U.S. patent application number 14/487398 was filed with the patent office on 2015-01-01 for wafer separation method, wafer separation and transfer method, and solar cell wafer separation and transfer method.
The applicant listed for this patent is KABUSHIKI KAISHA WATANABE SHOKO. Invention is credited to Ichiki KUSUHARA, Kyouhei TSUNASHIMA.
Application Number | 20150004741 14/487398 |
Document ID | / |
Family ID | 42339821 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150004741 |
Kind Code |
A1 |
KUSUHARA; Ichiki ; et
al. |
January 1, 2015 |
WAFER SEPARATION METHOD, WAFER SEPARATION AND TRANSFER METHOD, AND
SOLAR CELL WAFER SEPARATION AND TRANSFER METHOD
Abstract
A wafer separation apparatus improves wafer separation
performance in separation and transfer and suppresses the
occurrence of wafer breakage in separation and transfer, while
remaining inexpensive and small. The apparatus includes: a cassette
that vertically accommodates a large number of single wafers in
intimate contact with each other, the cassette being at least
vertically opened; a cassette support that removably supports the
cassette, the cassette support being at least vertically opened; a
hoisting unit that hoists and lowers the cassette support
integrally with the cassette; a liquid bath that accommodates a
liquid into which the cassette support is immersed integrally with
the cassette when the hoisting unit descends; a nozzle in the
inside of the liquid bath to issue micro bubbles from the underside
of the cassette support toward a large number of the wafers; and a
micro bubble generator that generates micro bubbles to be issued
from the nozzle.
Inventors: |
KUSUHARA; Ichiki; (Tokyo,
JP) ; TSUNASHIMA; Kyouhei; (Saitama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA WATANABE SHOKO |
Tokyo |
|
JP |
|
|
Family ID: |
42339821 |
Appl. No.: |
14/487398 |
Filed: |
September 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13144198 |
Sep 20, 2011 |
8863957 |
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PCT/JP2010/050233 |
Jan 12, 2010 |
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14487398 |
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Current U.S.
Class: |
438/67 ; 134/18;
134/25.4; 414/801 |
Current CPC
Class: |
B28D 5/0082 20130101;
H01L 31/18 20130101; B65G 59/02 20130101; H01L 21/67057 20130101;
H01L 21/02052 20130101; H01L 21/67092 20130101 |
Class at
Publication: |
438/67 ; 414/801;
134/25.4; 134/18 |
International
Class: |
B28D 5/00 20060101
B28D005/00; H01L 21/02 20060101 H01L021/02; H01L 31/18 20060101
H01L031/18; B65G 59/02 20060101 B65G059/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2009 |
JP |
2009-004709 |
Claims
1. A wafer separation method comprising the steps of: an
accommodating step of vertically accommodating a large number of
single wafers in a cassette in intimate contact with each other,
the cassette being at least vertically opened; a mounting and
supporting step of mounting and supporting the cassette on a
cassette support at least vertically opened; a lowering step of
lowering the cassette support integrally with the cassette using a
hoisting unit and immersing the wafers vertically arranged in a
liquid in an inside of the liquid bath; and a micro bubble issuing
step of issuing micro bubbles generated in a micro bubble generator
from an underside of the cassette support toward the wafers
vertically arranged and causing the micro bubbles to enter and stay
in a large number of the individual wafers.
2. A wafer separation and transfer method comprising: an
accommodating step of vertically accommodating a large number of
single wafers in a cassette in intimate contact with each other,
the cassette being at least vertically opened; a mounting and
supporting step of mounting and supporting the cassette on a
cassette support at least vertically opened; a lowering step of
lowering the cassette support integrally with the cassette using a
hoisting unit and immersing the wafers vertically arranged in a
liquid in an inside of the liquid bath; a micro bubble issuing step
of issuing micro bubbles generated in a micro bubble generator from
an underside of the cassette support toward the wafers vertically
arranged and causing the micro bubbles to enter and stay in each
space between a large number of the wafers; a rotating step of
rotating the cassette support integrally with the cassette to
horizontally arrange a large number of the wafers using a rotating
unit, while the micro bubbles enter and stay in each space between
a large number of the wafers; a hoisting step of hoisting the
cassette support integrally with the cassette as the wafers are
horizontally arranged using the hoisting unit and lifting a topmost
wafer above at least a liquid level of the liquid bath; an
unloading step of unloading the topmost wafer lifted above the
liquid level; and a carrying step of carrying the unloaded
wafer.
3. A wafer separation and transfer method comprising: an
accommodating step of vertically accommodating a large number of
single wafers in a cassette in intimate contact with each other
after removal of the wafers, the cassette being at least vertically
opened; a mounting and supporting step of mounting and supporting
the cassette on a cassette support at least vertically opened; a
pre-washing step of lowering the cassette support integrally with
the cassette using a hoisting unit and pre-washing the wafers
vertically arranged; an unloading and carrying step of unloading
and carrying the cassette after pre-washed; a lowering step of
immersing the carried cassette in a liquid in an inside of a liquid
bath; a micro bubble issuing step of issuing micro bubbles
generated in a micro bubble generator from an underside of the
cassette support toward the wafers vertically arranged and causing
the micro bubbles to enter and stay in each space between a large
number of the wafers; a rotating step of rotating the cassette
support integrally with the cassette to horizontally arrange a
large number of the wafers using a rotating unit, while the micro
bubbles enter and stay in each space between a large number of the
wafers; a hoisting step of hoisting the cassette support integrally
with the cassette as the wafers are horizontally arranged using the
hoisting unit and lifting a topmost wafer above at least a liquid
level of the liquid bath; an unloading step of unloading the
topmost wafer lifted above the liquid level; and a carrying step of
carrying the unloaded wafer.
4. A solar cell wafer separation and transfer method comprising: a
slicing step of slicing a silicon ingot integrally with a support
plate into a large number of wafers; a removing step of removing
the sliced silicon ingot from the support plate for single wafers;
an accommodating step of vertically accommodating a large number of
the single wafers in a cassette in intimate contact with each other
after removal of the wafers, the cassette being at least vertically
opened; a mounting and supporting step of mounting and supporting
the cassette on a cassette support at least vertically opened; a
lowering step of lowering the cassette support integrally with the
cassette using a hoisting unit and immersing the wafers vertically
arranged in a liquid in an inside of the liquid bath; a micro
bubble issuing step of issuing micro bubbles generated in a micro
bubble generator from an underside of the cassette support toward
the wafers vertically arranged and causing the micro bubbles to
enter and stay in each space between a large number of the wafers;
a rotating step of rotating the cassette support integrally with
the cassette to horizontally arrange a large number of the wafers
using a rotating unit, while the micro bubbles enter and stay in
each space between a large number of the wafers; a hoisting step of
hoisting the cassette support integrally with the cassette as the
wafers are horizontally arranged using the hoisting unit and
lifting a topmost wafer above at least a liquid level of the liquid
bath; an unloading step of unloading the topmost wafer lifted above
the liquid level; a carrying step of carrying the unloaded wafer;
and a transfer step of transferring the carried wafer to a solar
cell fabrication apparatus.
5. The wafer separation and transfer method according to claim 2,
comprising: a collecting step of collecting automatically
collecting the carried wafer in the carrying step in a wafer
collection box; and a subsequent step transfer step of
automatically transferring the wafer collection box after collected
to a subsequent step using a multi-robot arm.
6. The solar cell wafer separation and transfer method according to
claim 4, wherein in the transfer step, the wafer is transferred to
a chemical etching apparatus for texture treatment to fabricate a
p-type wafer or n-type wafer.
7. The wafer separation method according to claim 1, wherein in the
micro bubble issuing step, the nozzle or the cassette support is
moved along a direction of arranging the wafers.
8. The wafer separation method according to claim 13, wherein
before starting the micro bubble issuing step, five sides except
the underside of the cassette support is covered with a cover as
the cassette support is immersed in the inside of the liquid
bath.
9. The wafer separation and transfer method according to claim 3,
comprising: a collecting step of collecting automatically
collecting the carried wafer in the carrying step in a wafer
collection box; and a subsequent step transfer step of
automatically transferring the wafer collection box after collected
to a subsequent step using a multi-robot arm.
10. The solar cell wafer separation and transfer method according
to claim 4, comprising: a collecting step of collecting
automatically collecting the carried wafer in the carrying step in
a wafer collection box; and a subsequent step transfer step of
automatically transferring the wafer collection box after collected
to a subsequent step using a multi-robot arm.
11. The wafer separation and transfer method according to claim 2,
wherein in the micro bubble issuing step, the nozzle or the
cassette support is moved along a direction of arranging the
wafers.
12. The solar cell wafer separation and transfer method according
to claim 4, wherein in the micro bubble issuing step, the nozzle or
the cassette support is moved along a direction of arranging the
wafers.
13. The solar cell wafer separation and transfer method according
to claim 5, wherein in the micro bubble issuing step, the nozzle or
the cassette support is moved along a direction of arranging the
wafers.
14. The wafer separation and transfer method according to claim 12,
wherein before starting the micro bubble issuing step, five sides
except the underside of the cassette support is covered with a
cover as the cassette support is immersed in the inside of the
liquid bath.
15. The wafer separation and transfer method according to claim 3,
wherein before starting the micro bubble issuing step, five sides
except the underside of the cassette support is covered with a
cover as the cassette support is immersed in the inside of the
liquid bath.
16. The solar cell wafer separation and transfer method according
to claim 4, wherein before starting the micro bubble issuing step,
five sides except the underside of the cassette support is covered
with a cover as the cassette support is immersed in the inside of
the liquid bath.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wafer separation
apparatus, a wafer separation and transfer apparatus, a wafer
separation method, a wafer separation and transfer method, and a
solar cell wafer separation and transfer method that separate a
batch of single wafers.
BACKGROUND ART
[0002] Patent Document 1: JP09-237770A
[0003] Patent Document 2: JP11-214336A1
[0004] Patent Document 3: JP11-233461A
[0005] In these years, demands for solar cells are rapidly
increasing because of a growing awareness of energy problems such
as exhaustion of fossil fuel sources and environmental problems
such as global warming.
[0006] In these demands, for silicon possibly to be the cells for
solar batteries, such high purity silicon is demanded that the
purity is 99.9999% or more and the resistivity is 0.5 .OMEGA.cm or
more, and off-specification products have been used for raw
materials, which are produced in fabricating high purity silicon
used in semiconductor industries, or in fabricating substrates for
IC, LSI, etc.
[0007] However, particularly in the solar cell, because a single
solar cell module is fabricated using about 54 rectangular silicon
wafers with a five-inch side, the used amount is more enormous than
the used amount of silicon wafers for IC, LSI, or the like, high
purity silicon for semiconductors is expensive, and the yield of
off-specification products is small, causing a problem in that
there is a limit to the amount of silicon materials supplied for
the solar cell.
[0008] In addition, problems have not arisen so far because the
yield of off-specification products of electronic device silicon
exceeds the demand of the solar cell. However, the demand of the
solar cell is exceeding the yield of off-specification products of
electronic device silicon today, causing a serious problem of
shortage of raw materials for solar cell silicon.
[0009] On the other hand, because the solar cell silicon wafer with
a rough surface can surely provide the surface area, the surfaces
of wafers, which are single wafers after a silicon ingot is sliced
with a wire-saw, are not polished in mirror finish like
semiconductor wafers.
[0010] Thus, in the fabrication process of the semiconductor wafer,
a large-sized, expensive separation and transfer apparatus is used
to carry single wafers to a machine for the subsequent process step
(surface finishing process or the like). However, the real
situation in the fabrication process of the solar cell wafer was
that wafers are manually separated one by one without using an
expensive, large-sized separation and transfer apparatus, which
affects product costs as well.
[0011] On the other hand, in consideration of the above-mentioned
problems of shortage of raw materials for solar cell silicon, raw
material costs, or the like, the solar cell wafer is also being
reduced in thickness like the semiconductor wafer, and manual one
by one separation in the fabrication process of the solar cell
wafer tends to cause breakage or the like. Because of this, there
is an increasing demand for small-sized, inexpensive separation
apparatuses.
[0012] Now, a large number of wafers, which are sliced from an
ingot formed in an almost cylindrical shape and attached to a
support plate using a wire-saw, are pre-washed in a pre-washing
device as the wafers are in a cylindrical pack attached to the
support plate in order to remove slurry, cutting dust, or the like.
After the pre-washed wafers are removed from the support plate
using a removing device in order to remove the wafers from the
support plate for single wafers, the wafers are separated into
individual wafers in a separation and transfer apparatus, and then
carried to the subsequent process step.
[0013] At this time, ultrasonic cleaning techniques are known in
which slurry, cutting dust, or the like attached to wafers is
removed with air bubbles generated by a pre-washing device (for
example, see Patent Documents 1 to 3).
[0014] Although ultrasonic washing is effective for washing the
side surfaces and two end surfaces of the silicon ingot, there is a
problem in that it is difficult to cause a washing fluid to reach
the back of the space between the sliced wafers, and slurry,
cutting dust, or the like attached to the wafer surface cannot be
completely removed, resulting in degraded washing effect.
[0015] Then, in removing the pre-washed wafers from the support
plate using the removing device (single wafer separation), they are
immersed in a liquid solution such as acetic acid or the like for
removing the wafers from the support plate and they are
simultaneously subjected to secondary washing for removing
remaining slurry, cutting dust, etc.
[0016] However, the individual single wafers after secondary
washing are in intimate contact with each other in a horizontally
stacked state (piled state) when carried, so that there is a
problem in that it is difficult to reliably perform separating
operations because the initial resistance for separating a
stationary wafer at the topmost position from a wafer therebelow
(directly therebelow) is static frictional resistance greater than
dynamic frictional resistance.
[0017] Then, in the above-mentioned Patent Document 1, there is
disclosed that two jet nozzles that blow water upward are provided
in the inner lower part of a chuter in a separation and transfer
apparatus, pressure water is spouted from the jet nozzles through
the space between the chuter and stacked wafers, and this causes
the topmost wafer to be slightly lifted by the spouted pressure
water when the topmost wafer is carried to the top side of the
chuter for performing smooth wafer separating operations because
the adhesion between the topmost wafer and the wafer directly
therebelow is reduced.
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0018] However, in the above-mentioned separation and transfer
apparatus, problems have arisen that it is likely that wafers are
chipped in blowing pressure water to the wafers, which are being
reduced in thickness, and it is likely that if a wafer in the
subsequent layer is located at the position on the downstream side
of the transfer direction more than a topmost wafer is located, the
second topmost wafer is also floated together with the topmost
wafer and carried together as they are not separated.
[0019] Then, in consideration of the forgoing circumstances, it is
an object of the present invention to provide a wafer separation
apparatus that can improve wafer separation performance in
separation and transfer and can suppress the occurrence of breakage
or the like of wafers in separation and transfer, while the
apparatus is an inexpensive, small-sized apparatus.
Method for Solving the Problems
[0020] A wafer separation apparatus according to the present
invention is characterized by including: a cassette configured to
vertically accommodate therein a large number of single wafers in
intimate contact with each other, the cassette being at least
vertically opened; a cassette support configured to removably
support the cassette, the cassette support being at least
vertically opened; a hoisting unit configured to hoist and lower
the cassette support integrally with the cassette; a liquid bath
configured to accommodate a liquid thereinside into which the
cassette support is immersed integrally with the cassette when the
hoisting unit descends; a nozzle provided in the inside of the
liquid bath for issuing micro bubbles from an underside of the
cassette support toward a large number of the wafers; and a micro
bubble generator configured to generate micro bubbles to be issued
from the nozzle.
[0021] In accordance with the wafer separation apparatus according
to the present invention, it is possible to improve wafer
separation performance, and it is possible to suppress the
occurrence of breakage or the like of wafers, while the apparatus
is an inexpensive, small-sized apparatus.
[0022] A wafer separation and transfer apparatus according to the
present invention is characterized by including: a cassette
configured to vertically accommodate therein a large number of
single wafers in intimate contact with each other, the cassette
being at least vertically opened; a cassette support configured to
removably support the cassette, the cassette support being at least
vertically opened; a hoisting unit configured to hoist and lower
the cassette support integrally with the cassette; a rotating unit
provided on the hoisting unit for rotating the cassette support
integrally with the cassette so as to switch the wafers
accommodated in the cassette between a state in which the wafers
are vertically arranged and a state in which the wafers are
horizontally arranged; a liquid bath configured to accommodate a
liquid thereinside into which the cassette support is immersed
integrally with the cassette when the hoisting unit descends; a
nozzle provided in the inside of the liquid bath for issuing micro
bubbles from an underside of the cassette support toward a large
number of the wafers; a micro bubble generator configured to
generate micro bubbles to be issued from the nozzle; an unloading
member configured to unload a topmost wafer from the horizontally
arranged wafers hoisted from the inside of the liquid bath; and a
carrier unit configured to carry the topmost wafer unloaded by the
unloading member.
[0023] In accordance with the wafer separation and transfer
apparatus according to the present invention, it is possible to
improve wafer separation performance in separation and transfer,
and it is possible to suppress the occurrence of breakage or the
like of wafers in separation and transfer, while the apparatus is
an inexpensive, small-sized apparatus.
[0024] Moreover, the wafer separation and transfer apparatus
according to the invention is characterized in that the carrier
unit includes: a defect determining device provided near an
upstream side of a transfer path for determining a defect on a
wafer being carried; a diverging device provided on a downstream
side of the transfer path more than the defect determining device
for diverging a wafer determined that the wafer has a defect to a
discard route different from a carrying route; and a collecting
device configured to collect a wafer determined that the wafer has
no defect by the defect determining device.
[0025] In accordance with the wafer separation and transfer
apparatus according to the invention, if a separated wafer has any
defects, it is possible to eject (remove) the wafer in the carrying
process.
[0026] Furthermore, the wafer separation apparatus or the wafer
separation and transfer apparatus according to the invention is
characterized by including a moving unit configured to move the
nozzle or the cassette support along a direction of arranging the
wafers.
[0027] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
it is possible to uniformly issue micro bubbles toward each space
between the wafers.
[0028] In addition, the wafer separation apparatus or the wafer
separation and transfer apparatus according to the invention is
characterized by including a cover configured to cover five sides
except the underside of the cassette support as the cassette
support is immersed in the inside of the liquid bath.
[0029] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
it is possible to facilitate causing micro bubbles to enter each
space between the wafers.
[0030] The wafer separation apparatus or the wafer separation and
transfer apparatus according to the invention is characterized in
that the micro bubble generator causes the nozzle to issue
negatively charged micro bubbles.
[0031] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
it is possible to cause micro bubbles to enter the space between
the wafers so that the micro bubbles are brought into the space, if
the space between the wafers after sliced with a wire-saw is
positively charged.
[0032] The wafer separation apparatus or the wafer separation and
transfer apparatus according to the invention is characterized in
that the micro bubble generator causes the nozzle to issue a micro
bubble having a diameter equal to a width of a groove or less, the
groove being cut with a wire-saw used in slicing a silicon ingot
into single wafers.
[0033] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
typically, the groove width of a groove formed between the wafers
is the wire diameter of the wire-saw or more. Thus, it is made
possible to cause micro bubbles to enter the space between the
wafers by issuing micro bubbles having an air bubble diameter equal
to this groove width or less.
[0034] The wafer separation apparatus or the wafer separation and
transfer apparatus according to the invention is characterized in
that the micro bubble generator causes the nozzle to issue a micro
bubble having a diameter equal to a wire diameter of a wire-saw or
less, the wire-saw being used in slicing a silicon ingot into
single wafers.
[0035] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
typically, the groove width of a groove formed between the wafers
is the wire diameter of the wire-saw or more. Thus, it is made
possible to more reliably cause micro bubbles to enter the space
between the wafers by issuing micro bubbles having the air bubble
diameter equal to the wire diameter or less, based on the wire
diameter.
[0036] The wafer separation apparatus or the wafer separation and
transfer apparatus according to the invention is characterized in
that the micro bubble generator causes the nozzle to issue a micro
bubble having a diameter of 100 .mu.m or less.
[0037] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
the wire diameter of a wire used for the wire-saw ranges from 100
to 150 .mu.m. Thus, it is made possible to reliably cause micro
bubbles to enter the space between the wafers without providing
special design changes or the like by generating micro bubbles
having the air bubble diameter, based on the minimum diameter of
the wire.
[0038] The wafer separation apparatus or the wafer separation and
transfer apparatus according to the invention is characterized in
that the micro bubble generator causes the nozzle to issue a micro
bubble having a diameter of 20 .mu.m or less on average.
[0039] In accordance with the wafer separation apparatus or the
wafer separation and transfer apparatus according to the invention,
it is possible to increase the volume of an air layer for
implementing more reliable separation by increasing the number of
micro bubbles that enter the space between the wafers in a large
number. In addition, because a large or small error occurs in the
air bubble diameter of actual micro bubbles to some extent, it is
possible that the mean value is determined to be the criterion of
the diameter of air bubbles to be generated for defining the air
bubble diameter.
[0040] The wafer separation and transfer apparatus according to the
invention is characterized in that the cassette vertically
accommodates therein a large number of the single wafers in
intimate contact with each other so that a running direction of the
wire-saw used in slicing a silicon ingot into single wafers is the
same as wafer unloading and transfer directions of the unloading
member and the carrier unit.
[0041] In accordance with the wafer separation and transfer
apparatus according to the invention, the direction of cuts formed
along the wire running direction in slicing the ingot using the
wire-saw and the wafer transfer direction are made the same. Thus,
it is possible to suppress the occurrence of scratches crossing the
wire carrying direction in carrying the wafers.
[0042] The wafer separation and transfer apparatus according to the
invention is characterized in that the rotating unit supports the
cassette support so that a top edge of the wafers comes close to a
vertical inner wall surface of the liquid bath in the state in
which the wafers are vertically arranged and accommodated in the
cassette when the cassette support is erected.
[0043] In accordance with the wafer separation and transfer
apparatus according to the invention, it is possible to eliminate
the event that micro bubbles entering the space between the wafers
cause the individual wafers to move unexpectedly when the cassette
support is erected to horizontally arrange the wafers.
[0044] A wafer separation method according to the present invention
is characterized by including: an accommodating step of vertically
accommodating a large number of single wafers in a cassette in
intimate contact with each other, the cassette being at least
vertically opened; a mounting and supporting step of mounting and
supporting the cassette on a cassette support at least vertically
opened; a lowering step of lowering the cassette support integrally
with the cassette using a hoisting unit and immersing the wafers
vertically arranged in a liquid in an inside of the liquid bath;
and a micro bubble issuing step of issuing micro bubbles generated
in a micro bubble generator from an underside of the cassette
support toward the wafers vertically arranged and causing the micro
bubbles to enter and stay in a large number of the individual
wafers.
[0045] In accordance with the wafer separation method according to
the present invention, it is possible to improve wafer separation
performance, and it is possible to suppress the occurrence of
breakage or the like of wafers, while the apparatus is an
inexpensive, small-sized apparatus.
[0046] A wafer separation and transfer method according to the
present invention is characterized by including: an accommodating
step of vertically accommodating a large number of single wafers in
a cassette in intimate contact with each other, the cassette being
at least vertically opened; amounting and supporting step of
mounting and supporting the cassette on a cassette support at least
vertically opened; a lowering step of lowering the cassette support
integrally with the cassette using a hoisting unit and immersing
the wafers vertically arranged in a liquid in an inside of the
liquid bath; a micro bubble issuing step of issuing micro bubbles
generated in a micro bubble generator from an underside of the
cassette support toward the wafers vertically arranged and causing
the micro bubbles to enter and stay in each space between a large
number of the wafers; a rotating step of rotating the cassette
support integrally with the cassette to horizontally arrange a
large number of the wafers using a rotating unit, while the micro
bubbles enter and stay in each space between a large number of the
wafers; a hoisting step of hoisting the cassette support integrally
with the cassette as the wafers are horizontally arranged using the
hoisting unit and lifting a topmost wafer above at least a liquid
level of the liquid bath; an unloading step of unloading the
topmost wafer lifted above the liquid level; and a carrying step of
carrying the unloaded wafer.
[0047] In accordance with the wafer separation and transfer method
according to the present invention, it is possible to improve wafer
separation performance in separation and transfer, and it is
possible to suppress the occurrence of breakage or the like of
wafers in separation and transfer, while the apparatus is an
inexpensive, small-sized apparatus.
[0048] A wafer separation and transfer method according to the
present invention is characterized by including: an accommodating
step of vertically accommodating a large number of single wafers in
a cassette in intimate contact with each other after removal of the
wafers, the cassette being at least vertically opened; a mounting
and supporting step of mounting and supporting the cassette on a
cassette support at least vertically opened; a pre-washing step of
lowering the cassette support integrally with the cassette using a
hoisting unit and pre-washing the wafers vertically arranged; an
unloading and carrying step of unloading and carrying the cassette
after pre-washed; a lowering step of immersing the carried cassette
in a liquid in an inside of a liquid bath; a micro bubble issuing
step of issuing micro bubbles generated in a micro bubble generator
from an underside of the cassette support toward the wafers
vertically arranged and causing the micro bubbles to enter and stay
in each space between a large number of the wafers; a rotating step
of rotating the cassette support integrally with the cassette to
horizontally arrange a large number of the wafers using a rotating
unit, while the micro bubbles enter and stay in each space between
a large number of the wafers; a hoisting step of hoisting the
cassette support integrally with the cassette as the wafers are
horizontally arranged using the hoisting unit and lifting a topmost
wafer above at least a liquid level of the liquid bath; an
unloading step of unloading the topmost wafer lifted above the
liquid level; and a carrying step of carrying the unloaded
wafer.
[0049] In accordance with the wafer separation and transfer method
according to the present invention, it is possible to pre-wash
sliced wafers and also separate and carry the sliced wafers, and it
is also possible to completely automate the operation process steps
from pre-washing to separation and transfer.
[0050] A solar cell wafer separation and transfer method according
to the present invention is characterized by including: a slicing
step of slicing a silicon ingot integrally with a support plate
into a large number of wafers; a removing step of removing the
sliced silicon ingot from the support plate for single wafers; an
accommodating step of vertically accommodating a large number of
the single wafers in a cassette in intimate contact with each other
after removal of the wafers, the cassette being at least vertically
opened; a mounting and supporting step of mounting and supporting
the cassette on a cassette support at least vertically opened; a
lowering step of lowering the cassette support integrally with the
cassette using a hoisting unit and immersing the wafers vertically
arranged in a liquid in an inside of the liquid bath; a micro
bubble issuing step of issuing micro bubbles generated in a micro
bubble generator from an underside of the cassette support toward
the wafers vertically arranged and causing the micro bubbles to
enter and stay in each space between a large number of the wafers;
a rotating step of rotating the cassette support integrally with
the cassette to horizontally arrange a large number of the wafers
using a rotating unit, while the micro bubbles enter and stay in
each space between a large number of the wafers; a hoisting step of
hoisting the cassette support integrally with the cassette as the
wafers are horizontally arranged using the hoisting unit and
lifting a topmost wafer above at least a liquid level of the liquid
bath; an unloading step of unloading the topmost wafer lifted above
the liquid level; a carrying step of carrying the unloaded wafer;
and a transfer step of transferring the carried wafer to a solar
cell fabrication apparatus.
[0051] In accordance with the solar cell wafer separation and
transfer method according to the present invention, it is possible
to improve wafer separation performance in separation and transfer
of solar cell wafers, and it is possible to suppress the occurrence
of breakage or the like of wafers in separation and transfer, while
the apparatus is an inexpensive, small-sized apparatus. In
addition, it is also possible that after the carried wafer is
collected automatically collected in a wafer collection box in the
carrying step and the wafer collection box after collected is
automatically carried to the subsequent step using a multi-robot
arm.
[0052] The solar cell wafer separation and transfer method
according to the invention is characterized in that in the transfer
step, the wafer is transferred to a chemical etching apparatus for
texture treatment to fabricate a p-type wafer or n-type wafer.
[0053] The wafer separation method, the wafer separation and
transfer method, or the solar cell wafer separation and transfer
method according to the invention is characterized in that in the
micro bubble issuing step, the nozzle or the cassette support is
moved along a direction of arranging the wafers.
[0054] The wafer separation method, the wafer separation and
transfer method, or the solar cell wafer separation and transfer
method according to the invention is characterized in that before
starting the micro bubble issuing step, five sides except the
underside of the cassette support is covered with a cover as the
cassette support is immersed in the inside of the liquid bath.
Effect of the Invention
[0055] The wafer separation apparatus according to the present
invention can improve wafer separation performance in separation
and transfer and can suppress the occurrence of breakage or the
like of wafers in separation and transfer, while the apparatus is
an inexpensive, small-sized apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] FIG. 1 is a cross sectional view depicting a wafer
separation and transfer apparatus in the front side direction,
including a wafer separation apparatus according to an embodiment
of the present invention in which wafers are set;
[0057] FIG. 2 is a cross sectional view depicting the wafer
separation and transfer apparatus in the front side direction,
including the wafer separation apparatus according to an embodiment
of the present invention in which air bubbles are issued (wafer
separation state);
[0058] FIG. 3 shows the wafer separation apparatus according to an
embodiment of the present invention, (A) is an enlarged cross
sectional view depicting the essential part showing the
relationship between wafers and air bubbles, and (B) is an
illustration depicting an air bubble;
[0059] FIG. 4 is a cross sectional view depicting the wafer
separation and transfer apparatus in the side direction, including
the wafer separation apparatus according to an embodiment of the
present invention in which wafers are vertically arranged;
[0060] FIG. 5 is an illustration depicting the wafer separation and
transfer apparatus, including the wafer separation apparatus
according to an embodiment of the present invention in which wafers
are horizontally arranged;
[0061] FIG. 6 is an illustration depicting the wafer separation and
transfer apparatus, including the wafer separation apparatus
according to an embodiment of the present invention as a wafer is
carried;
[0062] FIG. 7 is an illustration depicting the wafer separation and
transfer apparatus according to an embodiment of the present
invention;
[0063] FIG. 8 is a flowchart depicting an operation routine from
wafer slicing to separation and transfer for the wafer separation
apparatus according to an embodiment of the present invention;
[0064] FIG. 9 is a flowchart depicting a transfer operation routine
for the wafer separation apparatus according to an embodiment of
the present invention;
[0065] FIG. 10 is an illustration of the apparatus layout of the
wafer separation apparatus according to an embodiment of the
present invention, including pre-washing;
[0066] FIG. 11 is an illustration depicting the shaping process of
a silicon ingot;
[0067] FIG. 12 is an illustration depicting a silicon ingot being
sliced; and
[0068] FIG. 13 is an illustration depicting a silicon ingot before
separated (batch).
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0069] 1 Silicon ingot [0070] 1a Silicon waste material [0071] 1b
Silicon waste material [0072] 2 Silicon block [0073] 3 Wire-saw
[0074] 4 Wire [0075] 5 Wire guide [0076] 6 Wire feed pulley [0077]
7 Wire winding pulley [0078] 8 Wire winding device [0079] 9 Mount
member [0080] 10 Support plate [0081] 11 Safer separation and
transfer apparatus [0082] 12 Cassette [0083] 12a Lower opening
[0084] 13 Cassette support [0085] 13a Lower opening [0086] 14
Hoisting unit [0087] 15 Rotating unit [0088] 16 Liquid bath [0089]
17 Nozzle [0090] 18 Micro bubble generator [0091] 19 Unloading
member [0092] 20 Carrier unit [0093] 21 Moving unit [0094] 22 Cover
[0095] 23 Shaft [0096] 24 Intermediate support [0097] 25 Guide rail
[0098] 26 Guide plate [0099] 27 Fixed shaft [0100] 28 Fixed base
[0101] 29 Support base [0102] 29a Lower plate [0103] 29b Upper
plate [0104] 29c Vertical plate [0105] 30 Shaft support part [0106]
31 Drive motor [0107] 32 Drive pulley [0108] 33 Rotating shaft
[0109] 34 Idler pulley [0110] 35 Endless belt [0111] 36 Rotating
arm [0112] 37 Roller member [0113] 38 Transfer support plate [0114]
39 Defect determining device [0115] 40 Transfer belt conveyor
[0116] 41 Diverging device [0117] 42 Collecting device [0118] 43
Cabinet [0119] 44 Servo motor [0120] 45 Drive pulley [0121] 46
Idler pulley [0122] 47 Belt [0123] 48 Ball screw [0124] 49 Hoisting
and lowering member [0125] 50 Wafer collection box [0126] 51 Guide
rail [0127] 52 Guide projection [0128] 53 Coupling part [0129] 61
Pre-washing bath (pre-washing device) [0130] 62 Conveying
device
BEST MODE FOR CARRYING OUT THE INVENTION
[0131] Next, a wafer separation apparatus according to an
embodiment of the present invention will be described with
reference to the drawings. In addition, an embodiment shown below
is a preferable, specific example of a wafer separation apparatus
according to the present invention. For example, in some cases,
technically preferable limitations are variously placed such as
limitations on numeric values, materials, etc. However, the
technical scope of the present invention is not limited to these
modes unless otherwise noted that the present invention is limited
particularly.
[0132] First, for describing the wafer separation apparatus
according to an embodiment of the present invention, an exemplary
fabrication process before the separation of silicon single crystal
wafers will be described with reference to FIGS. 11 to 13.
[0133] More specifically, as shown in FIG. 11, for the silicon
single crystal wafer, a nearly cylindrical silicon ingot 1 (see the
upper part in FIG. 11) integrally has a silicon waste material in a
nearly conical shape at the left and right end (the upper and lower
end in growing the ingot), which was produced by the Czochralski
method (pulling method) or the like, silicon waste materials 1a and
1b are cut off, and the ingot 1 is cut out in a suitable size
(length) as necessary (see in the middle part in FIG. 11). A
silicon block 2 in a prism having a nearly rectangular cross
section (each corner is beveled in some cases) is then obtained
from a cylinder using a band saw or the like (see the lower part in
FIG. 11).
[0134] More specifically, in fabricating silicon wafers for solar
cells, the cross sectional shape of the silicon block 2 is
preferably in a rectangle or nearly rectangle, and one cut out of
the silicon ingot 1 is preferable.
[0135] Subsequently, as shown in FIG. 12, the silicon block 2 is
sliced into a large number of wafers using a wire-saw 3.
[0136] This wire-saw slices the silicon block 2 into a large number
of wafers, in which a plurality of wire guides 5 (for example,
three guides) with a cutting wire 4 spirally wound thereon along a
plurality of grooves are rotated to run the wire 4 while slurry
that is a mixed solution of oil and abrasive grains is discharged
from a slurry nozzle, not shown, and cutting feed is provided
between the wire 4 and the silicon block 2 in this state.
[0137] In addition, in FIG. 12, 6 denotes a wire feed pulley, 7
denotes a wire winding pulley, and 8 denotes a wire winding
device.
[0138] Moreover, in slicing the silicon block 2 using the wire 4,
for example, a support plate 10 made of glass or the like is
mounted on a mount member 9, which is made of stainless steel or
the like and provided on a block hoisting support device, not
shown, and the top side of the silicon block 2 is bonded and fixed
to the underside of the support plate 10 through an adhesive, not
shown. Furthermore, in slicing with the wire 4, cutting grooves are
partially provided to the lower part of the support plate 10 in
order to facilitate the separation of the individual sliced wafers
into single wafers.
[0139] After that, the support plate 10 is demounted from the mount
member 9, and then the silicon block 2 with cutting grooves is
obtained, which is a cylindrical pack of wafers attached to the
support plate 10 as shown in FIG. 13.
[0140] This silicon block 2 is pre-washed in a pre-washing device,
not shown, for removing slurry, cutting dust, or the like as the
cylindrical pack of wafers is attached to the support plate 10, and
then the support plate 10 is removed from the silicon block 2 by
secondary washing for single wafers.
[0141] In the following, transfer performed by the wafer separation
apparatus according to an embodiment of the present invention will
be described with reference to FIGS. 1 to 7.
[0142] FIG. 1 is a cross sectional view depicting a wafer
separation and transfer apparatus in the front side direction,
including the wafer separation apparatus according to an embodiment
of the present invention in which wafers are set. FIG. 2 is across
sectional view depicting the wafer separation and transfer
apparatus in the front side direction, including the wafer
separation apparatus according to an embodiment of the present
invention in which air bubbles are issued (wafer separation state).
FIG. 3 shows the wafer separation apparatus according to an
embodiment of the present invention; FIG. 3(A) is an enlarged cross
sectional view depicting the essential part showing the
relationship between wafers and air bubbles, and FIG. 3(B) is an
illustration depicting an air bubble. FIG. 4 is a cross sectional
view depicting the wafer separation and transfer apparatus in the
side direction, including the wafer separation apparatus according
to an embodiment of the present invention in which wafers are
vertically arranged. FIG. 5 is an illustration depicting the wafer
separation and transfer apparatus, including the wafer separation
apparatus according to an embodiment of the present invention in
which wafers are horizontally arranged. FIG. 6 is an illustration
depicting the wafer separation and transfer apparatus, including
the wafer separation apparatus according to an embodiment of the
present invention as a wafer is carried. FIG. 7 is an illustration
depicting the wafer separation and transfer apparatus according to
an embodiment of the present invention. FIG. 8 is a flowchart
depicting an operation routine from wafer slicing to separation and
transfer for the wafer separation apparatus according to an
embodiment of the present invention.
[0143] As shown in FIGS. 1 to 5, a wafer separation and transfer
apparatus 11 including the wafer separation apparatus according to
an embodiment of the present invention has a cassette 12 that
vertically accommodates a large number of single wafers W in
intimate contact with each other and is at least vertically opened,
a cassette support 13 that removably support the cassette 12 and is
at least vertically opened, a hoisting unit 14 that hoists and
lowers the cassette support 13 integrally with the cassette 12, a
rotating unit 15 provided on the hoisting unit 14 for rotating the
cassette support 13 integrally with the cassette 12 so as to switch
the wafers W accommodated in the cassette 12 between the states in
which they are vertically arranged and they are horizontally
arranged, a liquid bath 16 that accommodates a liquid thereinside
into which the cassette support 13 is immersed integrally with the
cassette 12 when the hoisting unit 14 descends, a nozzle 17
provided in the liquid bath 16 for issuing micro bubbles from the
underside of the cassette support 13 toward a large number of the
wafers W, a micro bubble generator 18 that generates micro bubbles
to be issued from the nozzle 17, an unloading member 19 that
unloads a topmost one out of the wafers W horizontally arranged and
hoisted from the inside of the liquid bath 16, and a carrier unit
20 that carries the topmost wafer W unloaded by the unloading
member 19.
[0144] According to the wafer separation and transfer apparatus 11
thus configured, it is possible to improve separation performance
of the wafers W in separation and transfer and it is possible to
suppress the occurrence of breakage or the like of the wafers W in
separation and transfer, while the apparatus is an inexpensive,
small-sized apparatus.
[0145] At this time, the wafer separation and transfer apparatus 11
includes a moving unit 21 that moves the nozzle 17 or the cassette
support 13 along the direction of arranging the wafers W, so that
it is possible to cause micro bubbles to be uniformly issued toward
the space between the individual wafers W.
[0146] Moreover, a cover 22 is provided to cover five sides except
the underside of the cassette support 13, which is immersed in the
liquid bath 16, so that it is possible to facilitate causing micro
bubbles to enter the space between the individual wafers W.
[0147] Furthermore, the micro bubble generator 18 causes the nozzle
17 to issue negatively charged micro bubbles, so that it is
possible to cause micro bubbles to enter the space between the
wafers W so that the micro bubbles are brought into the space
between the wafers W, if the space between the wafers W, which are
sliced with the wire-saw 3, is positively charged.
[0148] In addition, preferably, the micro bubble generator 18
causes the nozzle 17 to issue a micro bubble having a diameter
equal to a groove width or less when the ingot is sliced with the
wire-saw 3. More preferably, it causes the nozzle 17 to issue a
micro bubble having a diameter equal to or less than the wire
diameter of the wire 4 used in the wire-saw 3, which is used in
slicing the silicon ingot 1 into single wafers. Further more
preferably, it causes the nozzle 17 to issue a micro bubble having
a diameter of 100 .mu.m or less. The best is that it causes the
nozzle 17 to issue a micro bubble having a diameter of 20 .mu.m or
less on average.
[0149] In addition, preferably, the cassette 12 vertically
accommodates a large number of the single wafers W in intimate
contact with each other so that the running direction of the
wire-saw 3 used in slicing the silicon ingot 1 into single wafers
is the same as the directions of unloading and carrying the wafer W
with the unloading member 19 and the carrier unit 20.
[0150] In the following, the specific configuration of the wafer
separation and transfer apparatus 11 according to the present
invention will be described.
[0151] The cassette 12 is not limited in shapes, materials, or the
like as the strength is secured particularly, as long as the
cassette 12 is capable of accommodating a large number of the
wafers W and is formed with a lower opening 12a for passing micro
bubbles issued from the nozzle 17 therethrough. In addition, in
this embodiment, the cassette 12 is designed in which the cassette
12 is also opened upward so that the cassette 12 can accommodate
the wafers W and the height is lower than the height of the wafers
W (when they are vertically arranged) so that the unloading member
19 can contact with a topmost wafer W horizontally arranged in
unloading the wafer W, described later.
[0152] The cassette support 13 is not limited in shapes, materials,
or the like as the strength is secured particularly, as along as
the cassette support 13 is capable of attaching, detaching, and
supporting the cassette 12 thereon and is formed with a lower
opening 13a for passing micro bubbles issued from the nozzle 17
therethrough. In addition, in this embodiment, the cassette support
13 is designed in which the cassette support 13 is also opened
upward so that the cassette support 13 can accommodate the cassette
12 and the height is lower than the height of the wafers W (when
they are vertically arranged) so that the unloading member 19 can
contact with a topmost wafer W horizontally arranged in unloading
the wafer W, described later.
[0153] The hoisting unit 14 includes a shaft 23 that is extended by
drive of a hoisting and lowering drive unit, not shown, (for
example, a solenoid), an intermediate support 24 fixed to the top
end of the shaft 23, a guide rail 25 vertically extended and fixed
to the side wall of the liquid bath 16, a guide plate 26 provided
on the intermediate support 24 and guided by the guide rail 25, a
fixed shaft 27 erected from the intermediate support 24, a fixed
base 28 in a crank shape in the cross section fixed to the top end
of the fixed shaft 27, a support base 29 in a crank shape in the
cross section fixed to the fixed base 28, and a shaft support part
30 fixed to a lower plate 29a of the support base 29.
[0154] In addition, because the guide rail 25 and the guide plate
26 support the rotating unit 15 and the cassette 12 with the fixed
shaft 27 as one side is opened, they are designed to slide at the
positions in consideration of the weight balance (in the lateral
direction of FIG. 1).
[0155] In addition, the support base 29 integrally includes an
upper plate 29b fixed to the top side of the fixed base 28 and
having the tip end protruded in the inside of the liquid bath 16, a
vertical plate 29c extended downwards from the tip end of the upper
plate 29b, and the horizontal lower plate 29a bent at a right angle
from the lower end of the vertical plate 29c toward the inner side
of the liquid bath 16. The support base 29 is formed of these
plates 29a, 29b, and 29c in a nearly crank shape in the cross
section.
[0156] The rotating unit 15 includes a drive motor 31 fixed to the
upper plate 29b and having the output shaft extended toward the
inside of the liquid bath 16, a drive pulley 32 provided on the
drive motor 31, a rotating shaft 33 that penetrates through the
shaft support part 30, an idler pulley 34 provided on one end of
the rotating shaft 33, an endless belt 35 rotatably and movably
extended between the pulleys 32 and 34, and a rotating arm 36
provided on the other end of the rotating shaft 33. The cassette
support 13 is fixed to this rotating arm 35. Moreover, the drive of
the drive motor 31 causes the rotating arm 35 to turn for rotating
the cassette 12 integrally with the cassette support 13. As shown
in FIG. 3, the individual wafers W accommodated in the cassette 12
are vertically arranged when the cassette support 13 is laid (in
the horizontal state), and as shown in FIG. 4, the wafers W
accommodated in the cassette 12 are horizontally arranged when the
cassette support 13 is erected (in the vertical state).
[0157] Furthermore, the rotating arm 35 is designed to come close
to the position at which the top edge of the wafers W accommodated
in the cassette 12 (when vertically arranged) is brought into
nearly contact with the inner wall surface of the liquid bath 16
when the rotating arm 35 is erected. In addition, when the rotating
arm 35 is brought close to the position at which the top edge of
the wafers W (when vertically arranged) is brought into nearly
contact with the inner wall surface of the liquid bath 16 as the
rotating arm 35 is erected, it is possible to eliminate the event
that micro bubbles B entering the space between the wafers W,
described later, cause the individual wafers W to move
unexpectedly.
[0158] The liquid bath 16 accommodates a liquid such as pure water
thereinside, and has such depth that the hoisting unit 14 lowers
the wafers W accommodated in the cassette 12 to be completely
immersed. Moreover, in this embodiment, the depth of the liquid
bath 16 is designed to have such depth (at least the liquid level)
that the wafers W are completely immersed even in the state in
which the hoisting unit 14 erects the cassette support 13 as the
hoisting unit 14 is positioned at the bottom dead center.
Furthermore, it is possible to suitably select the liquid
accommodated in the liquid bath 16 except volatility, in
consideration that it is necessary to cause micro bubbles,
described later, to stay in the space between the wafers W for a
while. For example, in the case of combining secondary washing, it
is possible to use a secondary washing fluid or the like.
[0159] The nozzle 17 is provided near the deepest part of the
liquid bath 16. The number or the like thereof is not limited
particularly as long as it can issue micro bubbles generated in the
micro bubble generator 18.
[0160] The micro bubble generator 18 includes a pump, mixer, both
are not shown, or the like, for example, for which a publicly known
one is used, in which pressure is set to change and adjust the air
bubble diameter of micro bubbles to be generated. In addition, in
this embodiment, the air bubble diameter is 100 .mu.m or less.
Strictly speaking, as shown in FIG. 6(A), the structure or the like
is not limited particularly as long as it can generate so-called
nanobubbles, which the average air bubble diameter of micro bubbles
B entering the space between the wafers W is around 20 .mu.m.
[0161] At this time, in the micro bubble generator 18, the inner
side of the air bubble is negatively (-) charged, as shown in FIG.
6(B).
[0162] Thus, because slurry or the like, which is removed in
pre-washing or secondary washing, for example, is positively
charged, it is possible to efficiently cause micro bubbles to enter
the space between the wafers W by the effect of drawing the
negatively charged micro bubbles, as it is considered that the
space between the wafer W or the like is positively charged,
including the case where this slurry remains after secondary
washing.
[0163] For the unloading member 19, a roller member or the like is
used, which is rotated by drive of a drive motor, not shown, or the
like (in the counterclockwise direction in FIG. 1), and for the
material or the like, there is used such one that has elasticity
and a relatively high frictional resistance (for example,
urethane). In addition, the unloading member 19 is formed of a
single roller member in this embodiment. However, it is possible to
design the position and number of the unloading member 19 in
consideration of the transfer range of the wafer W.
[0164] As shown in FIG. 7, the carrier unit 20 includes a vertical
pair of roller members 37 that nip and carry the wafer W by
individually turning in the reverse direction using the drive motor
also serving to rotate the unloading member 19 or using a separate
device, a transfer support plate 38 provided next to the roller
members 37 on the downstream side of the transfer direction, a
defect determining device 39 provided above the transfer support
plate 38, a plurality of transfer belt conveyors 40 provided next
to the transfer support plate 38 on the downstream side of the
transfer direction, a diverging device 41 that discards and
collects a wafer W determined that the wafer W has a defect by the
defect determining device 39 at any positions on the transfer belt
conveyor 40, and a collecting device 42 that collects a wafer W
with no defect. Moreover, for the transfer support plate 38 and the
transfer belt conveyor 40, a material with elasticity and a
relatively high frictional resistance is used (for example,
urethane). Furthermore, the diverging device 41 temporarily breaks
the transfer path as a part of the transfer belt conveyor 40 is
tilted, for example, (in the state depicted by a chain
double-dashed line in FIG. 8), and discards and collects wafers W
at the position of breaking the path on the downstream side of the
transfer direction. At this time, the wafers W discarded and
collected are recycled.
[0165] The defect determining device 39 determines whether cracks
(cracking, chipping, or the like) occur by imaging processes using
a CCD camera.
[0166] The collecting device 42 includes a cabinet 43, a servo
motor 44 provided on the cabinet 43, a drive pulley 45 provided on
the output shaft of the servo motor 44, an idler pulley 46
rotatably supported on the cabinet 43, a belt 47 rotatably and
movably provided on the pulleys 45 and 46, a ball screw 48 that
penetrates through the idler pulley 46 and is vertically displaced
by the rotation of the idler pulley 46, a hoisting and lowering
member 49 coupled to one end of the ball screw 48, and a wafer
collection box 50 removably mounted on the hoisting and lowering
member 49.
[0167] The front side of the wafer collection box 50 is opened, and
a partition such as a slit, not shown, is provided so as to
accommodate each one of the wafers W after washed as they are
separated from each other. Moreover, on the rear side of the
hoisting and lowering member 49, a guide projection 52 is provided
to engage with the guide rail 51 installed on the cabinet 43.
Furthermore, on the topside of the hoisting and lowering member 49,
a coupling part 53 is provided, to which one end of the ball screw
48 is rotatably coupled.
[0168] With this configuration, the wafers W carried on the
transfer belt conveyors 40 are collected and accommodated one by
one from above the wafer collection box 50 as they are separated
into single wafers, and the wafers W are collected and accommodated
in each partition while the wafer collection box 50 is sequentially
displaced upward by the inching drive of the servo motor 44.
[0169] At this time, preferably, the downstream end of the transfer
belt conveyor 40 placed on the most downstream side in the wafer
transfer direction faces the inside of the wafer collection box
50.
[0170] Moreover, the drive pulley 45 and the idler pulley 46 are
adjusted as similar to the adjustment of the gear ratio by changing
the diameter. Furthermore, a solenoid or the like may be used for
the servomotor 44, the idler pulley 46, the belt 47, and the ball
screw 48.
[0171] The moving unit 21 horizontally moves the nozzle 17 along
the direction of arranging the wafers W, which moves it at a rate
of 5.0 mm/sec, for example. In addition, it is also possible that
this moving unit 21 horizontally moves the cassette 12 along the
direction of arranging the wafers W instead of moving the nozzle
17.
[0172] The cover 22 covers five sides of the cassette support 13
except the underside with less clearance, which contains the micro
bubbles issued from the nozzle 17 inside the cover 22 to facilitate
causing micro bubbles to enter the space between the individual
wafers W. Moreover, materials, shapes, or the like of the cover 22
are not limited particularly. Furthermore, the cover 22 is removed
while the hoisting unit 14 is hoisting and lowering the cassette
12, or in the state in which the cassette support 13 is rotated and
erected.
[0173] In the above-mentioned configuration, the wafers W are
subjected to the following steps. A slicing step of slicing the
silicon ingot 1 integrally with the support plate 10 into a large
number of wafers (Step S1), a removing step of removing the sliced
silicon ingot 1 from the support plate 10 for single wafers (Step
S2), an accommodating step of vertically accommodating a large
number of the removed single wafers W in the cassette 12 in
intimate contact with each other, the cassette 12 being at least
vertically opened (Step S3), a mounting and supporting step of
mounting and supporting the cassette 12 on the cassette support 13
that is at least vertically opened (Step S4), a lowering step of
lowering the cassette support 13 integrally with the cassette 12
using the hoisting unit 14 and immersing the wafers W vertically
arranged in a liquid in the inside of the liquid bath 16 (Step S5),
a micro bubble issuing step of issuing micro bubbles generated in
the micro bubble generator 18 from the nozzle 17 from the underside
of the cassette support 13 toward the wafers W vertically arranged
and causing the micro bubbles to enter and stay in the space
between a large number of the wafers W (Step S6), a rotating step
of rotating the cassette support 13 integrally with the cassette 12
to horizontally arrange a large number of the wafers W using the
rotating unit 15 while the micro bubbles enter and stay in the
space between a large number of the wafers W (Step S7), a hoisting
step of hoisting the cassette support 13 integrally with the
cassette 12 as the wafers W are horizontally arranged using the
hoisting unit 14 and lifting a topmost wafer W above at least the
liquid level of the liquid bath 16 (Step S8), an unloading step of
unloading the topmost wafer W lifted above the liquid level (Step
S9), a carrying step of carrying the unloaded wafer W (Step S10),
and a transfer step of transferring the carried wafer W to a solar
cell fabrication apparatus (Step S 11). Through these steps, it is
possible to transfer the wafers W as solar cell wafers to
fabrication processes, such as the transfer of the wafers W to a
chemical etching apparatus for texture treatment to fabricate
p-type wafers W or n-type wafers W, for example.
[0174] More specifically, after the silicon ingot 1 is sliced using
the wire-saw 3 in Step S1, the sliced silicon ingot 1, which is
still supported by the support 10, is passed from the wire-saw 3
through a publicly known pre-washing device and secondary washing
device for removing slurry or the like as well as for removing the
support 10, and then the wafers W become single wafers (Step
S2).
[0175] For the individual single wafers W, a large number of the
wafers W are accommodated in the cassette 12 in intimate contact
with each other, with the use of the cassette 12 or the like, which
has been so far used in manual operations of washing, removing, and
separation (Step S3), and the cassette 12 is mounted and supported
on the cassette support 13 as the cassette 12 is carried in the
wafer separation and transfer apparatus 11 depending on factories
or the like (Step S4).
[0176] After that, the solenoid or the like is driven to lower the
cassette support 13 into the liquid bath 16 having the liquid in
advance accommodated thereinside to the bottom dead center at which
the wafers W are completely immersed (Step S5).
[0177] Subsequently, the micro bubble generator 18 is driven to
cause micro bubbles having an air bubble diameter of 20 .mu.m on
average to be issued from the nozzle 17, and the micro bubbles
(nanobubbles) B having an average air bubble diameter of 20 .mu.m
are caused to enter the space between the individual wafers W while
the nozzle 17 is moved at a predetermined rate (Step S6).
[0178] Moreover, after the micro bubbles B enter all the spaces
between the wafers W, the drive motor 31 is driven to turn the
rotating shaft 33 by rotating and moving the endless belt 35, and
the cassette support 13 is erected in association with the rotation
of the rotating arm 36 (Step S7).
[0179] After that, the cassette support 13 is hoisted to a
predetermined unloading position at which the topmost wafer W is
positioned above the top edge of the liquid bath 16, and the
cassette support 13 is stopped at this predetermined unloading
position (Step S8).
[0180] The unloading member 19 is then contacted with the topmost
wafer W, and the unloading member 19 is rotated to unload the
topmost wafer W (Step S9). The topmost wafer W is nipped and
carried by the carrier unit 20 (Step S10), and the topmost wafer W
is transferred to the collecting device 42 (Step S11).
[0181] Moreover, these Steps S9 to S11 are also performed to a
topmost wafer W after the subsequent stage one by one, and the
hoisting unit 14 hoists the lower set support 13 as necessary, (for
example, as for three wafer each).
[0182] Furthermore, in the transfer process in Step 11, a defect on
the wafer W is determined by the defect determining device 39 (Step
S12). If a defect occurs, a faulty wafer W is diverged (ejected) by
the diverging device 41 (Step S13), and wafers W with no defect are
in turn collected in the wafer collection box 50 by the collecting
device 42 (Step S14).
[0183] Moreover, in this embodiment, the wafers W, which are sliced
into a large number of wafers with the wire-saw 3, are directly
separated and carried. However, as shown in FIG. 10, such a
configuration is possible that a pre-washing bath (pre-washing
device) 61 is used as a device equivalent to the micro bubble
generator 18 shown in the present invention, in which the wafers W
accommodated in the cassette 12 passed from Step S1 through Step S3
are pre-washed, and they are then separated and carried through one
or more of conveying devices 62.
[0184] Furthermore, it is also possible that the wafers W after
collected in the wafer collection box 50 are automatically
transferred in the wafer collection box 50 as a whole using a
multi-robot arm, not shown, and they are transferred to a device
for the subsequent process step (final washing or mirror-like
finishing).
[0185] As described above, in accordance with the wafer separation
apparatus according to the present invention, the micro bubbles B
are caused to enter the space between a large number of the
individual wafers W, which are removed from the support 10, so that
it is possible to suppress sticking between the individual wafers W
and to efficiently perform the separating operation.
[0186] In addition, the micro bubbles B just enter the space
between the individual wafers W, thereby separating the wafers W
into single wafers. Thus, it is possible to suppress the occurrence
of breakage or the like caused by forced separation (for example, a
jet of pressure water or the like).
[0187] Now, in the above-mentioned embodiment, although explanation
is made in which the wafer separation apparatus according to the
present invention is adapted to the silicon single crystal wafer,
it is also possible to apply the apparatus to polysilicon
wafers.
[0188] At this time, for the polysilicon wafer, a rectangular
polysilicon ingot is cut into a rectangular polysilicon block using
a band saw or the like, for example, and the ingot is subjected to
the finishing process such as sizing, etching, or the like, and
then the ingot is sliced with the above-mentioned wire-saw or the
like.
INDUSTRIAL APPLICABILITY
[0189] As discussed above, according to the present invention, it
is possible to provide a wafer separation apparatus that can
improve wafer separation performance in separation and transfer and
can suppress the occurrence of breakage or the like of wafers in
separation and transfer while the apparatus is an inexpensive,
small-sized apparatus.
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