direction and arranged such
that the closest ends of adjacent air knives are spaced apart at a
predetermined interval in the substrate transfer direction and
overlap for a predetermined distance in the direction perpendicular
to the substrate transfer direction.
14. The apparatus according to claim 8, wherein the film forming
section comprises a film forming chamber for forming a film on the
substrate and a load-lock chamber for heating the substrate to a
predetermined temperature before the film is formed in the film
forming chamber.
15. The apparatus according to claim 8, wherein a first supply pipe
for supplying a material gas for forming a film and a second supply
pipe for supplying an inert gas which is ionized, into a plasma
before the film is formed, are connected to the film forming
chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Applications No. 11-139820,
filed May 20, 1999; No. 11-228521, filed Aug. 12, 1999; and No.
11-280266, filed Sep. 30, 1999, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method and apparatus for
manufacturing a semiconductor device made by forming a thin film on
a substrate, such as a thin-film photovoltaic module.
[0003] To manufacture a thin-film photovoltaic module, for example,
a thin film such as a semiconductor film or a metal film is formed
on a substrate made of glass and having a transparent electrode
formed on it.
[0004] When the thin film is formed on the substrate, particles may
be attached to the substrate. If this happens, defects will
develop. Therefore, the substrate is usually washed before the thin
film is formed on the substrate in order to remove the
particles.
[0005] When the washed substrate is left to stand and is thereby
dried, the washing liquid attached to the substrate may form a
water mark (stain). The substrate is therefore forcibly dried after
the washing.
[0006] To dry the washed substrate, a clean oven is used in a
conventional method. The clean oven is designed such that clean air
is introduced into the interior. In the clean oven, the air is
heated by a heater and circulated.
[0007] Therefore, if the washed substrate is placed in the clean
oven, it can be dried with the heated air circulating in the clean
oven.
[0008] As indicated above, the clean oven is designed to dry the
substrate while the heated air is circulated, oven is clean, hence,
the air gradually contain with particles remaining in the clean
oven even if it is clean when introduced into the clean oven.
[0009] It is therefore easy for particles to attach to the
substrate dried in the clean oven. Consequently, defects are likely
to develop in the thin film formed on the substrate.
BRIEF SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a method
and apparatus for manufacturing a semiconductor device,
characterized in that a washed substrate is free of contamination
while it is being dried.
[0011] To achieve the object, a method of manufacturing a
semiconductor device, wherein a thin film is formed on a substrate,
comprises the steps of:
[0012] (a) washing the substrate with a washing liquid;
[0013] (b) removing the washing liquid from the substrate by
blowing a compressed air to the substrate washed; and
[0014] (c) forming a thin film on the substrate immediately after
the step (b), without performing to another step.
[0015] In the method, the substrate is dried with clean air by
blowing compressed air to the substrate. Contamination of the
substrate can be prevented in the drying process.
[0016] Other objects and advantages of the present invention will
become apparent from a consideration of the following Detailed
Description of the Invention. The objects and advantages of the
present invention can be attained by the constitutions clearly set
forth in the accompanying claims or combination of the
constitutions.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0017] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0018] FIG. 1 is a view showing an apparatus for manufacturing a
semiconductor device, according to a first embodiment of the
present invention;
[0019] FIG. 2 is a schematic view showing the washing section of
the apparatus;
[0020] FIG. 3 is a schematic plan view of the liquid removing
section of the apparatus;
[0021] FIG. 4 is a side view of the liquid removing section;
[0022] FIG. 5 is a schematic view of the film forming section of
the apparatus;
[0023] FIG. 6 is a cross sectional view of the substrate having a
thin film subjected to scribing;
[0024] FIG. 7 is a schematic side view of a washing unit according
to a second embodiment of the invention;
[0025] FIG. 8 is an enlarged view of part A of FIG. 7;
[0026] FIG. 9 is a schematic perspective view of the air blower
mechanism of the washing unit;
[0027] FIG. 10 is a schematic perspective view of an air blower
mechanism according to a third embodiment of the invention;
[0028] FIG. 11 is a plan view of a liquid removing section
according to a fourth embodiment of the present invention; and
[0029] FIG. 12 is a side view of the liquid removing section.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Embodiments of the present invention will be described with
reference to the accompanying drawings.
[0031] FIG. 1 shows an apparatus of manufacturing a semiconductor
device, which is the first embodiment of the invention. The
apparatus has a washing section 1, a liquid-removing section 2, and
a film forming section 3.
[0032] The washing section 1 is designed to wash a glass substrate
10 having a transparent conducting film formed thereon and used as
an electrode film, as shown in FIGS. 2, 3 and 4. The substrate 10
is a component of a semiconductor device, more precisely a thin
film type photovoltaic module. The substrate is washed in the
washing section 1 and dried in the liquid removing-section 2.
Thereafter, a thin film, such as a semiconductor film or a metal
film, is formed on that surface of the substrate on which an
electrode film is provided (hereinafter, referred to as "upper
surface"), in the film forming section 3.
[0033] As shown in FIGS. 2 and 3, a transfer mechanism 5 is
provided in the washing section 1 and the liquid removing-section
2. The transfer mechanism 5 comprises a plurality of transfer
rollers 4. The transfer mechanism 5 transfers the substrate 10 from
the washing section 1 to the liquid removing section 2.
[0034] As shown in FIG. 2, the washing section 1 comprises a brush
washing section 6, a rinse section 7, and an ultrasonic washing
section 8. The sections 6, 7, and 8 are arranged in the direction
of transferring the substrate 10.
[0035] The brush washing section 6 has a pair of washing brushes 9
and a nozzle body 11. The brushes 9 in contact the upper and lower
surfaces of the substrate 10, respectively, which is to be
transferred by the transfer roller 4. The nozzle body 11 supplies
washing liquid such as detergent or pure water to a position where
the washing brushes 9 contact the substrate 10. The upper surface
of the substrate 10 is brush-washed with the washing liquid.
[0036] The nozzle body 11 is a tube 11a longer than the width of
the substrate 10. The tube 11a has a plurality of nozzle holes 11b
arranged at predetermined intervals.
[0037] In this embodiment, the washing liquid is supplied by the
nozzle body 11 to only both upper and lower surfaces of the
substrate 10 on which the thin film is to be formed. Nevertheless,
the nozzle body 11 may be located only above the substrate 10 to
wash the upper surface only.
[0038] The rinse section 7 has a rinse vessel 12. The rinse vessel
12 has a loading port 13 and an unloading port 14, the loading port
13 is made in the side wall positioned at the upstream of the
transfer path of the substrate 10. The unloading port 14 is made in
the opposite side wall positioned at the downstream of the transfer
path. The loading port 13 and the unloading port 14 are formed at
almost the same level as that of the substrate 10 to be transferred
by the transfer roller 4.
[0039] Within the rinse vessel 12, the transfer roller 4
constituting the transfer mechanism 5 is arranged at the same level
as that of the transfer roller 4 arranged outside. The mechanism 5
can transfer the substrate 10 through the loading port 13 into the
rinse vessel 12 and from the vessel 12 through the unloading port
14, as shown by arrows in FIGS. 1 and 2.
[0040] Into the rinse vessel 12 rinse liquid such as pure water is
supplied by the supply nozzle (not shown). The rinse liquid flows
out of the rinse vessel 12 through the loading port 13 and the
unloading port 14. The rinse liquid is supplies into the rinse
vessel 12 at a rate equal to or slightly higher than the rate at
which the liquid blows out through the loading port 13 and the
unloading port 14.
[0041] With this mechanism, the surface of the rinse liquid in the
rinse vessel 12 can be maintained at a higher level than the
substrate 10. Thus, the substrate 10 is transferred in the rinse
liquid. Therefore, the upper surface of the substrate 10 passing
through the rinse vessel 12 is rinsed with the rinse liquid without
fail. Furthermore, the particles washed out from the substrate 10
by the rinse treatment are rarely left in the rinse vessel 12. This
is because the rinse liquid is always allowed to flow out from the
loading port 13 and the unloading port 14.
[0042] In this embodiment, a single rinse vessel is used.
Nevertheless, a plurality of rinse vessels may be arranged in the
transfer direction of the substrate 10 to rinse more reliably the
substrate 10 washed with the washing liquid.
[0043] The substrate 10 rinsed in the vessel 12 is washed in the
ultrasonic washing section 8 having a washing vessel 15. The
washing vessel 15 has a loading port 16 made in the side wall
positioned at the upstream of the transfer path of the substrate
10. The vessel 15 has an unloading port 17 made in the opposite
side wall positioned at the downstream of the transfer path. Both
ports 16 and 17 are at substantially the same level as the
substrate 10 to be transferred.
[0044] Inside the washing vessel 15, the transfer rollers 4 are
arranged in the same manner as in the rinse vessel 12. An
ultrasonic generator 18 for generating an ultrasonic vibration of
about 20-40 kHz is provided at the bottom portion. Pure water is
supplied into the washing vessel 15 as the washing liquid. The
ultrasonic vibration generated by the ultrasonic wave generator 18
is applied to the washing liquid.
[0045] The rate of supplying the washing liquid is almost equal to
or slightly larger than the rate at which the liquid flows out
through the loading port 16 and unloading port 17. As mentioned
above, the surface of the washing liquid in the washing vessel 15
is slightly higher than the upper surface of the substrate 10 to be
transferred by the transfer rollers 4. Therefore, both upper and
lower surfaces of the substrate 10 can be washed by the washing
liquid vibrated by the ultrasonic wave.
[0046] In addition, since a part of the washing liquid flows from
the loading port 16 and the unloading port 17, the particles
removed from the substrate 10 by the ultrasonic washing can to flow
out, too.
[0047] The substrate 10 washed in the ultrasonic washing section 8
is dried in the liquid-removing section 2 shown in FIGS. 3 and 4.
The solution-removing section 2 is constituted of a pair of air
knives 21 which face the upper and lower surfaces of the substrate
to be transferred. To the air knife 21, compressed air cleaned by a
filter is applied through a pipe 19.
[0048] Onto the pipe 19, there are provided a heater 20 for heating
the compressed air and an ionizing portion 23 for ionizing the
compressed air. Note the compressed air is set at a pressure of
about 5 kg/cm.sup.2 by a pressure control valve 24 attached to the
pipe 19. The air knives 21 are longer than the width of the
substrate 10. As shown in FIGS. 3 and 4, each air knife 21 has a
slit 22 extending along almost all length of the knife and opening
at an edge thereof. The slits 22 of the air knives 21 face the
upper or lower surface of the substrate 10, respectively.
[0049] Each air knife 21 is inclined at a predetermined angle
.alpha. to the transfer direction X of the substrate. The
compressed air is applied through the slit 22 in a direction Z
inclined at an angle .beta. to the direction V perpendicular to the
transfer direction X, as shown in FIG. 3.
[0050] The compressed the air applied to each air knife 21 is blown
toward the upper or lower surface of the substrate 10 from the slit
hole 22. The washing liquid on the upper and lower surfaces of the
substrate 10 is thereby pushed toward the rear edge of the
substrate 10 in the transfer direction of the substrate, as
indicated by an arrow Y in FIG. 3. As a result, the washing liquid
falls dropwise and smoothly from the end of the substrate. Thus,
the washing liquid is removed from the substrate 10.
[0051] The compressed air to apply to the air knife is heated by
the heater 20 to a temperature higher than room temperature, for
example, to about 40-50.degree. C. Therefore, the washing liquid is
removed from the substrate 10 by force of the compressed air, and
the substrate 10 is dried with heat of the compressed air.
Therefore, the substrate 10 can be efficiently dried without
fail.
[0052] Even if the compressed air is not heated, the substrate can
be dried to a predetermined degree. On the other hand, if the
compressed air is ionized and applied to the substrate 10, the
substrate 10 can be prevented from being electrically charged
during the drying process. As a result, no static electricity will
be generated, no particles will be attached to the substrate 10.
Hence, the substrate 10 is not contaminated during the drying
process.
[0053] The substrate 10 dried in the solution-removing section 2 is
immediately transferred to the film forming section 3. More
specifically, the substrate 10 is unloaded by the transfer rollers
4 and transferred to the film forming section 3 by a robot (not
shown). In other words, the substrate 10, from which the washing
liquid has been removed, is directly transferred to the film
forming section 3 without being subjected to any other process.
[0054] The substrate 10 dried in the liquid removing section 2 and
unloaded therefrom is continuously loaded into the film forming
section 3. Therefore, the chance for the particles in the
atmosphere to attach to the dried substrate 10 are small. The
substrate 10 is transferred to the film forming process 3, while
kept clean.
[0055] Furthermore, the substrate 10 is dried with the compressed
air, not in a clean oven as in the conventional method. The drying
process can therefore be performed immediately after the washing
process.
[0056] Therefore, unlike the case where the washed substrates 10
are dried in batches in a clean oven, the time elapsing between the
washing process and the drying process can be reduced. It is
therefore possible to prevent the washing liquid applied to the
substrate 10 during the washing process, from partially being dried
before the dry process to make a water mark (stain) onto the
substrate 10.
[0057] The film forming section 3 has a film forming chamber 25 as
shown in FIG. 5. The film forming chamber 25 is used for forming a
thin film on the upper surface of the substrate 10 by a plasma
process (CVD). The film forming chamber 25 has a loading port 26 in
one side and an unloading port 27 in the opposite side. Provided in
the film forming chamber 25 are a table 28 and a high frequency
electrode 29. The table 28 incorporates a heater 28a. The electrode
29 is arranged, facing the upper surface of the table 28.
[0058] Furthermore, two supply pipes 31 and 32 are connected to the
upper portion of the film forming chamber 25. The first supply pipe
31 is used to supplies material gas. The second supply pipe 32 is
provided for supplying an inert gas into the film formation chamber
25. To the bottom of the chamber 25, an exhaust pipe 34 having a
vacuum pump 33 is connected.
[0059] At the loading port 26 of the film forming chamber 25, a
load-lock chamber 35 is arranged. At the unloading port 27 of the
chamber 25, an unload-lock chamber 36 is arranged. The chambers 35
and 36 have loading ports 35a and 36a and unloading ports 35b and
36b, respectively.
[0060] A pre-heater 37 and a support table 38 are arranged in the
load-lock chamber 35. An exhaust duct 40 having a vacuum pump 39 is
connected to the bottom of the load-lock chamber 35.
[0061] The unloading port 35a of the load-lock chamber 35 and the
loading port 26 of the film forming chamber 25 are connected
airtight by a first connecting body 41. The unloading port 27 of
the film forming chamber 25 and the loading port 36 of the
unload-lock chamber 36 are connected airtight by way of a second
connection body 42.
[0062] The loading ports and the unloading ports of the chambers
25, 35 and 36 are closed airtight by valves 43. The first and
second connecting bodies 41 and 42 incorporate transfer robots (not
shown). Furthermore, a mounting table 44 is arranged in the
unload-lock chamber 36. An exhaust duct 46 having an vacuum pump 45
is connected to the bottom of the chamber 36.
[0063] When the substrate 10 dried in the liquid removing section 2
is placed on the support table 38 in the load-lock chamber 35, the
loading port 35a is closed and the load-lock chamber 35 is
depressurized. Simultaneously, the substrate 10 is pre-heated by
the pre-heater 37. During the preheating, the load-lock chamber 38
is depressurized by the vacuum pump 39.
[0064] When the substrate 10 is pre-heated, the loading port 35a of
the load-lock chamber 38 is closed and the unloading port 35b is
opened. Subsequently, the robot arranged in the first connecting
body 41 enters the load-lock chamber 35 and receives the substrate
10 from the holding table 38.
[0065] At the same time, the unloading port 35b of the load-lock
chamber 35 is closed airtight by the valve 43. Simultaneously, the
loading port 26 of the film forming chamber 25 is opened. The
substrate 10 preheated is placed onto the table 28 in the film
forming chamber 25 by the robot arranged in the first connection
body 41. Then, the robot moves back. Thereafter, the loading port
26 is closed, and the film formation chamber is depressurized by
the vacuum pump 33.
[0066] When the film forming chamber 25 is depressurized to a
predetermined pressure, an inert gas is supplied from the second
supply pipe 32 into the chamber 25. Simultaneously, high frequency
power is supplied to a high frequency electrode 29, activating the
inert gas. The gas activated has a cleaning function. The substrate
10 washed in the washing section 1 is therefore further cleaned
with the inert gas.
[0067] When the substrate 10 is cleaned with the inert gas for a
predetermined time, material gas is supplied, in place of the
insert gas, from the first supply pipe 31 into the film forming
chamber 25. The material gas is reacted in a plasma generated by
supplying a high frequency power to the high frequency electrode
29.
[0068] As a result, a solid substance generated in the reaction is
deposited on the upper surface of the substrate 10, forming a thin
film on the upper surface of the substrate 10.
[0069] The substrate 10 is washed in the washing section 1 and then
transferred to the solution-removing section 2, in which the
substrate 10 is dried without contamination. Thereafter, the
substrate 10 is transferred to the film forming chamber 25.
[0070] Since no particles are contained in the thin film deposited
on the substrate 10, it is possible to prevent defects from
developing in the thin film. As a result, the semiconductor device
can be manufactured in a high yield.
[0071] In the case of a photovoltaic module having 50 cells
connected in series, manufactured by employing the clean oven in a
conventional drying process of the substrate 10, 40 cells are
defective as experiments shows. In the case of the photovoltaic
module according to the present invention wherein the substrate 10
has been dried with the compressed air, defects were developed in
only 10 or less cells.
[0072] To detect whether or not a cell has defects, a reverse
voltage is applied to the cell. If the particles are contained in
the film during the film forming process, they cause a short
circuit. Whether defects have developed or not can be determined in
accordance with whether the applied voltage changes or not.
[0073] When the film formation on the substrate 10 is completed,
the unloading port 27 of the film forming chamber 25 is opened, and
a robot moves from the second connecting body 42 and enters the
film forming chamber 25 and receives the substrate 10.
Simultaneously, the loading port 36a of the unload-lock chamber 36
is opened.
[0074] The robot loads the substrate 10, on which a film is formed
in the film forming chamber 25, into the unload-lock chamber 36 and
mounts it on a mounting table 44. Thereafter, the robot moves back
to the second connecting body 42. Simultaneously, the unloading
port 27 of the film forming chamber 25 and the loading port 36a of
the load-lock chamber 36 are closed.
[0075] In this embodiment, the load-lock chamber 35 and unload-lock
chamber 36 are connected airtight at the loading port 26 and the
unloading port 27 of the film forming chamber 25, respectively. By
virtue of this structural feature, the substrate 10 can be
transferred without significantly degrading the depressurized state
of the film forming chamber 25.
[0076] The substrate 10 mounted on the mounting table 44 of the
unload-lock chamber 36 is taken out by a robot (not shown) placed
outside the unloading port 43 of the chamber 36. The substrate 10
is then subjected to the next process.
[0077] The present invention is not limited to the aforementioned
embodiment. For example, a single brush washing unit, a single
rinse unit and a single ultrasonic washing unit, all used in the
washing section in the aforementioned embodiment, however, may each
be replaced by a plurality of units. Further, the three types of
washing units used in combination may be replaced by one or two
types of washing units.
[0078] A nozzle washing unit for applying the ultrasonically
vibrated washing liquid from the nozzle to the substrate may be
combined with the aforementioned washing units or may be used
alone.
[0079] A single load-lock chamber for preheating the substrate and
maintaining the reduced pressure state of the film formation
chamber is placed at the upstream of the film formation chamber in
the film forming section. Nonetheless, a plurality of load-lock
chambers may be used to perform a series of processes on the
substrate continuously, without waiting time, if the efficiency in
preheating the substrate is improved and if each of the periods
required for the washing section and the liquid removing section is
equal to the period required to form the film formation in the film
forming section.
[0080] The semiconductor device of the present invention is not
limited to a photovoltaic module. Rather, it may be a liquid
crystal display panel and a semiconductor wafer. In short, the
present invention can be applied to any case where a thin film is
formed on the substrate.
[0081] In the film forming section 3 shown in FIG. 1, a transparent
conducting film 51, a semiconductor film 52 for use in photovoltaic
conversion, and a rear surface electrode film 53 are stacked on
upon another, on the substrate 10 as shown in FIG. 6. When these
films are stacked, each of the films are scribed as is indicated by
a scribe line 54 in the figure. The scribe lines are formed by a
laser beam.
[0082] When the thin film is scribed with the leaser beam,
particles of debris are generated. The particles are attached to
the substrate 10 and remain thereon. The particles remaining on the
substrate 10 sometimes cause defects in the thin film formed next
thereon.
[0083] It is necessary to wash the substrate 10 after the
transparent conducting film 51 is formed and scribed, after the
semiconductor film 52 is formed on the transparent conducting film
51 and scribed, and after the rear surface electrode 53 is formed
and scribed.
[0084] FIGS. 7 to 9 show a second embodiment of the present
invention. This embodiment is a washing unit for washing the
substrate 10 after the transparent conducting film 51 is formed on
the substrate 10 and scribed, after the semiconductor film 52 for
photovoltaic conversion is formed and scribed, and the rear surface
electrode film 53 is formed and scribed.
[0085] Now, the washing unit will be explained. FIG. 7 is a
schematic vertical longitudinal sectional view of the washing unit
for the substrate 10 for a photovoltaic module. FIG. 8 is an
enlarged sectional view of portion A of FIG. 7. FIG. 9 is a
perspective view of an air blower mechanism.
[0086] The washing unit for washing the substrate 10 has a base
111. A washing vessel 112 is provided on the base 111. A loading
port 113 for the substrate 10 is made in the side wall at one of
the washing vessel 112. The wall at the other end has an unloading
port 114. A roller conveyer 115 is provided as a transfer
mechanism, both inside and outside the washing vessel 112 at the
substantially the same level as the loading port 113 and the
unloading port 114. The roller conveyer 115 transports the
substrate 10 horizontally. While the substrate 10 is being so
transported, its surface, on which a transparent electrode 51 is
formed, remains turned upward.
[0087] The rollers 115a constituting the roller conveyer 115 are
rotated by a rotation-drive mechanism (not shown). With this
rotation, the substrate 10 is loaded into the washing vessel 112
through the loading port 113 and unloaded through the unloading
port 114.
[0088] A loading section 116 is provided at the loading port 113 of
the washing vessel 112, for loading the substrate 10 unwashed. An
unloading section 117 is provided at the unloading port 114, for
unloading the substrate 10 washed. The roller conveyer 115 extends
from the loading section 116 to the unloading section 117.
[0089] The bottom of the washing vessel 112 has a pure water supply
port 118 for supplying, for example, pure water W. The pure water
port 118 is connected to a pure water source (not shown).
Furthermore, an ultrasonic oscillator 119 (output 0.2 to 1.0
W/cm.sup.2) is provided on the inner bottom of the washing vessel
112.
[0090] A plurality of rotating brushes 120 and high-pressure air
nozzles 121 are arranged above the roller conveyer 115. The
rotation brush 120 comprises a rotation shaft 120a rotated by the
rotation drive mechanism (not shown) and a nylon bristle 120b
planted around the rotation shaft 120a and configured in the roll
form.
[0091] The rotation brush 120 is provided for removing particles
such as debris and burr remaining inside the scribe line 54, by
rubbing the substrate 10 and the scribe line 54 with the tip of the
bristle 120b onto. To the portion rubbed and scribed by the
rotation brush 120, high-pressure air is applied from the high
pressure air nozzle 121, thereby blowing the particles away.
[0092] Furthermore, an air knife 122 is provided at the unloading
port 114 of the washing vessel 112, for blowing pure water W and
particles from the upper and lower surfaces of the substrate
10.
[0093] Note that the purity of the water present in the pure water
supply source or at an output port of a pure water producing unit
is as follows:
[0094] Resistivity: 16-18 M.OMEGA..multidot.cm (25.degree. C.)
[0095] The number of fine particles of 0.2 .mu.m or more:
100-150/ml
[0096] The number of viable bacteria: 0-10/ml
[0097] Organic material: 0.5 to 1.0 ppm.
[0098] As shown in FIGS. 8 and 9, an air blower mechanism 123 is
provided in the unloading section 117 of the washing vessel 112,
for blowing a high pressure air to an outer peripheral portion 10a
of the substrate 10 to be transferred by the roller conveyer
115.
[0099] The air blower mechanism 123 has a nozzle main body 125. The
body 125 has the same rectangular frame form as the outer
peripheral portion 10a of the substrate 10 and has an air passage
124 inside. The lower surface of the nozzle main body 125 has a
plurality of nozzle holes 126 for spraying high pressure air to the
outer peripheral portion 10a of the substrate 10.
[0100] The air blower mechanism 123 is provided above the substrate
10 placed on the roller conveyer 115. The air passage 124 is
connected to a high pressure air source (not shown) by the air
supply pipe 127.
[0101] How the substrate 10 is washed by the washing apparatus
mentioned above will be described. Pure water W is supplied via the
pure water supply port 118 to the washing vessel 112. When the pure
water W reaches the level of the loading port 113 and the unloading
port 114, it water W starts flowing out through the loading port
113 and the unloading port 114. Therefore, the level of the pure
water W in the washing vessel 112 remains constant. When power is
supplied to the ultrasonic oscillator 119, ultrasonic vibration is
transmitted to the pure water W.
[0102] When the substrate 10 is mounted on the roller conveyer 115
of the unloading section 116, the substrate 10 is transferred
toward the loading port 113. When the substrate 10 is moved into
the pure water W of the washing vessel 112 by the roller conveyer
115, particles such as debris and burr are removed from the scribe
line 54 of the substrate 10. This is because the pure water W is
ultrasonically vibrated. The particles removed are discharged along
with the flowing-out water or precipitated in the pure water W.
Therefore, no particles are attached again to the substrate 10. It
is therefore possible to effectively reduce the contamination of
the washing vessel 112 with particles.
[0103] The substrate 10 is washed while being transferred.
Therefore, a plurality of substrates 10 are continuously washed.
Furthermore, the entire surface of the substrate can be uniformly
and ultrasonically vibrated since the substrate 10 moves above the
ultrasonic oscillator 119.
[0104] The washed substrate 10 is unloaded from the unloading port
114 of the washing vessel 112 to the unloading section 117. The
pure water W and the particles are removed from the upper and the
lower surfaces of the substrate 10 unloaded from the unloading port
114 as the high pressure air is blown from the air knife 122. The
substrate 10 can be continuously washed and dried.
[0105] When the substrate 10 washed is conveyed to the unloading
section 117 by the roller conveyer 115, high pressure air is blown
to the substrate 10 from the blow nozzle holes 126 of the air blow
mechanism 123. The nozzle main body 125 has the same rectangular
frame form as the outer peripheral portion of the substrate 10.
[0106] Since the high pressure air is strongly blown to the
periphery 10a of the substrate 10, the water drops can be removed
from the outer periphery 10a of the substrate 10, i.e., four sides
thereof.
[0107] The high pressure air can be blown to the periphery 10a of
the substrate 10, while the substrate 10 is being transferred by
the roller conveyer 115. When the substrate 10 faces the air blower
mechanism 123, the roller conveyer 115 is stopped in a stop B zone
shown in FIG. 8. The high pressure air can therefore be intensively
blown to the periphery 10a of the substrate 10.
[0108] Note that the air blower mechanism 123 (not shown) may be
moved for a predetermined time in synchronism with the movement of
the substrate 10 transferred by the roller conveyer 115.
[0109] FIG. 10 shows a modified example of the air blower mechanism
128 according to a third embodiment.
[0110] At the unloading section 117 of the washing vessel 112,
upper-stage pulleys 130a, 130b, 130c are provided for a first
corner portion 129a, a second corner portion 129b, and a third
corner portion 129c, respectively. An upper-stage endless belt 131
is wrapped around these upper-stage pulleys 130a, 130b, 130c.
[0111] Lower-stage pulleys 132a, 132b, 132c are provided
respectively at the portions facing the first corner portion 129a,
a fourth corner portion 129d and the third corner portion 129c. A
lower-stage endless belt 133 is wrapped around the lower-stage
pulleys 132a, 132b, 132c.
[0112] The upper-stage pulley 130a and the lower-stage pulley 132a,
which are provided at the first corner portion 129a, are supported
coaxial with the upper-stage pulley 130c and the lower stage pulley
132c which are provided at the third corner portion 129c. A motor
134 is connected to the shaft of the upper-stage pulley 130a and
the lower-stage pulley 132a, both provided at the first corner
portion 129a.
[0113] The air applying nozzles 135a and 135b are attached
respectively to parts of the upper stage endless belt 131 and the
lower stage endless belt 133. The air applying nozzles 135a and
135b are connected to a high pressure air supply source.
[0114] Since the air blower mechanism 128 is thus constructed, the
upper-stage endless belt 131 and the lower-stage endless belt 133
are moved in the directions indicated by arrows, respectively, when
the upper pulley 130a and the lower pulley 132a are rotated by the
rotation of the motor 134.
[0115] Therefore, the air spray nozzle 135a moves along the two
sides of the substrate 10, which define the second corner portion
129b of the substrate 10. The air applying nozzle 135b moves along
the two sides of the substrate 10, which define the fourth corner
portion 129d of the substrate 10. When a high-pressure air is blown
from the air applying nozzles 135a and 135b, the high-pressure air
is blown intensively toward the periphery 10a of the substrate 10,
i.e., the four side surfaces thereof. It is therefore possible to
blow water drops from the periphery 10a of the substrate 10.
[0116] The high pressure air is blown to the periphery 10a of the
substrate (i.e., the four side surfaces thereof) while the
substrate 10 is transferred by the roller conveyer 115.
Alternatively, the air can be blown intensively to the periphery
10a of the substrate 10 by stopping the roller conveyer 115 at the
stop zone B when the substrate 10 faces the air blower mechanism
123.
[0117] In the third embodiment, the air applying nozzles 135a and
135b-are moved along the periphery 10a of the substrate 10 (i.e.,
the four side surfaces) by the pulleys and the endless belts. As
the mechanism for driving the nozzles 135a and 135b, a ball-screw
mechanism and a linear motor may be used. Nonetheless, the drive
mechanism is not limited to this type.
[0118] In the second and third embodiments, the roller conveyer 115
is used to transport the substrate 10. The substrate may be
transferred by a water-permeable endless belt made in the form of a
mesh or a ladder.
[0119] The washing liquid is not limited to pure water W. Tap water
or a chemical washing liquid may be used. The chemical washing
liquid used may be water containing a detergent or organic solvent
such as acetone, methanol, ethanol, trichloroethylene or Freon.
[0120] In the second and third embodiments shown in FIGS. 7 to 10,
a substrate is washed which has, on one surface, a transparent
conducting film with a scribe line formed by a laser beam. The
substrate to be washed is not limited to this. The washing
apparatuses according to the second and third embodiments can wash
a substrate which has a semiconductor film and a rear surface
electrode successively formed on a transparent conducting film and
scribed by a laser beam.
[0121] The air blower mechanisms of the second and third
embodiments may be arranged at downstream of the liquid removing
section 2 of the first embodiment. With this arrangement, the
washing liquid can be removed without fail even if the washing
liquid remains on the periphery of the substrate after the
substrate is dried in the liquid removing section 2.
[0122] FIGS. 11 and 12 show a liquid removing section 210 according
to a fourth embodiment which can be used in place of the liquid
removing section 2 of the first embodiment and the water removing
air knife 122 of the second embodiment.
[0123] As shown in FIG. 11, the substrate 10 is washed, after the
transparent conducting film 51, semiconductor film 52, or rear
surface electrode film 53 is laser-scribed. The substrate 10 is
transferred to the liquid removing section 210 by the transfer
roller 206, with the scribe lines 55 (only some of the scribe lines
are shown in FIG. 11) arranged perpendicular to the transfer
direction indicated by an arrow X.
[0124] In the liquid removing section 210, three air knives 207a,
207b and 207c are arranged in the order mentioned, from the upper
portion to the lower portion. The air knives incline to the
direction perpendicular to the substrate transfer direction X. In
other words, they cover the substrate 10 over the entire width
thereof.
[0125] As shown in FIG. 11, the distance D from one end of the air
knife 207a to the other end of the air knife 207c along the
substrate transfer direction exceeds interval R of-adjacent
transfer rollers 206. Furthermore, the air knives incline more to
the direction perpendicular to the substrate transfer than in the
case where a single knife is used.
[0126] The adjacent air knives (207a and 207b, or 207b and 207c in
FIG. 11) are arranged with their most close end portions spaced
apart from each other in the substrate transfer direction and
overlapping in the direction perpendicular to the substrate
transfer direction. More specifically, as shown in FIG. 11, the
lower end of the air knife 207a is spaced apart from the upper end
of the air knife 207b at an interval S in the substrate transfer
direction. Furthermore, the lower end of the air knife 207a and the
upper end of the air knife 207b overlap as shown by symbol L in
FIG. 11. Liquid is removed by blowing compressed air to the
substrate 10 from the slit nozzles 208, each extending over entire
length of air knives 207a, 207b and 207c in the direction indicated
by an arrow P in FIG. 11.
[0127] In this embodiment, three air knives 207a, 207b and 207c are
arranged in excess of the interval R between the adjacent transfer
rollers 206 and greatly inclined to the direction perpendicular to
the substrate transfer direction. Furthermore, the overlapping
portion L extends in the direction perpendicular to the substrate
transfer direction. With this arrangement, compressed air can be
reliably blown to the region corresponding to the interval R of the
transfer roller 206. Therefore, liquid can be removed from the
substrate 10 sufficiently.
[0128] Since the air knife is greatly inclined, a sufficient force
is generated to blow away the washing liquid from the substrate 10
in the direction perpendicular to the substrate transfer
direction.
[0129] The washing liquid is first pushed away through grooves of
the scribe lines 55 by the compressed air applied from the nozzle
208 of the air knife 207a. When the substrate 10 reaches the mid
portion (interval S) between the air knife 207a and the air knife
207b along the substrate transfer direction, the compressed air is
no longer applied to the washing liquid. The compressed air is not
applied to the washing liquid for a short period of time, and no
force is applied to the washing liquid for this period.
[0130] However, right before the washing liquid starts flowing
reversely, the compressed air applied from the nozzle 208 of the
air knife 207b blows the washing liquid through the grooves of the
scribe lines 55. The liquid is blown in a similar manner by the air
knives 207b and 207c.
[0131] When the compressed air is applied, the washing liquid forms
waves in the grooves of the scribe lines 55. The waves are not so
high. Therefore, when the waves become-low in the middle region
(interval S) between the air knives, not breaking or scattering,
the washing liquid is made to flow again, by the compressed air
blown from the next air knife. With this mechanism, the washing
liquid is successfully removed from the substrate 10.
[0132] It is possible to improve the photovoltaic conversion
efficiency of the photovoltaic module, because the waves of the
particle-containing washing liquid do not break to wet the region
from which water has been completely removed.
[0133] The photovoltaic modules manufactured by using the substrate
10 washed in the method according to this embodiment were tested
for current/voltage characteristics by using 1.5 solar simulator
(AM=1.5, 100 mM/cm.sup.2). As a result, the fill factor (FF) was
67%. On the other hand, the photovoltaic module manufactured by
using the substrate 10 washed by a conventional method had a fill
factor (FF) of 65%. Hence, the washing method of this embodiment is
effective in improving the photovoltaic conversion efficiency of
the photovoltaic module.
[0134] "AM" used herein stands for "Air Mass," which indicates a
solar spectrum, and more specifically, the thickness of the
atmospheric layer through which a solar light passes. For example,
AM is 0 in the space and 1 right at the equator. "FF" used herein
stands for "Fill Factor." The maximum value of V.times.I on the VI
curve of a photovoltaic module is denoted by "Pmax." FF is a value
obtained by dividing Pmax by a product of multiplying an open
circuit voltage (Voc) and short circuit current (Ise).
[0135] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents
* * * * *