U.S. patent application number 10/985949 was filed with the patent office on 2005-04-21 for flat-object holder and method of using the same.
Invention is credited to Kimura, Yusuke, Mori, Takashi, Shimobeppu, Yuzo, Shinjo, Yoshiaki, Teshirogi, Kazuo, Watanabe, Mitsuhisa, Yajima, Koichi, Yoshimoto, Kazuhiro.
Application Number | 20050085171 10/985949 |
Document ID | / |
Family ID | 26623966 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050085171 |
Kind Code |
A1 |
Shimobeppu, Yuzo ; et
al. |
April 21, 2005 |
Flat-object holder and method of using the same
Abstract
A flat-object holder can hold a flat object-and-frame assembly,
and the holder has the flat object fixed to the frame with
protection tape. The flat-object holder includes at least a flat
object supporting area for fixedly holding the flat object via the
protection tape by applying a suction force, and a frame fixing
area for fastening the frame. The flat-object holder bearing the
flat object-and-frame assembly can be fixedly held by a selected
chuck table by applying a negative pressure to the flat object
supporting area. The flat-object holder can transfer and put the
flat object-and-frame assembly in a container. Thus, no matter how
thin the flat object may be, it can be handled without the fear of
breaking.
Inventors: |
Shimobeppu, Yuzo; (Kanagawa,
JP) ; Teshirogi, Kazuo; (Kanagawa, JP) ;
Yoshimoto, Kazuhiro; (Kanagawa, JP) ; Watanabe,
Mitsuhisa; (Kanagawa, JP) ; Shinjo, Yoshiaki;
(Kanagawa, JP) ; Mori, Takashi; (Tokyo, JP)
; Yajima, Koichi; (Tokyo, JP) ; Kimura,
Yusuke; (Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26623966 |
Appl. No.: |
10/985949 |
Filed: |
November 12, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10985949 |
Nov 12, 2004 |
|
|
|
10208104 |
Jul 31, 2002 |
|
|
|
6837776 |
|
|
|
|
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 37/30 20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 007/30 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2001 |
JP |
2001/320575 |
Nov 30, 2001 |
JP |
2001/366853 |
Claims
1. A flat-object holder for holding a flat object-and-frame
assembly having a flat object fixed to a frame with a protection
tape comprising at least a flat object supporting area for fixedly
holding the flat object via the protection tape by applying a
suction force, and a frame fixing area for fastening the frame.
2. A flat-object holder according to claim 1, wherein the flat
object supporting area is formed by a porous member.
3. A flat-object holder according to claim 2, wherein the frame has
an opening for accommodating the flat object and a tape applying
area encircling the opening for having the protection tape applied
thereto, the frame fixing area being at a level lower than the flat
object supporting area.
4. A flat-object holder according to claim 3, wherein the top
surface of the frame when being fastened to the frame fixing area
is positioned at a level lower than the upper surface of the flat
object supporting area.
5. A flat-object holder according to claim 1, wherein the frame
fixing area comprises a frame fastening section and frame releasing
means.
6. A flat-object holder according to claim 2, wherein the frame
comprises a ring-like body defining an opening for accommodating
the flat object and using its brim or inner circumference as a
protection tape support, the frame fixing area being at a level
lower than the upper surface of the flat object supporting area,
whereby the protection tape may be fixedly stretched between the
outer circumference of the flat object supporting area and the
inner circumference of the ring-like frame.
7. A flat-object holder according to claim 6, wherein the frame has
tightening-and-loosing means associated therewith.
8. A flat-object holder according to claim 1, wherein it is so
constructed that a plurality of frames each holding a flat-object
therein may be laid on each other.
9. A flat-object holder according to claim 8, wherein it has a
recess made on its bottom to accommodate the flat object of the
lower flat-object holder in non-contact fashion when two or more
flat-object holders are laid on each other; the flat-object holder
has a bearing section formed on its top to abut on the
circumference of the bottom recess of the upper flat-object holder
for bearing the upper flat-object holder; and the flat-object
holder has a riding section formed on its bottom to surround the
bottom recess and ride on the bearing section of the lower
flat-object holder.
10. A flat-object holder according to claim 1, wherein the flat
object supporting area has temperature-controlling means embedded
therein.
11. A flat-object holder according to claim 10, wherein the
temperature controlling means is capable of heating or cooling a
selected area of the flat object.
12. A flat-object holder according to claim 10, wherein the
temperature controlling means includes a pipe for permitting
thermal medium to pass therein, an electric heating wire or a
Peltier element.
13. A flat-object holder according to any of claim 1, wherein it
further comprises identification means.
14. A flat-object holder according to claim 13, wherein the
identification means includes barcodes or IC chips.
15-18. (canceled).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a flat-object holder for
use in holding semiconductor wafers or other thin, flat objects,
and to a method of using such flat-object holders.
[0003] 2. Related Arts
[0004] Referring to FIG. 27, a semiconductor wafer W1 has a
plurality of ICs, LSIs or other circuits formed thereon, and it has
a protection tape T applied to its front side for protecting the
circuits. The semiconductor wafer W1 is put on a chuck table 70
with its protection tape directed down, thereby permitting the rear
side of the semiconductor wafer to be ground with a grindstone 71
until a predetermined thickness has been reached. To meet the
recent tendency of reducing the size and weight of cellular phones,
notebook-sized personal computers and other electronic devices, it
is required that parts of such devices be down-sized accordingly,
and semiconductor wafers need to be ground until their thickness is
100 or less .mu.m thick, or 50 or less .mu.m thick.
[0005] If semiconductor wafers are ground to be 200 to 400 .mu.m
thick, they are thick and strong enough to facilitate their
transfer in the grinding apparatus or insertion in containers
without fear of their being broken. However, semiconductor wafers
whose thickness is reduced to be 50 to 100 .mu.m cannot be
transferred with ease because of their fragility.
[0006] Referring to FIG. 28, a semiconductor wafer W2 has grooves
72 made in the form of a lattice on its front side, each groove
being deep enough to be equal to the thickness of each of the
semiconductor chips, into which the semiconductor wafer W2 is to be
diced. The semiconductor wafer W2 is ground on its rear side until
the grooves 72 appear on the rear side to divide the semiconductor
wafer into squares. This is called a "pre-dicing" method. Such
square pieces, however, are too fragile to hold their appearance
free of any defects.
[0007] In an attempt to avoid such inconvenience, protection tapes
of good strength, for instance, made of polyethylene terephthalate
are applied to semiconductor wafers. Such reinforced semiconductor
wafers or chips can be transferred or put in containers without
fear of breaking. Disadvantageously, such protection tapes cannot
be peeled off the semiconductor wafers or chips without
difficulty.
[0008] Referring to FIG. 29, a semiconductor wafer W is fixedly
held by an annular frame F with the aid of an adhesive protection
tape T to be convenient for dicing. Such wafer-and-frame assemblies
are convenient for handling in transport or for putting in
containers, and the protection tapes can be removed from the thin
wafers or chips with ease. Disadvantageously the grinding machine
needs to be modified so that its chuck table may hold the
wafer-and-frame assembly.
[0009] In view of the above, there has been a demand for handling
fragile flat objects such as semiconductor wafers easily when
transporting; permitting the chuck table to hold such fragile flat
objects without the necessity of redesigning the chuck table; and
removing semiconductor wafers from their protection tapes with ease
after being grounded.
SUMMARY OF THE INVENTION
[0010] In the hope of solving the problems described above, a
flat-object holder for holding a flat object-and-frame assembly
having a flat object fixed to its frame with a protection tape
according to the present invention comprises at least a flat object
supporting area for fixedly holding the flat object via the
protection tape by applying a suction force, and a frame fixing
area for fastening the frame.
[0011] The flat object supporting area may be provided by a porous
member. In addition, the frame may have an opening for
accommodating the flat object and a tape applying area encircling
the opening for having the protection tape applied thereto, the
frame fixing area being at a level lower than the flat object
supporting area.
[0012] The top surface of the frame when being fastened to the
frame fixing area may be positioned at a level lower than the upper
surface of the flat object supporting area, and the frame fixing
area may comprise a frame fastening section and frame releasing
means. The frame may also comprise a ring-like body defining an
opening for accommodating the flat object, and using its brim or
inner circumference as a protection tape support, the frame fixing
area being at a level lower than the upper surface of the flat
object supporting area. Thus, the protection tape may be fixedly
stretched between the outer circumference of the flat object
supporting area and the inner circumference of the ring-like
frame.
[0013] The frame may have tightening-and-loosing means associated
Therewith, and the flat-object holder may be constructed so that a
plurality of frames each holding a flat-object therein may be laid
on each other. In addition, the flat-object holder may have a
recess on its bottom to accommodate the flat object of the lower
flat-object holder in a non-contact fashion when two or more
flat-object holders are laid on each other. The flat-object holder
may have a bearing section formed on its top to abut the
circumference of the bottom recess of the upper flat-object holder
for bearing the upper flat-object holder, and the flat-object
holder may have a riding section formed on its bottom to surround
the bottom recess and ride on the bearing section of the lower
flat-object holder.
[0014] The flat object supporting area may have a
temperature-controlling means embedded therein. The temperature
controlling means may be capable of heating or cooling a selected
area of the flat object. The temperature controlling means may also
include a pipe for permitting a thermal medium to flow therein, an
electric heating wire or a Peltier element.
[0015] The flat-object holder may further comprise identification
means, and the identification means may include bar codes or IC
chips.
[0016] A method of using a flat-object holder in a grinding machine
comprising a chuck table for holding flat objects by applying
negative pressure for suction, and a grinding means for grinding
the flat objects fixedly sucked onto the chuck table, may comprise
putting flat-object holders as described above on the chuck table;
grinding the flat object fixedly held by a selected flat-object
holder with the grinding means; removing the flat object from the
chuck table after grinding; and transporting the flat object thus
removed from the chuck table.
[0017] The method may further comprise, subsequent to the grinding
of the flat object of the selected flat-object holder, applying a
die-attachment film to the flat object; applying a dicing tape to
the die-attachment film; and applying a dicing frame onto the outer
circumference of the dicing tape.
[0018] The method may further comprise, subsequent to the step of
applying the dicing frame onto the outer circumference of the
dicing tape, the step of removing the dicing frame, the flat-object
holder, and the protection tape all together from the flat object.
The flat objects may be semiconductor wafer, rearranged, wired
semiconductor substrates or rearranged, wired and resin-sealed
semiconductor substrates.
[0019] Thanks to the holding of a thin, flat object with its frame
via an associated protection tape as a whole, such a fragile object
can be held in a stable and safe fashion, and can be held by the
chuck table without the necessity of redesigning the chuck table in
a grinding machine.
[0020] Other objects and advantages of the present invention will
be understood from the following description of preferred
embodiments of the present invention, which are shown in
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of a flat-object holder
according to a first embodiment of the present invention;
[0022] FIG. 2 is a longitudinal section of the flat-object
holder;
[0023] FIG. 3 is a perspective view of a wafer-and-frame assembly
having a wafer combined with its frame via a protection tape;
[0024] FIG. 4 is a perspective view of a frame;
[0025] FIG. 5 is a longitudinal section of a flat-object holder,
showing how a wafer-and-frame assembly can be supported;
[0026] FIG. 6 is a perspective view of a grinding machine;
[0027] FIG. 7 is a perspective view of the chuck table of the
grinding machine, a flat-object holder, and a wafer-and-frame
assembly having a wafer combined with its frame via a protection
tape;
[0028] FIG. 8 illustrates, in section, how a wafer is grounded;
[0029] FIG. 9 is a perspective view of a flat-object holder
according to a second embodiment of the present invention;
[0030] FIG. 10 is a perspective view of a wafer-and-frame assembly
having a wafer combined with its frame via a protection tape;
[0031] FIG. 11 is a perspective view of the ring-like frame;
[0032] FIG. 12 is a longitudinal section of a flat-object holder,
showing how a wafer-and-frame assembly can be supported;
[0033] FIG. 13 is a perspective view of the chuck table of the
grinding machine, the flat-object holder, and the wafer-and-frame
assembly;
[0034] FIGS. 14(A) to 14(K) illustrate one example of applying a
dicing tape to the semiconductor wafer, which is laid on a
flat-object holder, and of removing the flat-object holder from the
semiconductor wafer;
[0035] FIGS. 15(A) to 15(L) illustrate another example of applying
the dicing tape to the semiconductor wafer, which is laid on the
flat-object holder, and of removing the flat-object holder from the
semiconductor wafer;
[0036] FIG. 16 is a plane view of a tightening-and-loosening
frame;
[0037] FIG. 17 illustrates, in section, a flat-object holder
capable of being stacked;
[0038] FIG. 18 illustrates, in section, how a plurality of
flat-object holders can be laid on each other;
[0039] FIG. 19 is a perspective view of a first example of a
flat-object holder having a temperature controlling means embedded
therein;
[0040] FIG. 20 is a perspective view of a second example of a
flat-object holder having a temperature-controlling means embedded
therein;
[0041] FIG. 21 is a perspective view of a third example of a
flat-object holder having a temperature-controlling means embedded
therein;
[0042] FIG. 22 is a sectional view of a fourth example of a
flat-object holder having a temperature-controlling means embedded
therein;
[0043] FIG. 23 is a perspective view of a first example of a
flat-object holder having an identification means provided
therewith;
[0044] FIG. 24 is a perspective view of a second example of a
flat-object holder having an identification means provided
therewith;
[0045] FIG. 25 is a perspective view of a third example of a
flat-object holder having an identification means provided
therewith;
[0046] FIG. 26 shows a management system using a flat-object holder
according to the present invention;
[0047] FIG. 27 illustrates a conventional manner in which a
semiconductor wafer is supported by a selected chuck table in a
grinding machine;
[0048] FIG. 28 illustrates, in section, a conventional pre-dicing
mode according to which a semiconductor wafer is diced while being
supported by a selected chuck table in a grinding machine; and
[0049] FIG. 29 is a perspective view of a conventional
semiconductor wafer-and-frame assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0050] FIG. 1 shows a flat-object holder 10 according to a first
embodiment of the present invention. The flat-object holder 10
comprises a flat object supporting area 11 to be formed
corresponding to the shape and size of a flat object, an encircling
support 12 (made, for example, of alumina ceramics) for supporting
the flat object supporting area 11 at its circumference, and a
frame fixing area 13 defined on the outer circumference of the
encircling support 12.
[0051] The flat object supporting area 11 is formed by a porous
member such as porous ceramic, allowing air to pass therethrough to
hold the flat object. The flat object supporting area 11 is about 5
mm thick, capable of stably holding thin objects whose thickness is
several tens .mu.m.
[0052] The frame fixing area 13 has a magnet embedded in its
fastening section 13a for attracting a metal frame 15 (see FIG. 3).
The fastening section 13a may have a double-sided adhesive tape,
glue, or a dip applied thereto to fixedly hold the overlying frame
15. The fastening section 13a has through holes 14 made therein,
thereby permitting a pin-like tool (not shown) to push in a
selected through hole for raising the overlying frame.
[0053] Referring to FIG. 2, the flat object supporting area 11 is
thicker than the frame fixing area 13, the top surface of which
remains at a level lower than the top surface of the flat object
supporting area 11.
[0054] A flat object such as a semiconductor wafer W is put on an
adhesive protection tape 16 as shown in FIG. 3, which is applied to
the rear side of the ring-like frame 15. Thus, the semiconductor
wafer W is integrally connected to the frame 15 via the protection
tape 16.
[0055] Referring to FIG. 4, the ring-like frame 15 has an opening
17 for accommodating a flat object and a front side 18, and the
rear side 19 of the frame 15 is used as a tape applying area, which
encircles the opening 17. As shown in FIG. 3, the protection tape
16 is applied to the rear side (tape applying area) 19 to dose the
opening 17.
[0056] Referring to FIG. 5, the semiconductor wafer-and-frame
assembly is laid on the flat-object holder 10 with the protection
tape 16 lying between the semiconductor wafer W and the flat object
supporting area 11, and with the frame 15 fixedly laid on the frame
fixing area 13. The frame 15 is magnetically attracted to the frame
fixing area 13. In this position, the rear side of the
semiconductor wafer W is at a level higher than the upper surface
of the frame 15, or is almost flush therewith.
[0057] A plurality of semiconductor wafers W each integrally
combined with the flat-object holder 10 via the protection tape 16
are put in a container 21, which is associated with a grinding
machine 20.
[0058] A transferring mechanism 22 transports wafer-and-frame
assemblies one after another from the container 21 to a positioning
device 23. Then, a first transport device 24 transfers
wafer-and-frame assemblies one after another from the positioning
device 23 to a selected chuck table 25.
[0059] Referring to FIG. 7, the chuck table 25 comprises a porous
suction area 25a made of porous ceramic material permitting air to
pass therethrough, and an annular frame body 25b supporting the
suction area 25a by the outer circumference of suction area 25a. A
suction source (not shown) is connected to the lower surface of the
suction area 25a so that the flat-object holder 10 may be held
stably by applying a negative pressure to the suction area 25a.
Likewise, the protection tape T is sucked and pulled onto the flat
object supporting area 11. Therefore, the wafer W is held stably.
Each of the other chuck tables 26 and 27 is constructed
similarly.
[0060] Referring to FIG. 6 again, every chuck table 25, 26 or 27 is
rotatable, and can be displaced by a turntable 28. Specifically,
every time the turntable 28 is rotated a predetermined angle (120
degrees in this particular example) counterclockwise, two of the
three chuck tables can be put under a first and second grinding
device 30 and 40.
[0061] As shown, the first grinding device 30 is fastened onto a
movable support 34, which rides on two parallel rails 32 laid on
the upright wall 31 of the grinding machine, and the movable
support 34 can be moved vertically along the upright wall 31 by a
drive source 33. The first grinding device 30 comprises a rotary
spindle 35, a mount 36 fixed to the tip of the rotary spindle 35, a
grinding wheel 37 fixed to the mount 36, and a coarse grindstone 38
attached to the grinding wheel 37.
[0062] Referring to FIG. 8, the rear side of the semiconductor
wafer W is coarse-ground by rotating and lowering the rotary
spindle 35 of the first grinding device 30. The frame fixing area
13 is at a level lower than the flat-object holder 11 so that the
grindstone 38 cannot abut the frame 15.
[0063] When the turntable 28 rotates 120 degrees counterclockwise,
the coarse-ground wafer W is put under the second grinding device
40.
[0064] The second grinding device 40 is fastened onto a movable
support 43, which rides on two parallel rails 41 laid on the
upright wall 31, and the movable support 43 can be moved up and
down on the upright wall 31. The second grinding device 40
comprises a rotary spindle 44, a mount 45 fixed to the tip of the
rotary spindle 44, a grinding wheel 46 fixed to the mount 45, and a
fine grindstone 47 attached to the grinding wheel 46.
[0065] The rear side of the semiconductor wafer W just below the
second grinding device 40 is fine-ground by rotating and lowering
the rotary spindle 44 of the second grinding device 40 to keep
contact with the rear side of the semiconductor wafer W.
[0066] After fine-grinding, the semiconductor wafer W is
transferred to a washing station 49, where debris is removed from
the fine-ground semiconductor wafer W, and the clean semiconductor
wafer W is put in a container 50 with the aid of the transferring
mechanism 22.
[0067] The wafer-and-frame assembly can be easily removed from the
flat-object holder 10 by inserting a pin-like tool in a selected
through-hole 14 and by thrusting the wafer-and-frame assembly
upward. The protection tape 16 is flexible enough to be peeled off
the very thin wafer W without difficulty at the final stage.
[0068] The semiconductor wafer W can be held stably by the
flat-object holder 10 all the time while being displaced and ground
in the grinding machine and when being transferred from the turn
table to the container 50, even though the semiconductor wafer W is
ground to be 100 or less .mu.m thick, or 50 or less .mu.m
thick.
[0069] The supporting of the wafer-and-frame assembly by the
flat-object holder 10 makes it unnecessary to redesign or modify
the chuck tables 25, 26 and 27, which otherwise, would have to be
redesigned or modified to hold the wafer-and-frame by its frame
15.
[0070] Referring to FIG. 9, a flat-object holder 60 according to a
second embodiment comprises a flat object supporting area 61 and an
encircling support 62, the outer peripheral side of which defines
an outer tape-pinching surface 63a. The flat object supporting area
61 is made of a porous ceramic material, and is about 5 mm thick to
support a several tens micron-thick object.
[0071] The support 62 encircles the flat object supporting area 61,
and its major surface is inclined downward from the circumference
of the flat object supporting area 61 to the frame fixing area 63,
which has the outer tape-pinching surface 63a. Thus, the frame
fixing area 63 is at a level lower than the upper surface of the
flat object supporting area 61.
[0072] Referring to FIG. 10, a semiconductor wafer W to be
supported by the flat-object holder 60 is combined with a ring-like
frame 64 via an associated adhesive protection tape 65, which is
applied to the rear side of the ring 64.
[0073] Referring to FIG. 11, the ring-like frame 64 has an opening
66 large enough to accommodate snugly accommodate the semiconductor
wafer W. The inner circumference of the ring 64 is referred to as
"inner supporting surface" 68, and is somewhat larger than the
outer tape-pinching surface 63a in diameter.
[0074] Referring to FIG. 12, the flat-object holder 60 is fitted in
the ring-like frame 64 with the outer tape-pinching surface 63a
facing the inner supporting surface 68, and the semiconductor wafer
W is put on the flat object supporting area 61.
[0075] Referring to FIG. 13, the flat-object holder 60 bearing the
wafer-and-frame assembly is put on the chuck table 25 so that the
semiconductor wafer W may be fixedly held by applying a negative
pressure to the suction area 25a of the chuck table 25. Thus, the
semiconductor wafer W is fixedly held by the chuck table 25 while
being ground in the grinding machine as shown in FIG. 6, and the
wafer-and-frame assembly can be put in the container 50 easily even
though the semiconductor wafer W is ground to be very thin.
[0076] When put in the container 50, each wafer-and-frame assembly
can be removed from the flat-object holder easily because no
suction force is applied. The protection tape 65 is flexible enough
to allow the semiconductor wafer W of reduced thickness to be
removed from the protection tape T without difficulty.
[0077] Thanks to the supporting of the tape-and-frame combination
by the flat-object holder 60, the chuck table 25, 26 or 27 need not
be redesigned or modified to support the frame 64.
[0078] In this particular embodiment, the flat object supporting
area and the encircling support are constructed so as to be
separate. However, these can be constructed as a whole with a
porous body and coated with fluorine or titanium oxide at the area
corresponding to the encircling support.
[0079] The semiconductor wafer is one example of flat object. Other
examples include a rearranged, rewired semiconductor substrate like
a flip chip and a rearranged, rewired and resin-sealed
semiconductor substrate like a CSP substrate.
[0080] One example of using a flat-object holder 60 when grinding
the rear side of a semiconductor wafer W to dice the ground
semiconductor wafer is described below, beginning with the
application of a dicing tape to the semiconductor wafer and ending
with removal of the flat-object holder 60.
[0081] As is well known, the semiconductor wafer W is ground on its
rear side to be divided into squares, and each semiconductor chip
is wire-bonded at a later stage. A die-attachment film, however,
needs to be applied to the rear side of the semiconductor wafer
prior to the wire-bonding.
[0082] As seen from FIG. 14(B), a die-attachment film 100 is
applied to the rear side of the post-grinding semiconductor wafer
W, which is fixedly held by the flat-object holder 60 with the
frame 64 of the wafer-and-frame assembly tightly fitted on the
outer circumference of the flat-object holder 60 (see FIG.
14(A)).
[0083] Specifically the flat-object holder 60 bearing the
semiconductor wafer W is put on the table 101 of a mount device to
heat the semiconductor wafer to a temperature ranging from
100.degree. to 150.degree., and then the die-attachment film 100 is
applied to the rear side of the semiconductor wafer W by pushing it
against the semiconductor wafer W with a roll 102 while the
semiconductor wafer W is being fixedly supported by the flat-object
holder 60 by applying a negative pressure to the table 101.
[0084] As seen from FIG. 14(C), the die-attachment film 100 is cut
around or on the circumference of the frame 64 (see FIG. 14(D)).
The heating of the cutter 103 to a temperature ranging from
40.degree. to 60.degree. facilitates the required cutting.
[0085] The die-attachment film 100 is applied to not only the
semiconductor wafer W but also the frame 64, which can be easily
separated from the die-attachment film 100 by lowering the
temperature of the die-attachment film 100 when removing the frame
64 as described later.
[0086] Referring to FIG. 14(E), the flat-object holder 60 is put on
the table 105 of a tape-applying device to apply a dicing tape 104
onto the die-attachment film 100. The semiconductor wafer W is
fixedly held on the table 105 via the flat object supporting area
61 by applying a negative pressure to the rear side of the table
105. The dicing tape 104 is applied to the underlying
die-attachment film 100 with a roll 107, and then, the cutter 108
is used to cut the dicing tape 104 on the dicing frame 106.
[0087] Referring to FIG. 14(F), the semiconductor wafer W having
the underlying die-attachment film 100 and the overlying dicing
tape 104 applied to its front side, and the flat-object holder 60
having the frame 64 fitted on its outer circumference, are combined
as a whole to be turned upside down. The combination is laid on the
table 109 of a removal device with the semiconductor wafer W facing
downward. The semiconductor wafer is fixedly held on the table 109
via the dicing tape 104 by applying a negative pressure to the rear
side of the table 109. The table is preferably made of a porous
material to permit suction of the whole area of the semiconductor
wafer.
[0088] Referring to FIG. 14(G), the frame 64 is raised and removed
with the aid of a robot hand or of a magnet when the frame is made
of a metal to be magnetically attracted. The frame 64 has the
die-attachment film 100 applied thereto. The die-attachment film
100 is lowered to a normal temperature, permitting easy removal of
the frame 64 from the die-attachment film 100.
[0089] Referring to FIG. 14(H), when the frame 64 is raised and
removed from the flat-object holder 60, a small amount of air is
made to blow downward from the flat-object holder 60 to facilitate
removal of the flat-object holder 60 from the semiconductor wafer
W.
[0090] The protection tape 65 is removed subsequent to removal of
the flat-object holder 60. If the protection tape is responsive to
ultraviolet rays for hardening, the protection tape 65 is exposed
to ultraviolet rays beforehand, thereby lowering the adhesive power
of the protection tape 65 to facilitate the peeling-off of the
protection tape 65, as seen in FIG. 14(I).
[0091] The protection tape 65 is applied to the whole area of the
flat-object holder 60, and therefore, it extends beyond the outer
circumference of the semiconductor wafer W The marginal extension
of protection tape 65 beyond the outer circumference of the
semiconductor wafer is caught by the robot hand 110 to peel off the
semiconductor wafer, which is fixedly held on the table 109 via the
dicing tape 104, as seen in FIGS. 14(J) and 14(K).
[0092] Hitherto, the protection tape 65 has been as large as the
semiconductor wafer W and, therefore, an extra tape has been used
only for the purpose of peeling the protection tape 65 off the
semiconductor wafer. In contrast, the protection tape 65 has a
marginal circumference to be caught (grabbed), thereby facilitating
the peeling of the protection tape 65 off the semiconductor
wafer.
[0093] Thus, the semiconductor wafer is integrally combined with
the dicing frame 106 via the dicing tape 104, so that the
semiconductor wafer may be diced immediately.
[0094] If the dicing work follows the grinding of a semiconductor
wafer on its rear side (the wafer being fixedly held by a
flat-object holder 60), described below is the second example of a
process beginning with application of a die-attachment film 100 to
the semiconductor wafer and ending with removal of the protection
tape 65.
[0095] The steps shown in FIGS. 15(A) to 15(F) correspond to those
in FIGS. 14(A) to 14(F), although the frame 111 encircling the
flat-object holder 60 is made of a metal, and is expandable.
[0096] Referring to FIG. 16, the expandable frame 111 is composed
of a ring-like steel spring 113 having thumb catches 112 formed at
its loop-ends. The expandable frame 111 increases its size as the
opposite thumb catches 112 get close to each other whereas the
expandable frame 111 decreases its size as the opposite thumb
catches 112 separate from each other. The position in which the
steel spring ring 113 tightly encircles the flat-object holder 60
is called the "pinching condition," whereas the position in which
the steel spring ring 113 loosely encircles the flat-object holder
60, leaving a small gap therebetween, is called the"releasing
condition".
[0097] Referring to FIG. 15(G), after the flat-object holder 60 is
turned upside down, the expandable frame 111 is put in the
releasing condition, still allowing the ring 111 to remain around
the flat-object holder 60.
[0098] Referring to FIG. 15(H), the flat-object holder 60 is raised
with a robot hand while a small amount of air is blown from the
flat-object holder 60 to facilitate removal of the semiconductor
wafer W from the flat-object holder 60.
[0099] Referring to FIG. 15(I), the ultraviolet-sensitive
protection tape 65 is exposed to ultraviolet rays for hardening and
lowering its adhesive power. Then, the marginal area of the
protection tape 65 is caught (grabbed) by the robot hand 114 to
peel the protection tape 65 off the semiconductor wafer W, which is
fixedly held on the table 109 with the dicing tape 104 laid
therebetween.
[0100] Here it should be noted that the semiconductor wafer W is
fixedly held on the table 109 by allowing the frame 111 to push the
semiconductor wafer W against the table 109 via the die-attachment
film 100 and the dicing tape 104, which film and tape have the
effect of preventing the semiconductor wafer W from being rolled up
forcedly to be broken when the protection tape 65 is peeled off the
semiconductor wafer W.
[0101] Referring to FIG. 15(L), finally, the expanded frame 111 is
removed, leaving the semiconductor wafer W integrally combined with
the dicing frame 109, and the combined semiconductor wafer W can be
transferred to the dicing station.
[0102] Referring to FIG. 17, a flat-object holder 120 is designed
to be laid on others in the form of a stack. It comprises a flat
object supporting area 121 and a support 127 encircling the flat
object supporting area 121. The support 127 has a tape pinching
area 125a on its outer circumference 125 to cooperate with the
inner tape-pinching circumference area of the frame 126 for
pinching the outer marginal circumference of the protection tape
therebetween.
[0103] The support 127 is an annular body whose outer front side
diverges downward to form a bearing shoulder 123, and the oblique
front side ends with the vertical outer circumference 125. The
support 127 has an inner rear side diverging from the circumference
of the circular opening to the lower edge of the vertical outer
circumference 125 to form a landing seat 124. The flat-object
holder 120 has a recess 122 on its bottom to accommodate the flat
object of the lower flat-object holder in a non-contact fashion
when two or more flat-object holders are laid on each other, as
seen from FIG. 18. The bearing shoulder 123 of the lower
flat-object holder abuts the landing seat 124 of the upper
flat-object holder for bearing the upper flat-object holder.
[0104] Thus, there is no fear of damaging semiconductor wafers when
stacking. Therefore, stacks of semiconductor wafers can be
transferred from place to place without using such containers 21,
50 as shown in FIG. 6. Accordingly, the expense involved for
containing such fragile objects in appropriate containers and for
allotting extra spaces for such containers can be saved.
[0105] A flat-object holder capable of heating a flat object is
described below. It is necessary that semiconductor wafers be
heated when certain kinds of protection tape 65, die-attachment
film 100 and dicing tape 104 are applied to the semiconductor
wafers. Hitherto, machines or apparatuses used have been equipped
with a heating means, which can heat the semiconductor wafer laid
on a jig which permits heat conduction from the heating means to
the semiconductor wafer.
[0106] Heating a very thin semiconductor wafer is apt to induce
cracking of the wafer due to uneven thermal expansion. This
unfavorable tendency will be noticeable when use is made of a
die-attachment film requiring heating in a temperature ranging from
100.degree. to 1500.degree.. The cracking cannot be prevented
unless the heating of the semiconductor wafer is locally
controlled.
[0107] In an attempt to reduce such a defect, a length of electric
heating wire is arranged and embedded in the flat-object holder 60
or 120 to form a geometrical heating pattern according to which the
heating can be gradually expanded while suppressing the cracking of
the wafer and while continuing to apply the die-attachment film to
the wafer.
[0108] Referring to FIGS. 19, 20 and 21, the flat-object-holders
130, 131 and 132 have different geometrical patterns of electric
heating wire embedded in their flat object supporting areas. Each
flat-object holder has one or more pairs of contact terminals 136
to locally supply the electric heating wire with electricity.
Preferably, the machine or apparatus is constructed so that it may
have counter contact terminals to mate with the contact terminals
of the flat-object holder when it is set on the machine or
apparatus.
[0109] Referring to FIG. 22, a fat-object holder 140 has a conduit
141 formed in its flat object supporting area, thereby permitting a
thermal medium to circulate in the flat object supporting area.
Such thermal medium includes liquid natrium at an elevated
temperature and liquid nitrogen at a low temperature. When grinding
a semiconductor wafer W, the cooling is necessary to suppress the
rise of temperature caused by friction, whereas when applying a
die-attachment film to the semiconductor wafer W, the heating is
necessary to soften the die-attachment film.
[0110] When removing the flat-object holder 140, it is heated to
thermally expand, thereby facilitating removal of the flat-object
holder 140 from the grinding machine.
[0111] Alternatively, a Peltier element may be embedded in the flat
object supporting area, so that the temperature of the flat object
supporting area may be controlled to cool or heat the overlying
semiconductor wafer by controlling the voltage applied to the
Peltier element.
[0112] Referring to FIG. 23, the flat-object holder 150 has an
identification means in the form of bar codes 151 on its rear side,
so that manufacturing management may be facilitated when
transferring semiconductor wafers from station to station for
different treatments, which must be performed at the right position
and situation established in consideration of pieces of information
representing the conditions of semi-products and machining
apparatuses.
[0113] Another example of an identification means is IC chips 161
and 171 on the flat-object holders 160 and 170 (see FIGS. 24 and
25). Writing-in and reading-out of pieces of information are
permitted in IC chips, thus providing the flat-object holder with
traceability.
[0114] When grinding a semiconductor wafer to a desired thickness,
the removal amount of semiconductor material is determined in terms
of how high the ground surface of the semiconductor wafer is from
the reference level at which the suction surface of the chuck table
is, which reference level is measured by a height gauge. If a
semiconductor wafer is laid on a flat-object holder, and the
flat-object holder is put on a selected chuck table, the removal
amount of semiconductor material depends on the height of the
flat-object holder, which varies with each flat-object holder.
Therefore, the removal amount of semiconductor material cannot be
determined accurately without measuring the height of an individual
flat-object holder.
[0115] Each and every flat-object holder is measured in thickness,
and the measured thickness is given to the flat-object holder, for
instance, in the form of bar codes. In grinding the semiconductor
wafer, a piece of information representing the thickness of the
flat-object holder is retrieved from the bar code to determine the
required removal amount of semiconductor material for each
wafer-and-holder assembly. Thus, when the wafer-and-holder is
changed to grind a new semiconductor wafer, the reference level
need not be readjusted in height. Accordingly, the grinding work
can be effected with an increased efficiency and accuracy.
[0116] The quantity of resistance to the peeling-off of the
protection tape from the semiconductor wafer and other pieces of
information in different processes can be recorded and used in
combination with wafer identifications, lot information and other
data in a data server, thereby permitting required data to be
available in fulfilling all necessary controls according to the
processing schedule.
[0117] FIG. 26 shows a process-management system 180. As shown in
the drawing, wafer identifications, lot numbers, thickness of
protection tapes and other data are transferred to the data server
181. At the same time, semiconductor wafers are transferred to the
wafer-thickness gauge 182 to determine the thickness of each and
every semiconductor wafer, which is stored in the data server 181
in terms of each wafer identification and lot number so that the
operator at each terminal 183 may identify each semiconductor wafer
in terms of its physical characteristics.
[0118] Flat-object holders are fed from the holder feeder 184 to
the holder thickness gauge 185 to measure the thickness of each
flat-object holder, and a bar code representing the measured
thickness of the flat-object holder is applied to the rear side of
the flat-object holder. The bar code reader 186 reads the bar code
to transfer the retrieved data to the data server 181.
[0119] The protection tape feeder 188 feeds protection tapes to the
laminator 187 one after another, and a protection tape is applied
to the front side of each semiconductor wafer. Then the
wafer-and-holder assembly is transferred to the grinding means
189.
[0120] After grinding the rear side of the semiconductor wafer
using the grinding means 189, the flat-object holder 190 is removed
from the wafer-and-frame assembly by the remover means 190. The
wafer-free holder can be identified in terms of its bar code to be
used again for grinding another semiconductor wafer without
measuring the thickness of the flat-object holder.
[0121] As may be understood from the above, a lot of flat-object
holders can be handled in terms of their identification data and
other particulars available from the data server 181 to grind all
semiconductor wafers to a desired thickness by removing the exact
removal amount of semiconductor material.
[0122] As may be apparent from the above, a flat-object holder
according to the present invention can fixedly hold a flat
object-and-frame assembly. Therefore, no matter how thin the flat
object may be, it can be held in such a stable condition that the
very thin object may be transferred, put in a container, and peeled
off without difficulty.
[0123] Advantageously, the wafer-and-holder assembly can be put on
a selected chuck table without the necessity of modifying the chuck
table.
* * * * *