U.S. patent application number 09/184652 was filed with the patent office on 2002-01-17 for apparatus and method for automatically transferring wafers between wafer holders in a liquid environment.
Invention is credited to FUKABORI, HIROAKI, MUKAINO, YUKIO, SATO, MICHITO.
Application Number | 20020006324 09/184652 |
Document ID | / |
Family ID | 22677791 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020006324 |
Kind Code |
A1 |
SATO, MICHITO ; et
al. |
January 17, 2002 |
APPARATUS AND METHOD FOR AUTOMATICALLY TRANSFERRING WAFERS BETWEEN
WAFER HOLDERS IN A LIQUID ENVIRONMENT
Abstract
An apparatus for transferring wafers between wafer holders such
as wafer cassettes, etching drums and the like includes a tank for
containing a liquid transfer medium in which the wafers can be
transferred. The apparatus includes a wafer transfer unit that can
transfer a plurality of wafers such as semiconductor wafers between
wafer holders, and maintain the wafers in a desired relative
orientation during transfer. For example, the wafers can be
maintained in a parallel relationship. The apparatus can be used to
automatically transfer wafers to etching drums without
cross-indexing of the wafers and without manual handling of the
wafers.
Inventors: |
SATO, MICHITO; (VANCOUVER,
WA) ; FUKABORI, HIROAKI; (TAKASAKI-SHI, JP) ;
MUKAINO, YUKIO; (NISHISHIRAKAWA-GUN, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Family ID: |
22677791 |
Appl. No.: |
09/184652 |
Filed: |
November 3, 1998 |
Current U.S.
Class: |
414/416.12 ;
118/500; 134/902; 414/938 |
Current CPC
Class: |
Y10S 414/138 20130101;
Y10S 134/902 20130101; Y10S 414/14 20130101; H01L 21/67086
20130101 |
Class at
Publication: |
414/416.12 ;
414/938; 118/500; 134/902 |
International
Class: |
H01L 021/306 |
Claims
What is claimed is:
1. An apparatus for transferring wafers between wafer holders,
comprising: a transfer chamber containing a liquid; and a transfer
unit for transferring at least one wafer in the liquid from a first
wafer holder to a second wafer holder.
2. The apparatus of claim 1, further comprising: a first stand
disposed in the liquid in the transfer chamber; a first lift for
supporting the first wafer holder; a second stand disposed in the
liquid in the transfer chamber at a laterally spaced location from
the first stand; and a second lift disposed in the liquid in the
transfer chamber for supporting the second wafer holder; wherein
the transfer unit is operable to (i) move the first lift to
transfer in the liquid the at least one wafer from the first wafer
holder to the first stand, (ii) transfer in the liquid the at least
one wafer from the first stand to the second stand, and (iii) move
the second lift to transfer in the liquid the at least one wafer
from the second stand to the second wafer holder supported on the
second lift.
3. The apparatus of claim 2, wherein a plurality of wafers can be
(i) retained in a substantially parallel relationship during
transfer from the first wafer holder to the first stand, from the
first stand to the second stand, and from the second stand to the
second wafer holder, and (ii) supported on the second wafer holder
in the substantially parallel relationship.
4. The apparatus of claim 2, wherein the first wafer holder, first
stand, second stand and second wafer holder each include a
plurality of parallel grooves, and each groove of the first wafer
holder, first stand, second stand and second wafer holder are sized
to receive one said at least one wafer.
5. The apparatus of claim 2, wherein the transfer unit is operable
to automatically transfer the at least one wafer from the first
wafer holder to the first stand, from the first stand to the second
stand, and from the second stand to the second wafer holder, in the
liquid.
6. The apparatus of claim 2, wherein the first lift is sized to
support more than one first wafer holder, and each first wafer
holder is configured to support a plurality of wafers.
7. The apparatus of claim 1, wherein the materials forming the
apparatus are non-contaminating to the at least one wafer.
8. The apparatus of claim 2, wherein the transfer unit is operable
to (i) remove the second wafer holder containing the at least one
wafer from the liquid, (ii) move the second wafer holder to a
location spaced from the apparatus, (iii) transfer the second wafer
holder from the location back to the apparatus such that the second
wafer holder is supported on the second stand, (iv) transfer the at
least one wafer from the second wafer holder to the first stand,
and (v) move the first wafer holder to transfer the at least one
wafer from the first stand to the first wafer holder.
9. The apparatus of claim 1, wherein the first wafer holder is a
wafer cassette and the second wafer holder is an etching drum.
10. The apparatus of claim 2, wherein the transfer unit is operable
to (i) move the first lift in the transfer chamber such that the at
least one wafer is transferred from the first wafer holder to the
first stand, and (ii) move the second lift in the transfer chamber
such that the at least one wafer is transferred from the second
stand to the second wafer holder supported on the second lift.
11. An apparatus for automatically transferring a plurality of
wafers from a wafer holder to an etching drum, comprising: a
transfer chamber containing a liquid; a first stand disposed in the
liquid, the first stand including a plurality of first grooves each
sized to receive one of the plurality of wafers; a first lift for
supporting at least one wafer holder each configured to support a
plurality of the wafers; a second stand disposed in the liquid, the
second stand including a plurality of second grooves each sized to
receive one of the plurality of wafers; a second lift laterally
spaced from the first lift in the chamber for supporting in the
liquid an etching drum including a plurality of third grooves each
sized to receive one of the plurality of wafers; and a transfer
unit for (i) moving the first lift to transfer in the liquid the
plurality of wafers from the at least one wafer holder to the first
stand such that the first stand supports the plurality of wafers in
a desired relationship relative to each other, (ii) transferring in
the liquid the plurality of wafers from the first stand to the
second stand, and (iii) moving the second lift to transfer in the
liquid the plurality of wafers from the second stand to the etching
drum supported on the second lift such that the etching drum
supports the plurality of wafers in the desired relationship
relative to each other, wherein the plurality of wafers are
retained in the desired relationship during transfer between the at
least one wafer holder and the first stand, the first stand and the
second stand, and the second stand and the etching drum, and the
plurality of wafers are supported on the etching drum in the
desired relationship.
12. The apparatus of claim 11, wherein the transfer unit is
operable to (i) move the first lift relative to the first stand so
as to automatically transfer the plurality of wafers from the at
least one wafer holder to the first stand, and (ii) move the second
lift relative to the second stand so as to automatically transfer
the plurality of wafers from the second stand to the etching
drum.
13. The apparatus of claim 11, wherein the transfer unit comprises
a wafer engagement element that can grasp a plurality of wafers
supported on the first stand and position the plurality of wafers
on the second stand in the desired relationship.
14. The apparatus of claim 13, wherein the wafer engagement element
includes a plurality of fourth grooves each for receiving one of
the plurality of wafers, the fourth grooves of the wafer engagement
element having about the same spacing as the first, second and
third grooves.
15. The apparatus of claim 11, wherein the first lift includes a
wall having a through opening sized to receive the first stand when
the first lift is moved in the liquid to transfer the plurality of
wafers from the at least one wafer holder to the first stand, and
the second lift includes a wall having a through opening sized to
receive the second stand when the second lift is moved in the
liquid to transfer the plurality of wafers from the second stand to
the etching drum.
16. The apparatus of claim 11, wherein the transfer unit is
automatically operated to transfer the plurality of wafers.
17. The apparatus of claim 11, wherein the transfer unit is
operable in a reverse direction to transfer the wafers from the
etching drum to the second stand, from the second stand to the
first stand, and from the first stand to the at least one wafer
holder.
18. An apparatus for transferring wafers from a wafer holder to an
etching drum, comprising a transfer unit for automatically removing
at least one wafer supported on a wafer holder and transferring the
removed at least one wafer to an etching drum such that the at
least one wafer is supported on the etching drum.
19. The apparatus of claim 18, further comprising: a transfer
chamber; a first stand disposed in the transfer chamber; a first
lift for supporting the wafer holder; a second stand disposed in
the transfer chamber at a laterally spaced location from the first
stand; and a second lift disposed in the transfer chamber for
supporting the etching drum; wherein the transfer unit is operable
to (i) move the first lift to transfer the at least one wafer from
the wafer holder to the first stand, (ii) transfer the at least one
wafer from the first stand to the second stand, and (iii) move the
second lift to transfer the at least one wafer from the second
stand to the etching drum supported on the second lift.
20. A method of transferring wafers between wafer holders,
comprising: placing at least one wafer on a first wafer holder;
placing the first wafer holder in a liquid contained in a transfer
chamber; and automatically transferring the at least one wafer from
the first wafer holder to a second wafer holder disposed in the
liquid.
21. The method of claim 20, wherein the first wafer holder is a
wafer cassette and the second wafer holder is an etching drum.
22. The method of claim 20, wherein a first stand and a second
stand are disposed in the liquid, and the method further comprises:
automatically transferring the at least one wafer from the first
wafer holder to the first stand in the liquid; automatically
transferring the at least one wafer from the first stand to the
second stand in the liquid; and automatically transferring the at
least one wafer from the second stand to the second wafer holder in
the liquid.
23. The method of claim 22, wherein the first stand and the second
wafer holder each comprise a plurality of parallel grooves, each
groove is sized to receive one of the at least one wafers, and a
plurality of the wafers are transferred from the first wafer holder
to the second wafer holder substantially without cross-indexing of
the transferred wafers.
24. The method of claim 20, wherein a plurality of wafers are
transferred from the first wafer holder to the second wafer holder
(i) such that the plurality of wafers substantially do not contact
each other during transfer, and (ii) substantially without
cross-indexing of the transferred wafers.
25. The method of claim 22, wherein a plurality of wafers are
transferred simultaneously from the first wafer holder to the first
stand, simultaneously from the first stand to the second stand, and
simultaneously from the second stand to the second wafer
holder.
26. A method of transferring wafers between a wafer holder and an
etching drum, comprising: placing at least one wafer on a wafer
holder; and automatically removing the at least one wafer from the
wafer holder and transferring the at least one wafer to an etching
drum.
27. The method of claim 26, wherein a plurality of said at least
one wafer are transferred from the wafer holder to the etching drum
substantially without cross-indexing of the wafers.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention is directed to the field of semiconductor
wafer preparation and, more particularly, to an apparatus and
method for transferring wafers between wafer holders.
[0003] 2. Description of Related Art
[0004] During semiconductor wafer preparation, wafers are subjected
to mechanical processes including slicing, grinding and lapping,
which produce lattice damage in the surface regions of the wafers.
This lattice damage is generally removed by chemically etching the
wafers to remove the damaged surface regions of the wafers. Etching
is typically conducted in an etching machine, which includes an
etching drum to movably support the wafers within an acid etch
solution during the etching process.
[0005] During the etching process, it is important that the wafers
are positioned on the etching drum so that the wafers are parallel
to, and uniformly spaced from, each other. Such positioning of the
wafers is desirable so that the wafers do not contact and possibly
chip or scratch each other. The wafer surfaces are very sensitive
to such contact before etching (after cleaning). In addition,
uniform spacing of the wafers promotes uniform etching of the
wafers, so that etched wafers are uniformly sized and do not
include stained regions. Non-uniform etching can produce defective
wafers that are unsuitable for subsequent fabrication and must be
scrapped at substantial financial cost.
[0006] It is known to manually position wafers on etching drums.
The structure of etching drums makes it difficult, however, for
operators to manually position the wafers on the etching drums so
that the wafers are properly positioned in an efficient manner.
Particularly, etching drums typically have multiple sets of
grooves, with each set of grooves being designed to receive and
support a single wafer. Each set of grooves typically includes
several grooves that are aligned with each other. During manual
positioning of the wafers, operators must position the wafers so
that each of the wafers is properly received within each of the
grooves of one set of grooves only. If the wafers are not properly
positioned in this manner, they will be "cross-indexed" in the
grooves, meaning that individual wafers are received in the grooves
of more than one set of grooves. Consequently, more than one wafer
can be received in individual grooves, causing the wafers to not
all be parallel to, and equally spaced from, each other. As a
result, the wafers can physically contact each other. Such contact
can scratch the wafers and also prevent uniform etching of each
wafer, as described above.
[0007] In order to correct cross-indexing, operators must manually
re-position the wafers on the etching drum before etching. This
approach is not satisfactory, however, for several reasons. First,
the wafers are susceptible to scratching and, accordingly, it is
desirable to minimize such handling of the wafers. Second, it is
time-consuming for the operators to re-position the wafers and this
additional step can significantly delay the performance of the
etching step. Third, the environment of the etching machine can be
hazardous to operators due to the presence of the acid etch
solution and associated fumes. Correcting cross-indexing problems
can force the operators to be exposed to this environment for
extended periods of time.
[0008] Another concern during wafer preparation is to maintain the
wafers in a clean condition. For example, wafers are very sensitive
to contamination after being cleaned. Accordingly, it is important
to reduce exposure of the wafers to potential contamination during
transfer operations, such as by reducing exposure of cleaned wafers
to the ambient atmosphere prior to etching, so as to reduce
oxidation and contamination of the wafers.
[0009] Thus, there is a need for an apparatus and method for
transferring wafers from wafer carriers to etching drums that can
reduce or even eliminate cross-indexing, reduce exposure of
operators to hazardous wafer etching environments, and reduce wafer
contamination during processing and transfer operations.
SUMMARY OF THE INVENTION
[0010] This invention provides an apparatus for transferring wafers
between various types of wafer holders that can satisfy the above
needs.
[0011] The wafers can be semiconductor wafers as well as other
types of wafers and similar shaped objects.
[0012] The apparatus can be used to transfer wafers between various
types of wafer holders. For example, in some embodiments, the
apparatus can transfer wafers from wafer holders that hold wafers
in set relationships, such as parallel relationships, relative to
each other. The apparatus can automatically transfer wafers between
such wafer holders and retain the wafers in their desired
relationships during transfer. The apparatus can eliminate the need
for operators to manually transfer wafers between holders. In
addition, the apparatus can transfer wafers without cross-indexing
the wafers. Thus, the apparatus can eliminate the need for
operators to manually correct cross-indexing problems in
transferred wafers. Accordingly, the wafers can be prevented from
contacting and damaging each other during transfer.
[0013] The apparatus can be used to transfer wafers from wafer
cassettes, which are typically used to carry semiconductor wafers
during wafer preparation. The apparatus can be used to
automatically transfer wafers from wafer cassettes to etching drums
that are utilized in etching machines. In addition, the apparatus
can automatically transfer etching drums between the apparatus and
etching machines, so that manual transfer is not required.
[0014] According to an embodiment of this invention, the apparatus
comprises a transfer chamber for containing a liquid, and a
transfer unit for transferring at least one wafer in the liquid
from a first wafer holder to a second wafer holder. For example,
the first and second wafer holders can be a wafer cassette and an
etching drum, respectively. In some embodiments, the liquid is
preferably a high-purity liquid. By transferring wafers in the
liquid, the wafers can be protected against exposure to
contamination during transfer.
[0015] Although not limited to these specifics, in a particular
embodiment of this invention, the apparatus can comprise one or
more stands disposed in the liquid in the transfer chamber. During
transfer operations, the stands can support one or more of the
wafers in the liquid. The apparatus can further comprise a first
lift for supporting the first wafer holder and a second lift for
supporting the second wafer holder. The first lift can be moved by
the transfer unit to transfer one or more wafers from the first
wafer holder to the first stand in the liquid. The second lift can
be moved by the transfer unit to transfer one or more wafers from
the second stand to the second wafer holder in the liquid.
[0016] The transfer unit can also transfer wafers in the reverse
direction in the liquid, i.e., from the second wafer holder to the
second stand, from the second stand to the first stand, and from
the first stand to the first wafer holder. In addition, the
apparatus can transfer wafers to and from other machines used for
wafer fabrication, such as etching machines, that are utilized in
wafer preparation. Accordingly, wafers can be transferred back to a
wafer holder after the wafers are subjected to other wafer
fabrication steps.
[0017] The transfer unit is preferably automated so that it can
automatically transfer the wafers in the liquid between the various
wafer supports. Accordingly, the apparatus can eliminate the need
for operators to manually transfer wafers between wafer
holders.
[0018] This invention also provides a method for transferring
wafers between wafer holders in a liquid medium that utilizes the
apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Certain preferred embodiments of this invention will be
described in detail, with reference to the accompanying figures, in
which:
[0020] FIG. 1 is a partial perspective view of an apparatus for
transferring wafers between wafer holders in a liquid in accordance
with an embodiment of this invention, showing a cassette lift
supporting a pair of wafer cassettes in a raised position in a
transfer chamber;
[0021] FIG. 2 illustrates the manner of placing the wafer cassettes
onto the cassette FIG. 3 illustrates a transfer unit of the
apparatus according to an embodiment of this invention in a raised
position prior to being engaged with the cassette lift of FIG.
2;
[0022] FIG. 4 illustrates the transfer unit of FIG. 3 with the
wafer chucks of the transfer unit in a closed position;
[0023] FIG. 5 illustrates the transfer unit of FIG. 4 with the
wafer chucks in an open position in which the transfer unit is
fully engaged with the cassette lift in the raised position;
[0024] FIG. 6 illustrates the apparatus of FIG. 1 with the cassette
lift in the raised position and the wafer chucks engaged with the
cassette lift;
[0025] FIG. 7 illustrates the transfer unit and cassette lift of
FIG. 5 and the manner of disengaging cassette lift stop elements to
enable the cassette lift to be lowered into the liquid in the tank
by the transfer unit;
[0026] FIG. 8 illustrates the apparatus of FIG. 1 with the cassette
lift in a lowered position after the wafers contained in the wafer
cassettes are transferred to first wafer stands;
[0027] FIG. 9 shows the cassette lift of FIG. 2 in the lowered
position of FIG. 8, with a plurality of wafers positioned in a
parallel relationship on the first wafer stands;
[0028] FIG. 10 illustrates the apparatus of FIG. 8 after
disengaging the wafer chucks from the cassette lift and engaging
wafer engagement portions of the wafer chucks with the wafers;
[0029] FIG. 11 shows the transfer unit in a raised position above
the first wafer stands after removing the wafers from the first
stands, and the wafer cassettes in the lowered position in the
tank;
[0030] FIG. 12 illustrates the apparatus of FIG. 10 with the wafer
chucks in a raised position above second wafer stands prior to the
wafer chucks being engaged with the drum lift;
[0031] FIG. 13 shows the transfer unit in the raised position above
the second wafer stands with the wafer chucks in the closed
position supporting the wafers;
[0032] FIG. 14 shows the apparatus of FIG. 12 with the wafer chucks
opened and engaged with the drum lift and the cassettes supported
on the second wafer stands in the lowered position of the drum
lift;
[0033] FIG. 15 illustrates the wafers positioned in a parallel
relationship on the second stands and the etching drum in a lowered
position, with the arrow representing the direction of movement of
the etching drum to a raised position;
[0034] FIG. 16 illustrates the apparatus of FIG. 14 with the drum
lift in a raised position in which the wafers are supported by the
etching drum;
[0035] FIG. 17 illustrates the manner of closing the wafer chucks
and engaging the drum lift stop elements to hold the drum lift in
the raised position;
[0036] FIG. 18 illustrates the etching drum and drum lift in the
raised position after the drum chucks are disengaged from the drum
lift;
[0037] FIG. 19 illustrates the transfer unit after being disengaged
from the drum lift and being moved to a side of the etching drum
facing the first stands, showing a drum hand of the transfer unit
engaged with a shaft of the etching drum and a wafer holding bar of
the transfer unit engaged with a movable locking rod of the etching
drum;
[0038] FIG. 20 is an enlarged partial view showing the wafer
holding bar of the transfer unit engaged with the movable locking
rod of the etching drum, with the locking rod in an unlocked
position;
[0039] FIG. 21 illustrates an etching drum that can be used in the
apparatus of this invention; and
[0040] FIG. 22 illustrates the tank of the apparatus and a portion
of the transfer unit disposed above the tank.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0041] This invention provides an apparatus and method for
transferring wafers between various types of wafer holders. This
invention can be used to transfer wafers between wafer holders that
are conventionally used to contain wafers during wafer preparation.
For example, the wafer holders can be wafer cassettes, wafer boats,
etching drums and the like. The wafers can be semiconductor wafers
such as silicon wafers, gallium arsenide wafers and other
semiconductor materials. The wafers can be composed of
non-semiconductor materials as well, such as quartz wafers.
[0042] The apparatus of this invention can transfer wafers between
wafer holders such that the wafers are retained in a desired
orientation relative to each other during and after transfer. For
example, wafers are typically supported by wafer holders in a
parallel relationship, such as in individual grooves, to prevent
contact between individual wafers. The apparatus can transfer
wafers between various types of wafer holders and retain such
parallel relationship of the wafers.
[0043] The apparatus can transfer wafers automatically, thus
eliminating the need for operators to manually handle the wafer
holders or wafers during transfer operations. In addition, this
invention can reduce exposure of wafers to contamination during
transfer, and can eliminate physical damage to wafers that can
occur during manual handling operations.
[0044] The above and other advantages of this invention will be
described below with reference to the drawings. The figures
illustrate the transfer of wafers between wafer cassettes and an
etching drum. The etching drum is utilized in an etching machine to
etch the wafers. The etching machine does not form a part of this
invention and, accordingly, is not illustrated or described in
detail herein. It will be understood by those skilled in the art
that the apparatus of this invention can be used to transfer wafers
between different types of wafer holders as well such as, for
example, between different wafer cassettes or different etching
drums. In addition, it will be understood that the wafers can be
transferred between more than two different wafer holders.
[0045] FIG. 1 illustrates a portion of an apparatus 10 according to
an embodiment of this invention that can be used to transfer wafers
between wafer holders in a liquid environment. The illustrated
apparatus includes a tank 12 shown partially broken away. The tank
is typically open at the upper end as shown. The tank includes
upstanding side walls 14, 16 and a bottom wall 18 forming a
housing. The housing defines a transfer chamber 20 for containing a
liquid that functions as the wafer transfer medium. The liquid can
be any suitable high-purity liquid that is non-contaminating to the
apparatus and to the wafers. Typically, the liquid is high-purity
deionized water. The liquid level L in the transfer chamber is
typically approximately as shown in FIG. 1.
[0046] According to an aspect of this invention, the liquid in the
tank 12 can comprise a chemical that forms an oxide layer on the
wafers, to protect the wafers from scratching due to contact
between each other. For example, the liquid can comprise
high-purity water and up to about 5% of hydrogen peroxide. Other
suitable chemicals that promote oxide layer formation can be used
as well.
[0047] The apparatus 10 can also include a liquid supply system
that circulates the liquid into and out of the tank. The liquid
supply system can include a liquid inlet 22 and a liquid outlet 24
or an alternative overflow system to enable the liquid to be filled
into the tank 12 to maintain the liquid in the tank in a clean
condition. In addition, the liquid supply system can maintain a
desired liquid level in the tank 12. However, it will be readily
apparent that such a liquid supply system is not necessary in all
embodiments of this invention, and that wafer contamination by the
liquid can be prevented in other manners.
[0048] It will be understood by those skilled in the art that the
apparatus 10 of this invention can be used to transfer wafers
between wafer holders when no liquid is contained in the tank 12.
In such embodiments, the wafers can also be transferred without
requiring operators to handle the wafers. It is preferable,
however, to transfer wafers in a liquid for at least the following
reasons. First, the high-purity liquid prevents the wafers from
being exposed to the atmosphere during the transfer operation,
thereby eliminating contamination of the wafers by the air during
transfer. Second, the increased viscosity of the liquid as compared
to the air can assist in maintaining the wafers in the desired
relative orientation with respect to each other during
transfer.
[0049] The apparatus 10 further comprises a cassette lift 26 and a
drum lift 28 laterally spaced from the cassette lift 26. The
cassette lift 26 is shown in a fixed, raised position in FIG. 1.
Referring also to FIG. 2, the cassette lift 26 includes a bottom
wall 30 and opposed upstanding side walls 32. The bottom wall 30 is
sized to support at least one wafer cassette 34 (two wafer
cassettes 34 are shown). More or less wafer cassettes 34 can be
used in other embodiments of this invention. Each wafer cassette 34
typically includes a plurality of parallel grooves 36, which are
each sized to support one wafer, such that the wafer cassettes can
support a plurality of wafers in a parallel relationship. For
simplification, only one wafer W is shown in each wafer cassette 34
in some figures, such as FIG. 1. In other figures such as FIG. 2, a
plurality of wafers W are shown in the wafer cassettes 34 to
illustrate how the wafers can be supported in various relationships
such as the illustrated parallel relationship. Each wafer cassette
34 is typically sized to support about 25 or less wafers. One or
more holes 38 extend through the bottom wall 30 of the cassette
lift 26. The number of holes 38 can be varied depending on the
number of wafer cassettes 34 supported on the cassette lift 26. The
side walls 32 each include two slots 40 that are typically
generally L-shaped. The slots 40 each typically include a vertical
portion 42 and a horizontal portion 44. The horizontal portions 44
extend outwardly in opposite directions to each other.
[0050] A first cassette lift stop element 46 is provided on the
outer surface 48 of each of the side walls 32 of the cassette lift
26. The first cassette lift stop elements 46 each releasingly
engage a second cassette lift stop element 50 provided on the side
walls 14 of the tank 12 as shown in FIG. 1, to hold the cassette
lift 26 in the vertically fixed, raised position. The first and
second cassette lift stop elements 46, 50 can be selectively
disengaged from each other by moving the second cassette lift stop
elements 50 away from the first cassette lift stop elements 46 to
enable the cassette lift 26 to be moved vertically downward in the
tank 12 as described in greater detail below. One or more rollers
52 are provided on each side wall 32 of the cassette lift 26. The
rollers 52 mate with vertically extending rails 54 which are
mounted to each of the opposed side walls 14 of the tank 12, to
enable the cassette lift 26 to be moved vertically in the tank 12
in the direction of the rails 54.
[0051] The cassette lift 26 supports the wafer cassettes 34 prior
to transferring wafers from the cassette lift 26 to one or more
first wafer stands 56 of the apparatus 10. As shown, a pair of
laterally spaced first wafer stands 56 are mounted to, and extend
upwardly from, the bottom wall 18 of the tank 12. In embodiments in
which more or less than two wafer cassettes 34 are utilized, the
apparatus 10 can include a number of first stands 56 corresponding
to the number of wafer cassettes 34. The first wafer stands 56 can
each include a pair of upstanding legs 58 and a wafer basket 60
attached to the upper ends of the legs 58. The wafer baskets 60
include a upper surface 62 in which a plurality of parallel grooves
64 are formed. The upper surface 62 is typically concave to match
the configuration of the wafers. The grooves 64 are each sized to
receive and support one wafer in a vertical orientation, such that
the first wafer stands 56 can each support a plurality of wafers in
a parallel relationship, as depicted in FIG. 9. In the illustrated
relationship, the wafers are spaced from each so that no contact
occurs between the wafers.
[0052] The drum lift 28 typically can have a construction similar
to that of the cassette lift 26. As shown, the drum lift 28 can
comprise opposed upstanding side walls 66 and a bottom wall 68. The
side walls 66 are spaced from each other by a distance greater than
the length of an etching drum 70 that is supported on the drum lift
28. The side walls 66 each include a slot 72 that is typically
generally L-shaped slot 72 (FIG. 8). The slots 72 can include a
vertical portion 74 and a horizontal portion 76. A first drum lift
stop element 78 is provided on the outer surface of each side wall
66 of the drum lift 28. The first drum lift stop elements 78 each
engage a second drum lift stop element 80 provided on the side
walls 14 of the tank 12, to maintain the drum lift 28 in a
vertically fixed position. One or more rollers 82 are provided on
each side wall. The rollers 82 mate with vertically extending rails
84 mounted to each of the opposed side walls 14 of the tank 12,
such that the drum lift 28 is vertically movable in the tank 12
along the direction of the rails 84.
[0053] The bottom wall 68 of the drum lift includes one or more
holes 86 which extend through the bottom wall 68 (FIG. 17). The
number of holes 86 typically equals the number of holes 38 in the
cassette lift 26. One or more second wafer stands 88 (two are
shown) are mounted to the bottom wall 18 of the tank 12 (see FIG.
8). The second wafer stands 88 each include each include a pair of
upstanding legs 90 and a wafer basket 92 attached to the upper ends
of the legs 90. The wafer baskets 92 include a concave upper
surface 94 defining a plurality of parallel grooves 96. The grooves
96 are each sized to receive and support a wafer in a vertical
orientation, such that the second wafer stands 88 can each support
a plurality of wafers in a parallel relationship. As described
below, the holes 86 in the bottom wall 68 of the drum lift 28 are
each configured to receive the wafer basket 92 of one of the second
wafer stands 88 during wafer transfer.
[0054] It will be understood by those skilled in the art that the
number of second wafer stands 88 can vary in embodiments of this
invention. In the illustrated embodiment, the apparatus 10
comprises two second wafer stands 88, which equals the number of
first wafer stands 56. However, the number of first and second
wafer stands can be different in some embodiments. Furthermore, the
size of the wafer baskets 60, 92 of the first and second wafer
stands 56, 88, respectively, can be varied to vary the wafer
holding capacity. For example, a single wafer stand 88 including a
wafer basket 92 having the wafer holding capacity of the two
illustrated wafer baskets 92 combined can alternatively be used
instead of two second wafer stands 88. Such configurations are also
possible for the first wafer stand 56.
[0055] The drum lift 28 supports the etching drum 70 in the tank 12
so as to enable transfer of the wafers from the first wafer stands
56 to the second wafer stands 88, and from the second wafer stands
88 to the etching drum 70, as described in detail below.
[0056] An embodiment of the etching drum 70 that can be used in the
apparatus 10 is illustrated in greater detail in FIG. 21. As shown,
the etching drum 70 comprises a plurality of laterally spaced
plates 93, 94. The plates are typically arranged in a parallel
relationship relative to each other as shown. The plates 93, 94
each include an arcuate shaped through hole 96. A plurality of
fixed rods 98 and a movable locking rod 100 extend longitudinally
along the etching drum 70. The fixed rods 98 connect the plates 93,
94 together and maintain the plates 93, 94 in a fixed relationship
relative to each other. The fixed rods 98 and the locking rod 100
each include a plurality of grooves 102. The grooves 102 in each
rod are each aligned with a groove in each of the other respective
rods, and the aligned groups of four grooves 102 can each receive
and support one of the wafers. The locking rod 100 extends through
the arcuate shaped through holes 96 of each of the plates 93, 94
and is movable along the arcuate shaped through holes 96 between an
upper, locking position shown in phantom line and an illustrated
lower, unlocking position, as represented by the arrows A. A
plurality of wafers can be supported in the grooves 102 when the
movable rod 100 is in the unlocking position, such that the wafers
can be selectively removed from the etching drum 70. The plurality
of wafers can be supported in the grooves 102 when the movable rod
100 is in the locking position, such that the wafers cannot be
accidentally or intentionally removed from the etching drum 70.
[0057] The etching drum further comprises a central shaft 104 which
extends outwardly from each of the end plates 94. To support the
etching drum 70, vertical slots (not shown) are formed in the inner
surface of each of the side walls 66 of the drum lift 28. The shaft
104 can be inserted into the respective slots in a downward
direction to support the etching drum 70 on the drum lift. As
described below, the etching drum 70 can be lifted such that the
shaft 104 is moved upwardly in the respective slots to remove the
etching drum 70 from the drum lift 28. The etching drum 70 also
includes a gear mechanism 106 that can engage mating gears in a
conventional etching machine when the etching drum 70 is placed in
the etching machine to etch the wafers following wafer
transfer.
[0058] As shown in some of the figures, including FIGS. 3, 4, 5, 7,
11, 13, 17 and 19, the apparatus 10 comprises a transfer unit 110
that performs multiple functions during wafer transfer, enabling
wafers to be automatically transferred between different wafer
holders. The wafer transfer unit 110 also enables wafers to be
transferred to and from machines, such as an etching machine, that
are utilized in wafer fabrication.
[0059] In the illustrated embodiment, the transfer unit 110 enables
a plurality of wafers to be automatically, simultaneously
transferred from wafer holders such as the wafer cassettes 34 to
other wafer holders such as the etching drum 70. During this
transfer process, the wafers are transferred from the wafer
cassettes 34 to the first wafer stands 56, from the first wafer
stands 56 to the second wafer stands 88, and from the second wafer
stands 88 to a second wafer holder such as the etching drum 70.
These wafer transfer steps can each be performed in the liquid
contained in the tank 12, such that the wafers are not exposed to
the ambient environment during transfer between the wafer holders.
In addition, the wafers can be transferred during each of these
steps such that the wafers are retained in a desired relationship
to each other, such as in a parallel relationship shown in some
figures.
[0060] Only the relevant portions of the transfer unit 110 needed
for illustrative purposes are shown in detail in the figures and
described below. As shown in FIG. 3, an embodiment of the transfer
unit 110 comprises a body portion 112 including opposed end faces
114, opposed side faces 116 and a top face 118. The body portion
112 can have other shapes as well, including other rectangular
shapes.
[0061] Referring to FIG. 22, the transfer unit 110 also includes a
drive mechanism 122 that moves the body portion 112 relative to the
tank 12. The drive mechanism 122 can include two pairs of arms 124,
126. Each pair of arms 124, 126 are pivotally connected at upper
ends to a mounting surface 127 and at lower ends to one of the
opposed end faces 114 of the body portion 112 of the transfer unit
110. The arms 124, 126 are vertically movable and are also pivotal
about pivot axes 129 to move the transfer unit 110 vertically and
laterally in the tank 12 as described below. The drive mechanism
122 can also include drive elements (not shown) for moving the arms
124, 126. The operation of the drive elements can be controlled by
an operator of the apparatus 10. For example, the operation of the
apparatus 10 can be automatically programmed so that the transfer
unit 110 performs the operations described below in an automated
manner, so that the operator needs only to start the transfer
process and to stop the operation of the apparatus after transfer
is completed.
[0062] A pair of wafer chucks 128, 130 are provided on the bottom
face 120 of the body portion 112. The wafer chucks 128, 130 each
include a rod 132 and one or more wafer engagement portions 134
attached on the rod 132. (In FIGS. 6, 8, 10, 12, 14 and 16, only
the wafer chucks 128, 130 of the transfer unit 110 are shown for
simplification.) The rods 132 are typically cylindrical shaped as
shown, and can optionally have other shapes such as rectangular.
The wafer engagement portions 134 each include an inner surface 136
including a plurality of grooves 138 each sized to receive a wafer
(only the grooves 138 of the wafer chucks 130 are shown). The inner
surface 136 of each wafer engagement portion 134 is typically
concave shaped to match the circumferential shape of the wafers.
The grooves 138 are preferably parallel to each other. As described
in greater detail below, the wafer chucks 128, 130 are moved
automatically toward and away from each other during wafer transfer
operations. The wafer chucks 128, 130 can be moved toward and away
from each by a retractable pneumatic-operated rod or the like (not
shown).
[0063] The operation of the wafer transfer apparatus 10 will now be
described with reference to the drawing figures which sequentially
illustrate a series of steps that can be automatically performed by
the wafer transfer apparatus during the transfer of wafers from the
wafer cassettes 34 to the etching drum 70 disposed on the drum lift
28. In these figures, only portions of the apparatus 10 are
illustrated for simplicity and clarity. As shown in FIG. 2, open
H-bar sides of the wafer cassettes face toward each other to enable
bar codes on the wafers to be automatically read before and after
wafer cassette 34 transfer.
[0064] FIG. 2 shows the manner of placing two wafer cassettes 34
onto the cassette lift 26. This step is typically performed
manually by an operator, with the wafer cassettes 34 being
positioned above the liquid in the tank 12. The wafer cassettes 34
each have an open bottom. One of the wafer cassettes 34 is shown
positioned over one of the holes 38 in the bottom wall 30 of the
cassette lift 26. The other wafer cassette 34 is shown before being
lowered onto the cassette lift 26 over the other hole 38. The
cassette lift 26 is retained in a fixed upper position in which the
wafer cassettes 34 are positioned above the liquid in the tank, by
engagement of the first and second cassette lift stop elements 46,
50, as shown in FIG. 2.
[0065] FIG. 3 shows the transfer unit 110 positioned above the
cassette lift 26 before the transfer unit 110 is engaged with the
cassette lift 26. The transfer unit 110 is engaged with the
cassette lift 26 by lowering the transfer unit 110 such that the
outer portions of the rods 132 of the wafer chucks 128, 130 are
inserted into the vertical portions 42 of the slots 40 on the side
walls 32 as shown in FIG. 4. Once the rods 132 reach the bottom
ends of the vertical portions 42, the wafer chucks 128, 130 are
moved horizontally away from each other (opened) such that the rods
132 are moved into the horizontal portions 44 of the slots 40, as
shown in FIGS. 5 and 6.
[0066] To next lower the cassette lift 26 into the liquid in the
tank 12, the second cassette lift stop element 50 is moved
horizontally to disengage from the first cassette lift stop element
46 as depicted by the arrow B in FIG. 7. The transfer unit 110 can
then be lowered as depicted by the arrow C to lower the cassette
lift 26 into the liquid in the tank 12. The transfer unit 110
lowers the cassette lift 26 into the liquid such that the holes 38
in the bottom wall 30 of the cassette lift 26 move downwardly so as
to each receive one of the first wafer stands 56. FIGS. 8 and 9
show the cassette lift 26 in a bottom position in which the first
wafer stands 56 extend upwardly through the holes 38 and the wafers
are transferred from the wafer cassettes 34 to the respective wafer
baskets 60. The wafer baskets 60 can support the wafers in the same
orientation as the wafers are supported on wafer cassettes 34. The
wafer cassettes 34 are positioned substantially below the wafer
baskets 60.
[0067] The wafers are next transferred from the first wafer stands
56 to the drum lift 28. Referring to FIG. 10, in order to transfer
the wafers from the first wafer stands 56, the wafer chucks 128,
130 are brought toward each other (closed) so that pairs of opposed
grooves 138, including a groove 138 of each opposed wafer
engagement portion 134, each receive one of the wafers. The wafer
engagement portions 134 support the wafers in a parallel
relationship relative to each other as shown. FIG. 11 shows the
wafer transfer unit 110 in a raised position above the first wafer
stands 56 after the wafers have been engaged and lifted off of the
first wafer stands 56 by the wafer transfer unit 110.
[0068] The wafers supported by the wafer chucks 128, 130 are then
moved laterally in the tank 12 to the drum lift 28. The wafers are
positioned above the second wafer stands 88 as shown in FIG. 12 and
lowered onto the second wafer stands 88 as shown in FIG. 13. The
wafers are positioned in the same parallel orientation on the
second wafer stands 88 as on the first wafer stands 56. FIGS. 13
and 14 show the drum lift 28 and etching drum 70 in a lowered
position at this stage of the wafer transfer operation.
[0069] Next, the wafers are transferred from the second wafer
stands 88 to the etching drum 70. This is achieved by lifting the
drum lift 28 and supported etching drum 70 upwardly in the tank 12
in the direction of the arrow D shown in FIG. 15. To lift the drum
lift 28 and etching drum 70, the rods 132 of the wafer chucks 128,
130 of the wafer transfer unit 110 are engaged in the horizontal
portions 76 of the slots 72 formed in the drum lift 28 and the
wafer transfer unit 110 is raised until the wafers supported on the
second wafer stands 88 are supported by the rods 98, 100 of the
etching drum 70 as shown in FIG. 16.
[0070] The wafer transfer unit 110 is then disengaged from the drum
lift 28 by moving the rods 132 of the wafer chucks 128, 130 toward
each other as represented by the arrows E, E in FIG. 17. FIG. 18
shows the drum lift 28 after the wafer transfer unit 110 is
disengaged. The drum lift 28 is held in the fixed raised position
by engagement of the drum lift stop elements 78, 80 as depicted by
the arrow F in FIG. 17 and shown in FIG. 18.
[0071] The etching drum 70 is then removed from the drum lift 28 by
the wafer transfer unit 110. Specifically, the wafer transfer unit
110 is moved to the side of the etching drum 70 that faces the
cassette lift 26 (front side). As shown in FIGS. 19 and 20, the
wafer transfer unit 110 includes a pair of drum hands 140 which are
each configured to support the shaft 104 of the etching drum 70.
The wafer transfer unit 110 can also include a pair of wafer
holding bars 142 that engage the locking rod 100 of the etching
drum 70 and move the locking rod 100 from the unlocking to the
locking position as depicted by arrow F. After the drum hands 140
are moved to support the etching drum 70, the wafer transfer unit
110 lifts the etching drum 70 upwardly and away from the drum lift
28.
[0072] The etching drum 70 can then be removed from the liquid in
the tank 12 and moved by the wafer transfer unit 110 to another
wafer fabrication location. Typically, the etching drum 70 is moved
to the etching machine to etch the wafers. Following etching, the
wafer transfer unit can move the etching drum 70 and wafers back to
the apparatus 10. The wafers can then be transferred from the
etching drum 70 to the wafer cassettes 34 by performing the
above-described transfer steps in reverse order. Accordingly, the
apparatus 10 can be utilized to automatically transfer wafers to
and from an etching machine without an operator having to manually
handle the wafers during this transfer.
[0073] According to an aspect of this invention, the apparatus is
preferably composed of materials that are non-contaminating to the
liquid in the tank and to the wafers. For example, the components
of the apparatus that are exposed to the liquid in the tank can be
composed of non-metallic materials such as polyvinyl chloride
(PVC), polytetrafluoroethylene (PTFE) and the like. Other
components that are not exposed to the liquid can be composed of
the same non-metallic materials, as well as metals such as
stainless steels with a non-metallic material coating.
[0074] The etching drum 70 is composed of materials that are
resistant to chemical attack in the etching machine. Suitable
plastic materials are typically used to form the etching drum
70.
[0075] While this invention has been described in conjunction with
the specific embodiments described above, it is evident that many
alternatives, modifications and variations are apparent to those
skilled in the art in view of this disclosure. Accordingly, the
preferred embodiments of this invention as set forth above are
intended to be illustrative and not limiting. Various changes can
be made without departing from the spirit and scope of this
invention as defined in the following claims.
* * * * *