U.S. patent application number 09/211875 was filed with the patent office on 2002-01-03 for wafer bonding method, appartus and vacuum chuck.
Invention is credited to TAKISAWA, TORU, YAMAGATA, KENJI, YONEHARA, TAKAO.
Application Number | 20020001920 09/211875 |
Document ID | / |
Family ID | 26581183 |
Filed Date | 2002-01-03 |
United States Patent
Application |
20020001920 |
Kind Code |
A1 |
TAKISAWA, TORU ; et
al. |
January 3, 2002 |
WAFER BONDING METHOD, APPARTUS AND VACUUM CHUCK
Abstract
Two wafers are properly brought into contact with each other.
The first wafer is supported by a wafer support table (3) having an
annular peripheral portion (3d). The substrate support table (3) is
in contact with only the peripheral portion (3d) of the first
wafer. While the second wafer opposing the first wafer is
supported, the lower surface of the second wafer is pressed near
its central portion, so the first and second wafers come into
contact with each other outward from the central portion. The
central portion (3c) of the wafer support table (3) is not in
contact with the first wafer. Even when particles adhere to the
central portion, unevenness on the supported first wafer can be
prevented. Therefore, no gas is left between the wafers. This
invention also provides a wafer support table formed by fabricating
a silicon wafer. A commercially available silicon wafer is
fabricated by lithography to prepare a wafer support table (31).
The wafer support table (31) has sealing portions (31a, 31b) and
deflection prevention portions (31c). The wafer to be supported is
chucked by reducing the pressure between the sealing portions (31a,
31b). The wafer to be supported is in contact only with the sealing
portions (31a, 31b) and the deflection prevention portions
(31c).
Inventors: |
TAKISAWA, TORU; (ATSUGI-SHI,
JP) ; YONEHARA, TAKAO; (ATSUGI-SHI, JP) ;
YAMAGATA, KENJI; (SAGAMIHARA-SHI, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN
345 PARK AVENUE
NEW YORK
NY
10154
|
Family ID: |
26581183 |
Appl. No.: |
09/211875 |
Filed: |
December 15, 1998 |
Current U.S.
Class: |
438/455 ;
156/581 |
Current CPC
Class: |
H01L 21/6838 20130101;
H01L 21/67092 20130101 |
Class at
Publication: |
438/455 ;
156/581 |
International
Class: |
H01L 021/30; B32B
031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 1997 |
JP |
9-361011 |
Dec 26, 1997 |
JP |
9-361010 |
Claims
What is claimed is:
1. A substrate processing apparatus for overlaying two substrates
and bringing the substrates into contact with each other
comprising: support means for supporting the first substrate; and
pressing means for pressing the second substrate against the first
substrate, the second substrate opposing the first substrate
supported by said support means, wherein said support means has a
support member contacting a peripheral portion of one surface of
the first substrate to support the first substrate.
2. The apparatus according to claim 1, wherein said support means
has chuck means for chucking the first substrate on said support
member.
3. The apparatus according to claim 2, wherein said chuck means has
an annular groove on a surface of said support member, and the
first substrate is chucked by said support member by reducing a
pressure in the groove.
4. The apparatus according to claim 1, wherein said support member
has an annular shape.
5. The apparatus according to claim 1, wherein said support member
supports an outermost portion of one surface of the first
substrate.
6. The apparatus according to claim 1, wherein said pressing means
presses the second substrate substantially at a central portion
thereof.
7. The apparatus according to claim 1, wherein said support means
has, inside said support member, a deflection prevention member for
preventing deflection of the first substrate.
8. The apparatus according to claim 7, wherein said deflection
prevention member supports the first substrate substantially at a
central portion thereof, thereby preventing deflection of the first
substrate.
9. The apparatus according to claim 7, wherein a portion where said
support member is in contact with the first substrate and a portion
where said deflection prevention member is in contact with the
first substrate are positioned substantially in the same plane.
10. The apparatus according to claim 1, wherein the apparatus
further comprises substrate manipulation means for canceling
support of the second substrate after the second substrate is
supported to oppose the first substrate supported by said support
means, and said pressing means presses the second substrate in
synchronism with cancel of support of the second substrate by said
substrate manipulation means.
11. The apparatus according to claim 10, wherein said support means
substantially horizontally supports the first substrate, and said
substrate manipulation means substantially horizontally supports
the second substrate above the first substrate and then cancels
support of the second substrate.
12. A substrate support apparatus for supporting one of two
substrates to be overlaid and brought into contact with each other
comprising: a support member contacting a peripheral portion of one
surface of a substrate to support the substrate.
13. The apparatus according to claim 12 further comprising chuck
means for chucking the substrate on said support member.
14. The apparatus according to claim 13, wherein said chuck means
has an annular groove on a surface of said support member, and the
substrate is chucked by said support member by reducing a pressure
in the groove.
15. The apparatus according to claim 12, wherein said support
member has an annular shape.
16. The apparatus according to claim 12 further comprising, inside
said support member, a deflection prevention member for preventing
deflection of the substrate.
17. The apparatus according to claim 16, wherein said deflection
prevention member supports the substrate substantially at a central
portion thereof, thereby preventing deflection of the
substrate.
18. The apparatus according to claim 16, wherein a portion where
said support member is in contact with the substrate and a portion
where said deflection prevention member is in contact with the
substrate are positioned substantially in the same plane.
19. A substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other comprising:
supporting a first substrate by a support member contacting a
peripheral portion of one surface of the first substrate, and
pressing a second substrate toward the first substrate, the second
substrate opposing the first substrate, thereby bringing the first
and second substrates into contact with each other.
20. The method according to claim 19, wherein a support member
having a chuck mechanism is used as the support member.
21. The method according to claim 19, wherein an annular support
member is used as the support member.
22. The method according to claim 19, wherein the support member
supports an outermost portion of the first substrate.
23. The method according to claim 19, wherein the second substrate
is pressed substantially at a central portion thereof.
24. The method according to claim 19, wherein the step of pressing
the second substrate comprises bringing a deflection prevention
member formed inside the support member into contact with the first
substrate.
25. A substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other comprising the
steps of: transferring first and second substrates to the substrate
processing apparatus of claim 1, overlaying the first and second
substrates and bringing the substrates into contact with each other
by the substrate processing apparatus; and receiving the substrates
in contact with each other from the substrate processing
apparatus.
26. A substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other comprising the
steps of: causing the substrate support apparatus of claim 12 to
support a first substrate; opposing a second substrate to the first
substrate supported by the substrate support apparatus; and
overlaying the first substrate and the second substrate and
bringing the substrates into contact with each other.
27. A method of manufacturing a substrate comprising the steps of:
preparing first and second substrates; and bringing the first and
second substrates into contact with each other by the substrate
processing method of claim 19.
28. A method of manufacturing an SOI substrate comprising the steps
of: preparing first and second substrates; bringing the first and
second substrates into contact with each other by the substrate
processing method of claim 19 to prepare a substrate having a layer
in which a single-crystalline Si layer and an insulating layer are
stacked; and separating the substrates which are in contact with
each other at a portion other than a contact interface to prepare
one of the separated substrates as the substrate having the
single-crystalline Si layer on the insulating layer.
29. A substrate support table comprising a member consisting of a
silicon material.
30. A substrate support table comprising a member-formed from a
silicon wafer.
31. The table according to claim 30 further comprising a chuck
portion for chucking a substrate to be supported.
32. The table according to claim 31, wherein said chuck portion is
formed by lithography.
33. The table according to claim 31, wherein said chuck portion is
formed by etching the silicon wafer.
34. The table according to claim 31, wherein said chuck portion is
formed by wet-etching the silicon wafer.
35. The table according to claim 32, wherein said chuck portion
includes sealing portions for vacuum-chucking the substrate and a
suction hole for exhausting a gas in a space defined by said
sealing portions.
36. The table according to claim 35, wherein said sealing portions
are doubled along inside a periphery of the substrate to be
supported, and the suction hole communicates with the space between
said doubled sealing portions.
37. The table according to claim 35, wherein said sealing portions
project to have a bank shape at the periphery.
38. The table according to claim 37, wherein in chucking the
substrate, only said sealing portions are brought into contact with
the substrate.
39. The table according to claim 35 further comprising a deflection
prevention portion for preventing the chucked substrate from
deflecting.
40. The table according to claim 39, wherein said deflection
prevention portion is formed between said sealing portions.
41. The table according to claim 39, wherein in chucking the
substrate, only said sealing portions and said deflection
prevention portion are brought into contact with the substrate.
42. The table according to claim 39, wherein surfaces of said
sealing portions and said deflection prevention portion, which are
in contact with the substrate to be supported, are positioned
substantially in the same plane.
43. The table according to claim 31, wherein said chuck portion is
located at a position where a peripheral portion of the substrate
to be supported can be chucked.
44. The table according to claim 30, wherein a pin hole through
which a load pin for vertically moving the substrate to be
supported on said substrate support table is inserted extends
through the main body.
45. The table according to claim 30, wherein the silicon wafer
complies with the SEMI standard or the JAIDA standard.
46. A substrate processing apparatus comprising: a substrate
support table of claim 29, wherein a substrate supported by said
substrate support table is processed.
47. A substrate processing apparatus for overlaying two substrates
and bringing the substrates into contact with each other
comprising: an attachment/detachment mechanism for
attaching/detaching said substrate support table of claim 29; and
pressing means for pressing a second substrate toward a first
substrate supported by said attached substrate support table, the
second substrate opposing the first substrate.
48. The apparatus according to claim 47, wherein said pressing
means presses the second substrate substantially at a central
portion thereof.
49. The apparatus according to claim 47, wherein said apparatus
further comprises substrate manipulation means for canceling
support of the second substrate after the second substrate is
supported to oppose the first substrate supported by said substrate
support table, and said pressing means presses the second substrate
in synchronism with cancel of support of the second substrate by
said substrate manipulation means.
50. The apparatus according to claim 49, wherein said substrate
support table substantially horizontally supports the first
substrate, and said substrate manipulation means substantially
horizontally supports the second substrate above the first
substrate and then cancels support of the second substrate.
51. A substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other comprising the
steps of: causing the substrate support table of claim 29 to
support a first substrate; opposing a second substrate to the first
substrate supported by the substrate support table; and overlaying
the first substrate and the second substrate and bringing the
substrates into contact with each other.
52. A substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other comprising the
steps of: transferring first and second substrates to the substrate
processing apparatus of claim 46; overlaying the first and second
substrates and bringing the substrates into contact with each other
by the substrate processing apparatus; and receiving the substrates
in contact with each other from the substrate processing
apparatus.
53. A method of manufacturing an SOI substrate comprising the steps
of: preparing first and second substrates; bringing the first and
second substrates into contact with each other by the substrate
processing method of claim 51 to prepare a substrate having a layer
in which a single-crystalline Si layer and an insulating layer are
stacked; and separating the substrates which are in contact with
each other at a portion other than a contact interface to prepare
one of the separated substrates as the substrate having the
single-crystalline Si layer on the insulating layer.
54. A cleaning method comprising: cleaning the substrate support
table while accommodating the substrate support table of claim 29
in a wafer cassette for storing a wafer for manufacturing a
semiconductor device.
55. A method of handling the wafer processing apparatus of claim 46
comprising the steps of: detaching the substrate support table from
the wafer processing apparatus; cleaning the substrate support
table while accommodating the detached substrate support table in a
wafer cassette for storing a wafer for manufacturing a
semiconductor device; and attaching the cleaned substrate support
table in the wafer processing apparatus.
56. A method of manufacturing a substrate support table comprising
the steps of: forming an SiO.sub.2 film to cover an entire silicon
wafer; forming a first photoresist film on one surface of the
SiO.sub.2 film; patterning the first photoresist film to expose the
SiO.sub.2 film at a portion where sealing portions for vacuum
chucking are to be formed; etching the SiO.sub.2 film at the
exposed portion to expose the silicon wafer; removing the remaining
first photoresist film; etching the silicon wafer at the exposed
portion to a predetermined depth; forming an SiO.sub.2 film to
cover the entire silicon wafer; forming a second photoresist film
on the other surface of the SiO.sub.2 film; patterning the second
photoresist film to expose the SiO.sub.2 film at a portion where a
suction hole for vacuum chucking is to be formed; etching the
SiO.sub.2 film at the exposed portion to expose the silicon wafer;
removing the remaining second photoresist film; etching the silicon
wafer at the exposed portion to form the suction hole extending
through the silicon wafer; and removing the remaining SiO.sub.2
film.
57. A method of manufacturing a substrate support table comprising
the steps of: forming a first film to cover an entire silicon
wafer; forming a first photoresist film on one surface of the first
film; patterning the first photoresist film to expose the first
film at a portion where sealing portions for vacuum chucking are to
be formed; etching the first film at the exposed portion to expose
the silicon wafer; removing the remaining first photoresist film;
etching the silicon wafer at the exposed portion to a predetermined
depth; forming a second film to cover the entire silicon wafer;
forming a second photoresist film on the other surface of the
second film; patterning the second photoresist film to expose the
second film at a portion where a suction hole for vacuum chucking
is to be formed; etching the second film at the exposed portion to
expose the silicon wafer; removing the remaining second photoresist
film; etching the silicon wafer at the exposed portion to form the
suction hole extending through the silicon wafer; and removing the
remaining second film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a substrate processing
apparatus for overlaying and contacting two substrates with each
other, a substrate support apparatus, and a substrate processing
method, and a substrate manufacturing method using the apparatus or
method.
[0003] The present invention also relates to a substrate support
table consisting of a silicon material, a substrate processing
apparatus including the substrate support table, methods of
manufacturing and handling the substrate support table, and a
substrate processing method.
[0004] 2. Description of the Related Art
[0005] There is a method of bringing two wafers (substrates) into
contact and bonding them by anode bonding, pressing, or heat
treatment. This method is suitable to manufacture a wafer having,
e.g., an SOI structure.
[0006] FIGS. 14A and 14B are schematic views showing the step of
bonding wafers. In this bonding step, first, a first wafer 1 with
its bonding surface facing up is set on a wafer support jig 201,
and a second wafer 2 with its bonding surface facing down is softly
placed on the first wafer 1, as shown in FIG. 14A. At this time,
the upper wafer 2 floats on the gas (e.g., air or an inert gas)
between the wafers, as shown in FIG. 14A.
[0007] As shown in FIG. 14B, when a press pin 202 presses the upper
wafer 2 near its central portion before the gas between the wafers
1 and 2 is completely removed, the air at the central portion of
the wafers moves to the periphery. The wafers 1 and 2 come into
contact with each other at the central portion first. As the gas
between the wafers gradually moves outward, the contact area
expands, and finally, the entire wafers come contact with each
other.
[0008] Although the above method is applicable to bring two wafers
into contact by simple operation, it has the following
problems.
[0009] One of the problems is associated with wafer contamination
due to alignment of two wafers. Since the upper wafer 2 floats on
the gas between the wafers, friction in moving the upper wafer 2 in
the horizontal plane is very small. The upper wafer 2 slides even
when the jig 201 slightly tilts. Therefore, to properly align the
two wafers 1 and 2, a means for limiting movement of the wafer 2 in
the horizontal plane is required.
[0010] The jig 201 shown in FIGS. 14A and 14B has a recessed
portion conforming to the shape of the wafers 1 and 2. The wafers 1
and 2 are aligned while being limited in their movement in the
horizontal direction by the side walls of the recessed portion.
[0011] FIG. 15 is a view showing another jig for overlaying the
wafers 1 and 2 while aligning them. A jig 203 has a plurality of
alignment pins 204 and a press pin 205. The wafers 1 and 2 are
pressed against the plurality of alignment pins 204 by the press
pin 205, thereby limiting movement of the wafers 1 and 2 in the
horizontal plane.
[0012] The method of overlaying two wafers using the jig shown in
FIGS. 14A and 14B or FIG. 15 has factors that generate particles,
inflict damage to the peripheral portions of the wafers, or lower
the yield because the peripheral portions of the wafers are in
contact with the jig.
[0013] As another problem, no constant condition can be obtained in
pressing the wafers. More specifically, the time after the two
wafers are overlaid until they are pressed by the press pin is not
constant, and the gap between the wafers in pressing them by the
press pin is not constant. Therefore, the quality of the wafer
obtained by bringing two wafers into contact can hardly be
uniformed. In addition, the gas between the wafers sometimes
escapes before the wafers are pressed by the press pin. In this
case, since the wafers cannot be brought into contact while
gradually removing the gas outward from the central portion, some
gas may remain entrapped between the wafers.
[0014] As an apparatus for supporting a substrate to be processed
in the manufacture of a semiconductor device, a substrate support
apparatus for supporting a substrate by vacuum chucking is used. As
a substrate support table, i.e., a unit of the substrate support
apparatus, normally, a plate consisting of a metal or ceramic
material with high rigidity and having a chuck groove is used.
[0015] However, the conventional substrate support table is
expensive in general, and a demand for a more inexpensive substrate
support table has arisen.
SUMMARY OF THE INVENTION
[0016] The present invention has been made in consideration of the
above problems, and has as its object to increase the quality of a
substrate obtained by bringing two substrates into contact with
each other.
[0017] According to the present invention, there is provided a
substrate processing apparatus for overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising support means for supporting the first substrate; and
pressing means for pressing the second substrate against the first
substrate, the second substrate opposing the first substrate
supported by the support means, wherein the support means has a
support member contacting a peripheral portion of one surface of
the first substrate to support the first substrate.
[0018] In the substrate processing apparatus, the support means
preferably has chuck means for chucking the first substrate on the
support member.
[0019] In the substrate processing apparatus, preferably, the chuck
means has an annular groove on a surface of the support member, and
the first substrate is chucked by the support member by reducing a
pressure in the groove.
[0020] In the substrate processing apparatus, the support member
preferably has an annular shape.
[0021] In the substrate processing apparatus, the support member
preferably supports an outermost portion of one surface of the
first substrate.
[0022] In the substrate processing apparatus, the pressing means
preferably presses the second substrate substantially at a central
portion thereof.
[0023] In the substrate processing apparatus, the support means
preferably has, inside the support member, a deflection prevention
member for preventing deflection of the first substrate.
[0024] In the substrate processing apparatus, the deflection
prevention member preferably supports the first substrate
substantially at a central portion thereof, thereby preventing
deflection of the first substrate.
[0025] In the substrate processing apparatus, a portion where the
support member is in contact with the first substrate and a portion
where the deflection prevention member is in contact with the first
substrate are preferably positioned substantially in the same
plane.
[0026] Preferably, the substrate processing apparatus further
comprises substrate manipulation means for canceling support of the
second substrate after the second substrate is supported to oppose
the first substrate supported by the support means, and the
pressing means presses the second substrate in synchronism with
cancel of support of the second substrate by the substrate
manipulation means.
[0027] In the substrate processing apparatus, preferably, the
support means substantially horizontally supports the first
substrate, and the substrate manipulation means substantially
horizontally supports the second substrate above the first
substrate and then cancels support of the second substrate.
[0028] According to the present invention, there is also provided a
substrate support apparatus for supporting one of two substrates to
be overlaid and brought into contact with each other, characterized
by comprising a support member contacting a peripheral portion of
one surface of a substrate to support the substrate.
[0029] The substrate support apparatus preferably further comprises
chuck means for chucking the substrate on the support member.
[0030] In the substrate support apparatus, preferably, the chuck
means has an annular groove on a surface of the support member, and
the substrate is chucked by the support member by reducing a
pressure in the groove.
[0031] In the substrate support apparatus, the support member
preferably has an annular shape.
[0032] The substrate support apparatus preferably further
comprises, inside the support member, a deflection prevention
member for preventing deflection of the substrate.
[0033] In the substrate support apparatus, the deflection
prevention member preferably supports the substrate substantially
at a central portion thereof, thereby preventing deflection of the
substrate.
[0034] In the substrate support apparatus, a portion where the
support member is in contact with the substrate and a portion where
the deflection prevention member is in contact with the substrate
are preferably positioned substantially in the same plane.
[0035] According to the present invention, there is also provided a
substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising supporting a first substrate by a support member
contacting a peripheral portion of one surface of the first
substrate, and pressing a second substrate toward the first
substrate, the second substrate opposing the first substrate,
thereby bringing the first and second substrates into contact with
each other.
[0036] In the substrate processing method, preferably, a support
member having a chuck mechanism is used as the support member.
[0037] In the substrate processing method, preferably, an annular
support member is used as the support member.
[0038] In the substrate processing method, the support member
preferably supports an outermost portion of the first
substrate.
[0039] In the substrate processing method, the second substrate is
preferably pressed substantially at a central portion thereof.
[0040] In the substrate processing method, the step of pressing the
second substrate preferably comprises bringing a deflection
prevention member formed inside the support member into contact
with the first substrate.
[0041] The above apparatus and method are suitable to manufacture a
SOI substrate.
[0042] According to the present invention, there is provided a
substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising the steps of transferring first and second substrates
to any one of the above substrate processing apparatuses,
overlaying the first and second substrates and bringing the
substrates into contact with each other by the substrate processing
apparatus, and receiving the substrates in contact with each other
from the substrate processing apparatus.
[0043] According to the present invention, there is also provided a
substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising the steps of causing any one of the above substrate
support apparatuses to support a first substrate, opposing a second
substrate to the first substrate supported by the substrate support
apparatus, and overlaying the first substrate and the second
substrate and bringing the substrates into contact with each
other.
[0044] According to the present invention, there is also provided a
method of manufacturing a substrate, characterized by comprising
the steps of preparing first and second substrates, and bringing
the first and second substrates into contact with each other by any
one of the above substrate processing methods.
[0045] According to the present invention, there is also provided a
method of manufacturing an SOI substrate, characterized by
comprising the steps of preparing first and second substrates,
bringing the first and second substrates into contact with each
other by any one of the above substrate processing methods to
prepare a substrate having a layer in which a single-crystalline Si
layer and an insulating layer are stacked, and separating the
substrates which are in contact with each other at a portion other
than a contact interface to prepare one of the separated substrates
as the substrate having the single-crystalline Si layer on the
insulating layer.
[0046] The present invention has been made in consideration of the
above problems, and has as its object to provide an inexpensive
substrate support table.
[0047] According to the present invention, there is provided a
substrate support table characterized by comprising a member
consisting of a silicon material.
[0048] According to the present invention, there is also provided a
substrate support table characterized by comprising a member formed
from a silicon wafer.
[0049] The substrate support table preferably comprises a chuck
portion for chucking a substrate to be supported.
[0050] In the substrate support table, the chuck portion is
preferably formed by lithography.
[0051] In the substrate support table, the chuck portion is
preferably formed by etching the silicon wafer.
[0052] In the substrate support table, the chuck portion is
preferably formed by wet-etching the silicon wafer.
[0053] In the substrate support table, the chuck portion preferably
includes sealing portions for vacuum-chucking the substrate and a
suction hole for exhausting a gas in a space defined by the sealing
portions.
[0054] In the substrate support table, preferably, the sealing
portions are doubled along inside a periphery of the substrate to
be supported, and the suction hole communicates with the space
between the doubled sealing portions.
[0055] In the substrate support table, the sealing portions
preferably project to have a bank shape at the periphery.
[0056] In the substrate support table, preferably, in chucking the
substrate, only the sealing portions are brought into contact with
the substrate.
[0057] The substrate support table preferably further comprises a
deflection prevention portion for preventing the chucked substrate
from deflecting.
[0058] In the substrate support table, the deflection prevention
portion is preferably formed between the sealing portions.
[0059] In the substrate support table, preferably, in chucking the
substrate, only the sealing portions and the deflection prevention
portion are brought into contact with the substrate.
[0060] In the substrate support table, the surfaces of the sealing
portions and the deflection prevention portion, which are in
contact with the substrate to be supported, are preferably
positioned substantially in the same plane.
[0061] In the substrate support table, the chuck portion is
preferably located at a position where a peripheral portion of the
substrate to be supported can be chucked.
[0062] In the substrate support table, preferably, a pin hole
through which a load pin for vertically moving the substrate to be
supported on the substrate support table is inserted extends
through the main body.
[0063] The silicon wafer preferably complies with the SEMI standard
or the JAIDA standard.
[0064] According to the present invention, there is provided a
substrate processing apparatus for overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising an attachment/detachment mechanism for
attaching/detaching the substrate support table, and pressing means
for pressing a second substrate toward a first substrate supported
by the attached substrate support table, the second substrate
opposing the first substrate.
[0065] In the substrate processing apparatus, the pressing means
preferably presses the second substrate substantially at a central
portion thereof.
[0066] Preferably, the substrate processing apparatus further
comprises substrate manipulation means for canceling support of the
second substrate after the second substrate is supported to oppose
the first substrate supported by the substrate support table, and
the pressing means presses the second substrate in synchronism with
cancel of support of the second substrate by the substrate
manipulation means.
[0067] In the substrate processing apparatus, preferably, the
substrate support table substantially horizontally supports the
first substrate, and the substrate manipulation means substantially
horizontally supports the second substrate above the first
substrate and then cancels support of the second substrate.
[0068] The above substrate support table and the substrate
processing apparatus are suitable to manufacture, e.g., an SOI
substrate.
[0069] According to the present invention there is provided a
substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising the steps of causing any one of the above substrate
support tables to support a first substrate, opposing a second
substrate to the first substrate supported by the substrate support
table, and overlaying the first substrate and the second substrate
and bringing the substrates into contact with each other.
[0070] According to the present invention, there is also provided a
substrate processing method of overlaying two substrates and
bringing the substrates into contact with each other, characterized
by comprising the steps of transferring first and second substrates
to any one of the above substrate processing apparatuses,
overlaying the first and second substrates and bringing the
substrates into contact with each other by the substrate processing
apparatus, and receiving the substrates in contact with each other
from the substrate processing apparatus.
[0071] According to the present invention, there is also provided a
method of manufacturing an SOI substrate, characterized by
comprising the steps of preparing first and second substrates,
bringing the first and second substrates into contact with each
other by any one of the above substrate processing methods to
prepare a substrate having a layer in which a single-crystalline Si
layer and an insulating layer are stacked, and separating the
substrates which are in contact with each other at a portion other
than a contact interface to prepare one of the separated substrates
as the substrate having the single-crystalline Si layer on the
insulating layer.
[0072] According to the present invention, there is also provided a
cleaning method characterized by comprising cleaning the substrate
support table while accommodating the above substrate support table
in a wafer cassette for storing a wafer for manufacturing a
semiconductor device.
[0073] According to the present invention, there is also provided a
method of handling the wafer processing apparatus, characterized by
comprising the steps of detaching the substrate support table from
the wafer processing apparatus, cleaning the substrate support
table while accommodating the detached substrate support table in a
wafer cassette for storing a wafer for manufacturing a
semiconductor device, and attaching the cleaned substrate support
table in the wafer processing apparatus.
[0074] According to the present invention, there is also provided a
method of manufacturing a substrate support table, characterized by
comprising the steps of forming an SiO.sub.2 film to cover an
entire silicon wafer, forming a first photoresist film on one
surface of the SiO.sub.2 film, patterning the first photoresist
film to expose the SiO.sub.2 film at a portion where sealing
portions for vacuum chucking are to be formed, etching the
SiO.sub.2 film at the exposed portion to expose the silicon wafer,
removing the remaining first photoresist film, etching the silicon
wafer at the exposed portion to a predetermined depth, forming an
SiO.sub.2 film to cover the entire silicon wafer, forming a second
photoresist film on the other surface of the SiO.sub.2 film,
patterning the second photoresist film to expose the SiO.sub.2 film
at a portion where a suction hole for vacuum chucking is to be
formed, etching the SiO.sub.2 film at the exposed portion to expose
the silicon wafer, removing the remaining second photoresist film,
etching the silicon wafer at the exposed portion to form the
suction hole extending through the silicon wafer, and removing the
remaining SiO.sub.2 film.
[0075] According to the present invention, there is also provided a
method of manufacturing a substrate support table, characterized by
comprising the steps of forming a first film to cover an entire
silicon wafer, forming a first photoresist film on one surface of
the first film, patterning the first photoresist film to expose the
first film at a portion where sealing portions for vacuum chucking
are to be formed, etching the first film at the exposed portion to
expose the silicon wafer, removing the remaining first photoresist
film, etching the silicon wafer at the exposed portion to a
predetermined depth, forming a second film to cover the entire
silicon wafer, forming a second photoresist film on the other
surface of the second film, patterning the second photoresist film
to expose the second film at a portion where a suction hole for
vacuum chucking is to be formed, etching the second film at the
exposed portion to expose the silicon wafer, removing the remaining
second photoresist film, etching the silicon wafer at the exposed
portion to form the suction hole extending through the silicon
wafer, and removing the remaining second film.
[0076] Further object, features and advantages of the present
invention will become apparent from the following detailed
description of embodiments of the present invention with reference
to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0077] FIG. 1 is a perspective view schematically showing the
overall arrangement of a wafer processing apparatus according to a
preferred embodiment of the present invention;
[0078] FIG. 2 is an enlarged view of part of FIG. 1;
[0079] FIG. 3 is a sectional view showing the arrangement of a
wafer support section of the wafer processing apparatus shown in
FIGS. 1 and 2;
[0080] FIG. 4 is a view showing a state wherein two wafers are
brought into contact on the wafer support section shown in FIG.
3;
[0081] FIGS. 5 to 9 are sectional views of the wafer processing
apparatus shown in FIGS. 1 and 2 taken along a line A-A';
[0082] FIG. 10 is a block diagram showing the arrangement of the
control system of the wafer processing apparatus;
[0083] FIG. 11 is a flow chart showing the control procedure based
on a program;
[0084] FIG. 12 is a sectional view showing the structure of a wafer
support table according to the second embodiment;
[0085] FIGS. 13A to 13F are views showing steps in manufacturing a
wafer having, e.g., an SOI structure;
[0086] FIGS. 14A and 14B are schematic views showing steps in
bonding wafers;
[0087] FIG. 15 is a view showing an example of a jig for overlaying
two wafers while positioning them;
[0088] FIG. 16 is a plan view showing the arrangement of a wafer
support table according to the third embodiment of the present
invention;
[0089] FIG. 17 is a sectional view of part of the wafer support
table shown in FIG. 16;
[0090] FIG. 18 is a sectional view showing the arrangement of a
wafer support apparatus including the wafer support table shown in
FIG. 16;
[0091] FIGS. 19A to 19N are views showing steps in manufacturing
the wafer support table;
[0092] FIG. 20 is a view showing a state wherein two wafers are
brought into contact using the wafer support apparatus;
[0093] FIG. 21 is a perspective view schematically showing the
overall arrangement of a wafer processing apparatus;
[0094] FIG. 22 is an enlarged view of part of FIG. 21;
[0095] FIGS. 23 to 27 are sectional views of the wafer processing
apparatus shown in FIGS. 21 and 22 taken along a line A-A';
[0096] FIG. 28 is a block diagram showing the arrangement of the
control system of the wafer processing apparatus; and
[0097] FIG. 29 is a flow chart showing the control procedure of
based on a program.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0098] Preferred embodiments of the present invention will be
described below with reference to the accompanying drawings.
First Embodiment
[0099] FIG. 1 is a perspective view schematically showing the
overall arrangement of a wafer processing apparatus according to
the first embodiment. FIG. 2 is an enlarged view of part of FIG. 1.
FIG. 3 is a sectional view showing the arrangement of a wafer
support section of a wafer processing apparatus 100 shown in FIGS.
1 and 2. FIG. 4 is a view showing a state wherein two wafers are
brought into contact on the wafer support section shown in FIG. 3.
FIGS. 5 to 9 are sectional views showing the wafer processing
apparatus 100 show in FIGS. 1 and 2 taken along a line A-A'. FIGS.
5 to 9 show the operation of bringing two wafers into contact.
[0100] The wafer processing apparatus 100 overlays two wafers and
brings them into contact and is suitably used to practice a method
of bonding two wafers to manufacture a wafer having, e.g., an SOI
structure.
[0101] The wafer processing apparatus 100 has a wafer support table
3 for supporting a first wafer 1 (FIG. 4) from its lower surface,
and a wafer moving mechanism 4 for chucking a second wafer 2 (FIG.
4) from its lower surface and making the second wafer 2 oppose
almost parallel to the first wafer 1.
[0102] The wafer support table 3 preferably has a contact surface
which comes into contact with only the peripheral portion (and more
preferably with the outermost portion) of the lower surface of the
first wafer 1. The contact surface is preferably annular. When the
wafer support table 3 comes into contact with only the lower
surface of the first wafer 1, the upper surface of the first wafer
1 can be prevented from being contaminated by particles, and
additionally, damage to the first wafer 1 can also be prevented.
Furthermore, when the wafer support table 3 comes into contact with
only the peripheral portion or part of the lower surface of the
first wafer 1, unevenness on the first wafer 1 supported on the
wafer support table 3 due to particles which may adhere to the
wafer support table 3 or the lower surface of the first wafer 1 can
be prevented.
[0103] The wafer support table 3 preferably has a chuck mechanism
for chucking the first wafer 1. In this embodiment, the wafer
support table 3 has a vacuum chuck mechanism. However, another
chuck mechanism such as an electrostatic chuck mechanism may be
employed.
[0104] The wafer moving mechanism 4 preferably comes into contact
with only the lower surface of the second wafer 2. In this
embodiment, the wafer moving mechanism 4 has a groove 4a for
vacuum-chucking the wafer. To chuck the second wafer 2, the
pressure in the groove 4a is reduced. With the lower surface of the
second wafer 2 chucked by a wafer chuck portion 4c, the wafer
moving mechanism 4 pivots about a shaft 4b through about
180.degree. to make the second wafer 2 oppose almost parallel to
the first wafer 1. The shaft 4b is located near the middle position
between the wafer support table 3 and the wafer chuck portion
4c.
[0105] The wafer processing apparatus 100 also has, as a mechanism
for adjusting the gap between the two wafers 1 and 2 opposing each
other, a displacement detection section 15 for measuring the
thickness of the first wafer 1 mounted on the wafer support table
3, a displacement detection section 12 for measuring the thickness
of the second wafer 2 chucked by the wafer chuck portion 4c, and a
Z-axis stage 5 (FIG. 5) for vertically a moving the wafer support
table 3 on the basis of the measurement results from the
displacement detection sections 12 and 15 to adjust the gap between
the wafers 1 and 2 to a set value.
[0106] The wafer processing apparatus 100 also has a press
mechanism 6 for pressing the upper wafer 2 near its central portion
while the two wafers 1 and 2 are supported to be opposite to each
other. A press pin 6a of the press mechanism 6 pivots about a shaft
6b to be close to the lower surface of the upper wafer 2 after the
two wafers 1 and 2 are supported to be opposite to each other. When
the wafer chuck portion 4c of the wafer moving mechanism 4 cancels
chucking of the upper wafer 2, the press mechanism 6 presses the
upper wafer 2 by pressing the press pin 6a against the lower
surface of the wafer 2. The two wafers 1 and 2 gradually come into
contact with each other outward from the pressed portion, and
accordingly, the gas between the wafers land 2 is expelled outward.
Consequently, no gas remains entrapped between the wafers 1 and
2.
[0107] The wafer 2 is preferably pressed by the press pin 6a almost
simultaneously with cancel of chucking of the wafer 2 by the wafer
chuck portion 4c. In this case, pressing can be started while
maintaining the gap between the two wafers 1 and 2, which is
adjusted to the set value. This uniforms the quality of the wafer
obtained by bringing the two wafers into contact. In addition, gas
entrapment between the wafers 1 and 2 can be more effectively
prevented. Furthermore, shift of the wafers 1 and 2 can be
prevented.
[0108] The press mechanism 6 incorporates a vibrator (e.g., a
piezoelectric element) for vibrating the press pin-6a. By vibrating
the press pin 6a which is pressing the wafer 2, the gas between the
wafers 1 and 2 can be efficiently removed.
[0109] Pressing the wafer 2 by the press pin 6a may be controlled
at another timing. For example, pressing may be performed at a
predetermined timing before a predetermined amount of gas between
the wafers 1 and 2 is removed after chucking of the wafer 2 is
canceled, at a timing upon counting a predetermined time after
chuck of the wafer 2 is canceled, or at a predetermined timing
after chucking of the wafer 2 is canceled and before the distance
between the wafers 1 and 2 becomes a predetermined distance or less
due to the weight of the wafer 2.
[0110] The wafer processing apparatus 100 also has a wafer transfer
robot 10 for setting the wafers 1 and 2 on the wafer support table
3 and the wafer chuck portion 4c, respectively, and receiving the
wafers in contact with each other from the wafer support table 3,
and a wafer alignment section 11.
[0111] In this wafer processing apparatus 100, before the start of
wafer contact processing, wafer cassettes 7 and 8 storing wafers 1
and 2 which have not been processed yet, and a wafer cassette 9 for
storing processed wafers are set at predetermined positions. In
this embodiment, wafers 1 and 2 which have not been processed yet
are stored in the wafer cassettes 7 and 8, respectively, while
having the lower surfaces facing down.
[0112] When the start of wafer contact processing is instructed
with an operation switch 16b on a control panel 16, the wafer
transfer robot 10 chucks the lower surface of an unprocessed wafer
1 stored in the wafer cassette 7, and transfers the wafer 1 to the
wafer alignment section 11. The wafer alignment section 11 detects
the central position and direction (e.g., the orientation flat and
notch position) of the transferred wafer 1 using a sensor and
adjusts the central position and direction. The wafer alignment
section 11 preferably comes into contact with only the lower
surface of the wafer 1.
[0113] After this, the wafer transfer robot 10 receives the aligned
wafer 1 and sets it at a predetermined position on load pins 13
which project from the wafer support table 3 through load pin holes
3e. After the wafer 1 is mounted on the load pins 13, the wafer
support table 3 moves upward, so the wafer 1 is supported by the
wafer support table 3. Since the wafer 1 has already been aligned
by the wafer alignment section 11 and transferred to the wafer
support table 3 while maintaining its positional relationship, the
central position and direction of the wafer 1 need not be adjusted
again on the wafer support table 3. However, alignment of the wafer
1 may be performed on the wafer support table 3.
[0114] Next, the wafer transfer robot 10 extracts an unprocessed
wafer 2 from the wafer cassette 8. With the same procedures as
described above, the wafer alignment section 11 adjusts the central
position and direction of the wafer 2, and then, the wafer 2 is set
at a predetermined position on load pins 14 which project from the
wafer chuck portion 4c of the wafer moving mechanism 4. After the
wafer 2 is mounted on the load pins 14, the wafer chuck portion 4c
pivots about the shaft 4b until the wafer chuck portion 4c contacts
the lower surface of the wafer 2. The pressure in the groove 4a is
reduced, so the wafer 2 is chucked by the wafer chuck portion 4c.
As described above, since the wafer 2 has already been aligned by
the wafer alignment section 11 and chucked by the wafer chuck
portion 4c while maintaining its positional relationship, the
central position and direction of the wafer 2 need not be adjusted
again in chucking. In chucking the wafer 2, the load pins 14 may be
retracted downward instead of pivoting the wafer chuck portion
4c.
[0115] While the wafers 1 and 2 are being supported by the wafer
support table 3 and the wafer chuck portion 4c, respectively, the
displacement detection sections 15 and 12 measure the thicknesses
of the wafers 1 and 2. More specifically, the displacement
detection sections 15 and 12 move sensors 15a and 12a close to the
upper portions of the wafers 1 and 2, irradiate the wafers 1 and 2
with light, and measure the thicknesses of the wafers 1 and 2 on
the basis of the reflected light, respectively.
[0116] When measurement of the thicknesses of the wafers 1 and 2 is
ended, the wafer chuck portion 4c pivots about the shaft 4b through
about 180.degree. to make the wafer 2 oppose almost parallel to the
wafer 1, as described above. After this, the gap between the wafers
1 and 2 is adjusted by the Z-axis stage 5, and the wafer 2 is
pressed by the press pin 6a, thus completing contact
processing.
[0117] When contact processing is ended, the wafer support table 3
is moved downward by the Z-axis stage 5, and the processed wafers
are supported by the load pins 13. After this, the wafer transfer
robot 10 receives the processed wafers and stores them in the wafer
cassette 9.
[0118] By repeatedly executing the above procedure, a plurality of
wafers stored in the wafer cassettes 7 and 8 can be continuously
processed.
[0119] The arrangement of the wafer support table 3 will be
described next. The wafer support table 3 has a circular central
portion 3c and an annular peripheral portion 3d. Two chuck grooves
3a and 3b are formed in the chuck surface of the peripheral portion
3d (surface where the wafer 1 is chucked) to vacuum-chuck the wafer
1.
[0120] The chuck grooves 3a and 3b communicate with a suction hole
18a which is coupled to a pipe 18 having a valve 19 midway. A
vacuum pump 20 is connected to one end of the pipe 18. Wafer
chucking by the chuck grooves 3a and 3b can be controlled by
opening or closing the valve 19.
[0121] When the wafer 2 is to be pressed by the press pin 6a, the
valve 19 is opened to lower the pressure in the chuck grooves 3a
and 3b, thereby chucking the wafer 1. When the wafer 1 is chucked
by the chuck grooves 3a and 3b formed in the surface of the
peripheral portion 3d with a flat surface, the first wafer 1 is
corrected to be nearly flat.
[0122] In this state, the wafer 2 is pressed at its central
portion, as shown in FIG. 4. First, the central portions of the two
wafers 1 and 2 come into contact, and then, the contact portion
gradually expands outward. At this time, the contact portion
expands in all directions almost at a constant speed.
[0123] The operation of the wafer processing apparatus 100 in
bringing two wafers into contact will be described next with
reference to FIGS. 5 to 9.
[0124] When the wafers 1 and 2 are mounted on the load pins 13 and
14 by the wafer transfer robot 10, respectively, the Z-axis stage 5
moves the wafer support table 3 upward to a predetermined position
at which the wafer 1 is supported, and the wafer moving mechanism 4
pivots the wafer chuck portion 4c about the shaft 4b to a
predetermined position at which the wafer 2 can be chucked, as
shown in FIG. 5.
[0125] Next, as shown in FIG. 6, the sensors 15a and 12a of the
displacement detection sections 15 and 12 move onto the wafers 1
and 2 to measure the thicknesses of the wafers 1 and 2,
respectively. After the thicknesses of the wafers 1 and 2 are
measured, the sensors 15a and 12a return to the initial positions
shown in FIG. 5.
[0126] As shown in FIG. 7, the wafer moving mechanism 4 pivots the
wafer chuck portion 4c about the shaft 4b through around
180.degree. to make the wafers 1 and 2 opposite to each other
almost in the horizontal direction. The height of the wafer support
table 3 is adjusted by the Z-axis stage 5 on the basis of the
measured thicknesses of the wafers 1 and 2 to set the gap between
the wafers 1 and 2 at a set value. The gap is preferably 20 to 100
.mu.m at the central portion of the wafers and, more preferably, 30
to 60 .mu.m. The wafer processing apparatus 100 opens the valve 19
so that the peripheral portion of the lower surface of the wafer 1
is chucked by the chuck surface of the peripheral portion 3d of the
wafer support table 3. With this operation, the wafer 1 is
corrected to be almost flat.
[0127] As shown in FIG. 8, the press pin 6a is pivoted about the
shaft 6b to be close to the lower surface of the wafer 2 (e.g., a
position at which the press pin 6a is substantially in contact with
the lower surface of the wafer 2).
[0128] Subsequently, as shown in FIG. 9, the lower surface of the
wafer 2 is pressed by the press pin 6a when chucking of the wafer 2
by the wafer chuck portion 4c is canceled. The wafers 1 and 2
gradually come into contact with each other outward from the
central portion, and finally, the entire surfaces are in contact
with each other.
[0129] After the press mechanism 6 is returned to the initial state
(state shown in FIG. 5), the wafer chuck portion 4c is returned to
the initial state (state shown in FIG. 5). The valve 19 is closed
to set the interior of the chuck groove 3a to the atmospheric
pressure (chucking of the wafer 1 is canceled), and then, the wafer
support table 3 is moved downward, so that the wafers in contact
with each other are supported by the load pins 13. In this state,
the wafer transfer robot 10 chucks the lower surface of the wafers
in contact with each other, transfers them to the wafer cassette 9,
and stores them in the wafer cassette 9.
[0130] FIG. 10 is a block diagram showing the arrangement of the
control system of the wafer processing apparatus 100. A control
section 17 controls the wafer transfer robot 10, the wafer
alignment section 11, the displacement detection sections 12 and
15, the Z-axis stage 5, the wafer moving mechanism 4, the press
mechanism 6, the panel section 16, and a valve control section 19a
by a CPU 17a which operates on the basis of a program 17b.
[0131] FIG. 11 is a flow chart showing the control procedure based
on the program 17b. The operation of the control system of the
wafer processing apparatus 100 will be described with reference to
the flow chart.
[0132] When the start of contact processing is instructed by
operating the operation switch 16b, constituent elements connected
to the control section 17 are initialized in step S101. In this
initialization step, the presence and positions of the wafer
cassettes 7, 8, and 9 are also confirmed. If preparation is not
complete, this is indicated on a display panel 16a to warn the
operator.
[0133] In step S102, a wafer 1 stored in the wafer cassette 7 is
chucked by controlling the wafer transfer robot 10. In step S103,
the chucked wafer 1 is transferred to the wafer alignment section
11 and aligned (central position and direction). In step S104, the
wafer 1 is set at a predetermined position on the load pins 13
projecting from the wafer support table 3 by controlling the wafer
transfer robot 10. The wafer support table 3 is moved upward to a
predetermined position by controlling the Z-axis stage 5.
[0134] In step S105, a wafer 2 stored in the wafer cassette 8 is
chucked by controlling the wafer transfer robot 10. In step S106,
the wafer 2 is transferred to the wafer alignment section 11 and
aligned (central position and direction). In step S107, the wafer 2
is set at a predetermined position on the load pins 14 projecting
from the wafer chuck portion 4c by controlling the wafer transfer
robot 10. The wafer chuck portion 4c is pivoted about the shaft 4b
through a predetermined angle by controlling a pivoting motor 4d of
the wafer moving mechanism 4, so the wafer 2 is chucked by the
wafer chuck portion 4c.
[0135] In step S108, the sensor 15a is moved to a predetermined
position on the wafer 1 by controlling a driving section 15b of the
displacement detection section 15, so the thickness of the wafer 1
is measured by the sensor 15a.
[0136] In step S109, the sensor 12a is moved to a predetermined
position on the wafer 2 by controlling a driving section 12b of the
displacement detection section 12, so the thickness of the wafer 2
is measured by the sensor 12a.
[0137] In step S110, the wafer chuck portion 4c is pivoted about
the shaft 4b through about 180.degree. by controlling the pivoting
motor 4d of the wafer moving mechanism 4 to make the wafers 1 and 2
opposite to each other almost in the horizontal direction.
[0138] In step S111, data for adjusting the gap between the wafers
1 and 2 to a set value is prepared on the basis of the measurement
result of the thicknesses of the wafers 1 and 2. The Z-axis stage 5
is controlled on the basis of the data to adjust the gap between
the wafers 1 and 2.
[0139] In step S112, the valve control section 19a opens the valve
19, so the first wafer 1 is chucked by the wafer support table
3.
[0140] In step S113, the press pin 6a is pivoted about the shaft 6b
by controlling a pivoting motor 6d of the press mechanism 6 until
the distal end portion of the press pin 6a roughly contacts the
lower surface of the wafer 2.
[0141] In step S114, chucking of the wafer 2 by the wafer chuck
portion 4c is canceled. In step S115, the pivoting motor 6d and a
vibrator 6c of the press mechanism 6 are controlled to press the
press pin 6a against the lower surface of the wafer 2 and
simultaneously vibrate the press pin 6a. When step S115 is executed
immediately after step S114, cancel of chucking of the wafer 2 and
pressing can be performed almost simultaneously. Pressing may be
started after step S114, e.g., after a predetermined time is
counted.
[0142] When the wafers 1 and 2 are completely in contact with each
other, the pivoting motor 6d of the press mechanism 6 is controlled
to return the press pin 6a to the initial position in step S116. In
step S117, the pivoting motor 4d of the wafer moving mechanism 4 is
controlled to return the wafer chuck portion 4c to the initial
position.
[0143] In step S118, the valve 19 is closed to return the interior
of the chuck grooves 3a and 3b to the atmospheric pressure, thereby
canceling chucking of the wafer 1. In step S119, the Z-axis stage 5
is controlled to move the wafer support table 3 downward to the
initial state. With this operation, the wafers in contact with each
other are supported by the load pins 13.
[0144] In step S120, the wafer transfer robot 10 is controlled to
transfer the wafers in contact with each other to the wafer
cassette 9 and store them in the wafer cassette 9.
[0145] In step S121, it is determined whether contact processing
has been performed for all wafers stored in the wafer cassettes 7
and 8. If wafers which have not been processed yet remain, the flow
returns to step S102 to repeat the processing. If it is determined
that contact processing has been performed for all wafers, the
series of processing operations are ended. At this time, the
operator is preferably notified of the end of processing by an
indication on the display panel 16a or a buzzer sound.
[0146] As described above, according to the wafer processing
apparatus 100, 1) since pressing is started in synchronism with
cancel of chucking of the upper wafer 2, the gas between the wafers
1 and 2 can be properly removed outward, 2) since the upper wafer 2
does not slide when the wafers 1 and 2 oppose each other, the two
wafers 1 and 2 can be properly positioned, 3) since the gap between
the wafers 1 and 2 can be adjusted to an appropriate distance, the
quality of the manufactured wafer can be uniformed, and the wafers
1 and 2 need not be classified in advance, 4) the surfaces of the
wafers 1 and 2 can be prevented from being contaminated by
particles, 5) damage to the peripheral portions of the wafers can
be prevented, and 6) gas entrapment between the wafers can be
decreased by vibrating the wafers during pressing.
[0147] In addition, according to the wafer processing apparatus
100, only the peripheral portion 3d of the wafer support table 3
comes into contact with the lower surface of the first wafer 1. For
this reason, even when particles adhere to the central portion 3c
of the wafer support table 3 or the central portion of the lower
surface of the first wafer 1, the first wafer can be supported in
an almost flat state. In other words, unevenness on the supported
wafer 1 due to particles which may adhere to the central portion of
the wafer support table or the first wafer can be prevented.
Therefore, when the two wafers are brought into contact with each
other, gas entrapment between the wafers can be effectively
prevented.
Second Embodiment
[0148] In the second embodiment, the structure of the wafer support
table 3 of the wafer processing apparatus 100 according to the
first embodiment is modified. The arrangement of members other than
the wafer support table is the same as in the first embodiment.
FIG. 12 is a sectional view showing the structure of a wafer
support table 31 according to the second embodiment. The wafer
support table 31 is particularly suitable to bring large-diameter
wafers into contact with each other.
[0149] The wafer support table 3' of the second embodiment has,
near its central portion, a deflection prevention portion 3f for
preventing a wafer 1 from deflecting due to its weight or pressing
by a press pin 6a. That table portion where the deflection
prevention portion 3f comes in contact with the first wafer 1 and
that table portion where a peripheral portion 3b comes in contact
with the first wafer 1 are preferably substantially positioned in
the same plane. In the example shown in FIG. 12, the portion where
the deflection prevention portion 3f comes in contact with the
wafer has an annular shape. Another shape (e.g., a matrix or
needlepoint array) may be employed. The wafer support table 3' can
be manufactured by, e.g., lapping. The deflection prevention
portion 3f is preferably located near the center of the wafer
support table 3'. However, even when the deflection prevention
portion 3f is located at an arbitrary position in a central portion
3c, the same effect as described above can be obtained.
[0150] As described above, when the deflection prevention portion
3f is used, the first wafer 1 can be prevented from deflecting, and
the influence of particles can be reduced, as in the first
embodiment.
Application Example of Wafer Processing Apparatus
[0151] An application example of the wafer processing apparatus
according to the first or second embodiment will be described
below. FIGS. 13A to 13F are views showing steps in manufacturing a
wafer having, e.g., an SOI structure.
[0152] A single-crystalline Si wafer 501 for forming the first
wafer 1 is prepared. A porous Si layer 502 is formed on a major
surface of the single-crystalline Si wafer 501 (FIG. 13A). At least
one non-porous layer 503 is formed on the porous Si layer 502 (FIG.
13B). As the non-porous layer 503, a single-crystalline Si layer, a
polycrystalline Si layer, an amorphous Si layer, a metal layer, a
semiconductor compound layer, or a superconductor layer is
suitable. A device such as a MOSFET may be formed on the non-porous
layer 503.
[0153] An SiO.sub.2 layer 504 is formed on the non-porous layer 503
to obtain a first wafer 1 (FIG. 13C). The first wafer 1 with the
SiO.sub.2 layer 504 facing up is stored in a wafer cassette 7.
[0154] A second wafer 2 is prepared. The second wafer 2 with its
surface facing up is stored in a wafer cassette 8.
[0155] The wafer shown in FIG. 13C may be stored in the wafer
cassette 8 as the second wafer while another wafer may be stored in
the wafer cassette 7 as the first wafer. In this case, the wafer
shown in FIG. 13C is transferred to the wafer support table 3, and
another wafer is transferred to a wafer moving mechanism 4.
[0156] In this state, the wafer processing apparatus is operated.
The first wafer 1 and the second wafer 2 come into contact with
each other while sandwiching the SiO.sub.2 layer 504 (FIG. 13D),
and stored in a wafer cassette 9.
[0157] The wafers in contact with each other (FIG. 13D) may be
subjected to anode bonding, pressing, or heat treatment, as needed,
or these processing operations may be combined to firmly bond the
wafers.
[0158] As the second wafer 2, an Si wafer, an Si wafer with an
SiO.sub.2 layer formed thereon, a transparent wafer consisting of
silica glass, or a sapphire wafer is suitably used. However, any
other wafer can be used as the second wafer 2 as far as it has a
sufficiently flat surface to be bonded.
[0159] Next, the first wafer 1 is removed from the second wafer 2
to expose the porous Si layer 502 (FIG. 13E). The porous Si layer
502 is selectively etched and removed. FIG. 13F schematically shows
the wafer obtained by the above manufacturing method.
[0160] According to this manufacturing method, the two wafers are
brought into contact with each other while appropriately removing
any gas between the wafers, so a high-quality wafer can be
manufactured.
[0161] According to the present invention, substrates can be
brought into contact with each other at high quality without
leaving any gas entrapped.
Third Embodiment
[0162] FIG. 16 is a plan view showing the arrangement of a wafer
(substrate) support table 31 according to the third embodiment of
the present invention.
[0163] The wafer support table 31 can be manufactured by
fabricating a generally commercially available silicon wafer, e.g.,
a silicon wafer for manufacturing a semiconductor device complying
with the SEMI standard or JAIDA standard. A wafer used to
manufacture a semiconductor device has high surface planarity. For
this reason, when the surface is used as a chuck surface for
chucking a wafer to be supported, a high-precision wafer support
table can be easily manufactured. Hence, a wafer support table
excellent in mass productivity and cost can be obtained.
[0164] For example, the general lithography technique can be
employed to fabricate the silicon wafer. Since a pattern can be
formed at an accuracy of, e.g., submicron order, lithography is
applicable to manufacture the wafer support table according to the
third embodiment.
[0165] The wafer support table 31 has two bank-shaped sealing
portions 31a and 31b and a suction port 31d. The gas in the space
defined by the two sealing portions 31a and 31b and the wafer to be
chucked and supported is exhausted through the suction port 31d,
thereby chucking the wafer.
[0166] On the wafer support table 31, a number of pin-shaped
deflection prevention portions 31c is formed between the sealing
portions 31a and 31b to prevent the chucked wafer from deflecting
upon reducing the pressure between the two sealing portions 31a and
31b. In this embodiment, the deflection prevention portions 31c are
formed only between the sealing portions 31a and 31b. However, the
deflection prevention portions 31c may be formed at the central
portion.
[0167] As the surfaces of the sealing portions 31a and 31b and the
deflection prevention portions 31c which come in contact with the
object to be chucked, the surface of the silicon wafer as the
material of the wafer support table 31 is directly used.
[0168] The wafer support table 31 has pin holes 31e in which load
pins (to be described later) used to load/unload the wafer to be
chucked are inserted.
[0169] FIG. 17 is a sectional view showing part of the wafer
support table 31 shown in FIG. 16. A height h of the sealing
portions 31a and 31b and the deflection prevention portions 31c is
preferably about 50 .mu.m. Widths d4 and d1 of the sealing portions
31a and 31b are preferably made small to some extent to prevent
particles from being sandwiched by the sealing portions 31a and 31b
and the wafer to be chucked, and the widths are preferably, e.g.,
approximately 0.2 mm. From the same viewpoint, the diameter of the
deflection prevention portions 31c is preferably made small to some
extent, and the diameter is preferably, e.g., about 0.2 mm.
[0170] FIG. 18 is a sectional view showing the arrangement of a
wafer support apparatus 3 including the wafer support table 31
shown in FIG. 16. This wafer support apparatus 3 is constructed by
vacuum-chucking the wafer support table 31 on a base 32.
[0171] The base 32 has an annular groove 32a for vacuum-chucking
the wafer support table 31, and a suction hole 32b for exhausting
the gas in the groove 32a. The wafer support table 31 is chucked by
reducing the pressure in the groove 32a. The suction hole 32b is
connected to a vacuum pump 20 through a pipe 118a having a valve
119a midway.
[0172] The base 32 also has a suction hole 32c for coupling the
suction port 31d communicating with the lower surface of the wafer
support table 31 to the vacuum pump 20 through a pipe 118b having a
valve 119b midway.
[0173] When the wafer support table 31 is to be mounted on the base
32, the valve 119a is opened. When the wafer 1 to be processed is
to be mounted on the wafer support table 31, the valve 119b is
opened.
[0174] The base 32 also has pin holes 32d in which the load pins
used to load/unload the wafer 1 on/from the wafer support table 31
are inserted.
[0175] The wafer support table 31 is preferably regularly cleaned
to remove particles which may adhere to the chuck surface of the
wafer 1. As described above, when the wafer support table 31 is
manufactured by fabricating the silicon wafer used to manufacture a
semiconductor device, a commercially available wafer carrier can be
used for cleaning. In this case, the wafer support table 31 can be
accommodated in the commercially available wafer carrier and
cleaned using a general wafer cleaning apparatus.
[0176] Steps in manufacturing the wafer support table 31 will be
described below. FIGS. 19A to 19N are views showing steps in
manufacturing the wafer support table 31 by applying the general
lithography technique.
[0177] An Si wafer 201a for manufacturing a semiconductor device is
prepared. As shown in FIG. 19A, a film 202a for forming a mask
pattern which is to be used in etching the Si wafer 201a later is
formed on the upper, lower, and side surfaces of the Si wafer 201a.
As the material of the film 202a, SiO.sub.2 by thermal oxidation or
Si.sub.3N.sub.4 by CVD is preferably used.
[0178] Next, as shown in FIG. 19B, a photoresist film 203a is
formed on the wafer shown in FIG. 19A.
[0179] The photoresist film 203a is irradiated with UV light
through a photomask (first mask) for forming the sealing portions
31a and 31b and the deflection prevention portions 31c, thereby
printing a mask pattern. By developing the mask pattern, a
patterned photoresist film 203b is formed, as shown in FIG. 19C.
Since the fabrication accuracy in the planar direction can be lower
than that required for a general semiconductor device, an exposure
apparatus with low accuracy can be used to print the mask
pattern.
[0180] As shown in FIG. 19D, the film 202a is dry-etched using the
photoresist film 203b as a mask, thereby exposing the Si wafer
201a. With this process, a patterned film 202b is formed on the Si
wafer 201a. Next, as shown in FIG. 9E, the patterned photoresist
film 203b is removed.
[0181] As shown in FIG. 19F, the wafer shown in FIG. 19E is etched.
As this etching, wet etching using an alkali solution as an etchant
is preferable. As the alkali solution, a solution of ammonia, or an
organic ammonia-based solution can be used. For example, to form
sealing portions 31a and 31b and a deflection prevention portions
31c having a height h of 50 .mu.m, as shown in FIG. 18, the wafer
201a is etched to a depth of 50 .mu.m.
[0182] As shown in FIG. 19G, the patterned film 202b is removed
using hydrofluoric acid. With this process, an Si wafer 201b having
sealing portions 31a and 31b and the deflection prevention portions
31c is formed.
[0183] Subsequently, as shown in FIG. 19H, a film 204a for forming
a mask pattern which is to be used in etching the Si wafer 201b
later is formed on the upper, lower, and side surfaces of the Si
wafer 201b having the sealing portions 31a and 31b and the
deflection prevention portions 31c. As the material of the film
204a, SiO.sub.2 by thermal oxidation or Si.sub.3N.sub.4 by CVD is
preferably used.
[0184] A photoresist film 205a is formed on the lower surface of
the wafer shown in FIG. 19I (surface on the opposite side of the
surface having the sealing portions 31a and 31b and the deflection
prevention portions 31c).
[0185] The photoresist film 205a is irradiated with UV light
through a photomask (second mask) for forming a suction port 31d
and pin holes 31e, thereby printing the mask pattern. By developing
the mask pattern, a photoresist film 205b having a hole 211 for
forming a suction port 31d and holes 212 for forming pin holes 31e
are formed, as shown in FIG. 19J.
[0186] As shown in FIG. 19K, the film 204a is dry-etched using the
photoresist film 205b as a mask, thereby exposing the Si wafer
201b. With this process, a patterned photoresist film 204b is
formed on the Si wafer 201b. As shown in FIG. 19L, the patterned
photoresist film 204b is removed.
[0187] As shown in FIG. 19M, the wafer shown in FIG. 19L is etched
until a suction port 31d and pin holes 31e are formed. As this
etching, wet etching using an alkali solution as an etchant is
preferable. As the alkali solution, a solution of ammonia, or an
organic ammonia-based solution can be used.
[0188] Finally, as shown in FIG. 19N, the patterned photoresist
film 204b is removed using hydrofluoric acid, thus completing the
wafer support table 31.
[0189] In the resultant wafer support table 31, the surface of the
wafer 201a as the material directly serves as the sealing portions
31a and 31b and the deflection prevention portions 31c.
Consequently, when the wafer support table 31 is manufactured using
the wafer 201a having sufficient surface planarity, the surface
need not be processed after the photoresist film 203a is
removed.
[0190] As described above, the wafer support table 31 according to
this embodiment can be easily manufactured at low cost. For
example, when particles adhere to the wafer support table 31, and
the particles can hardly be removed by cleaning, the wafer support
table can be exchanged with another wafer support table 31 at low
cost.
[0191] The above wafer support apparatus 3 is suitably used to
support one of two wafers to be overlaid and brought into contact
with each other. An apparatus and method of bringing first and
second wafers into contact with each other by pressing the lower
surface of the second wafer while the first wafer is supported by
the wafer support apparatus 3 to oppose the second wafer will be
described below. These apparatus and method are suitably used to
practice the method of bonding two wafers to manufacture a wafer
having, e.g., an SOI structure.
[0192] FIG. 20 is a view showing a state wherein two wafers are
brought into contact with each other using the wafer support
apparatus 3. To bring the two wafers into contact with each other,
the first wafer 1 is chucked on the wafer support table 31, and
then, the second wafer 2 is set to oppose the first wafer 1. In
this state, the lower surface of the second wafer 2 is pressed near
its central portion by a press pin 6a. First, the wafers 1 and 2
come into contact at the central portion first. The contact portion
gradually expands outward, and finally, the entire surfaces of the
wafers 1 and 2 are completely in contact with each other. According
to this method, the two wafers can be brought into contact with
each other without leaving any gas between the two wafers 1 and
2.
[0193] When the wafer support table 3 is to be applied to bring two
wafers into contact with each other, the chuck portion of the wafer
support table 3, which is made up of the sealing portions 31a and
31b, is preferably brought into contact only with the peripheral
portion (and more preferably, the outermost portion) of the first
wafer 1. The chuck portion is preferably annular. As described
above, the wafer support table 3 preferably has the deflection
prevention portions 31c. The deflection prevention portions 31c are
preferably formed between the sealing portions 31a and 31b. When
the wafer support table 3 comes into contact only with the lower
surface of the first wafer, the surface of the first wafer 1 can be
prevented from being contaminated by particles. In addition, damage
to the edge portion of the first wafer 1 can be prevented.
Furthermore, when the wafer support table 3 comes into contact only
with the peripheral portion as part of the lower surface of the
first wafer, unevenness on the first wafer 1 supported on the wafer
support table 3 due to particles which may adhere to the wafer
support table 3 or the lower surface of the first wafer 1 can be
prevented.
[0194] A wafer processing apparatus incorporating the wafer support
apparatus 3 will be described next.
[0195] FIG. 21 is a perspective view schematically showing the
overall arrangement of the wafer processing apparatus according to
the third embodiment. FIG. 22 is an enlarged view of part of FIG.
21. FIGS. 23 to 27 are sectional views of a wafer processing
apparatus 1000 shown in FIGS. 21 and 22 taken along a line A-A'.
FIGS. 23 to 27 show the operation of bringing two wafers into
contact.
[0196] This wafer processing apparatus 1000 continuously overlays
and contacts two wafers, and is conveniently used to practice the
method of bonding two wafers to manufacture a wafer having, e.g.,
and SOI structure.
[0197] The wafer processing apparatus 1000 has the wafer support
apparatus 3 for supporting the first wafer 1 (FIG. 20) from its
lower surface, and a wafer moving mechanism 4 for chucking the
second wafer 2 (FIG. 20) from its lower surface and making the
second wafer 2 oppose almost parallel to the first wafer 1.
[0198] As described above, the wafer support apparatus 3 is built
by mounting the wafer support table 31 on the base 32 and opening
the valve 119a to chuck the wafer support table 31 on the base
32.
[0199] The wafer moving mechanism 4 preferably comes into contact
only with the lower surface of the second wafer 2. In this
embodiment, the wafer moving mechanism 4 has a groove 4a for
vacuum-chucking the wafer. To chuck the second wafer 2, the
pressure in the groove 4a is reduced. With the lower surface of the
second wafer 2 chucked by a wafer chuck portion 4c, the wafer
moving mechanism 4 pivots about a shaft 4b through about
180.degree. to make the second wafer 2 oppose almost parallel to
the first wafer 1. The shaft 4b is located near the middle position
between the wafer support apparatus 3 and the wafer chuck portion
4c.
[0200] The wafer processing apparatus 1000 also has, as a mechanism
for adjusting the gap between the two wafers 1 and 2 facing each
other, a displacement detection section 15 for measuring the
thickness of the first wafer 1 mounted on the wafer support
apparatus 3, a displacement detection section 12 for measuring the
thickness of the second wafer 2 chucked by the wafer chuck portion
4c, and a Z-axis stage 5 (FIG. 23) for vertically moving the wafer
support apparatus 3 on the basis of the measurement results from
the displacement detection sections 12 and 15 to adjust the gap
between the wafers 1 and 2 to a set value.
[0201] The wafer processing apparatus 1000 also has a press
mechanism 6 for pressing the upper wafer 2 near its central portion
while the two wafers 1 and 2 are supported to be opposite to each
other. A press pin 6a of the press mechanism 6 pivots about a shaft
6b to be close to the lower surface of the upper wafer 2 after the
two wafers 1 and 2 are supported to be opposite to each other. When
the wafer chuck portion 4c of the wafer moving mechanism 4 cancels
chucking of the upper wafer 2, the press mechanism 6 presses the
upper wafer 2 by pressing the press pin 6a against the lower
surface of the wafer 2. The two wafers 1 and 2 gradually come into
contact with each other outward from the pressed portion, and
accordingly, the gas between the wafers land 2 is expelled outward.
As a consequence, no gas remains entrapped between the wafers 1 and
2.
[0202] The wafer 2 is preferably pressed by the press pin 6a almost
simultaneously with cancel of chucking of the wafer 2 by the wafer
chuck portion 4c. In this case, pressing can be started while
maintaining the gap between the two wafers 1 and 2, which is
adjusted to the set value. This uniforms the quality of the wafer
obtained by bringing the two wafers into contact. In addition, gas
entrapment between the wafers 1 and 2 can be more effectively
prevented. Furthermore, shift of the wafers 1 and 2 can be
prevented.
[0203] The press mechanism 6 incorporates a vibrator (e.g., a
piezoelectric element) for vibrating the press pin 6a. By vibrating
the press pin 6a which is pressing the wafer 2, the gas between the
wafers land 2 can be efficiently removed.
[0204] Pressing the wafer 2 by the press pin 6a may be controlled
at another timing. For example, pressing may be performed at a
predetermined timing before a predetermined amount of gas between
the wafers 1 and 2 is removed after chucking of the wafer 2 is
canceled, at a timing upon counting a predetermined time after
chuck of the wafer 2 is canceled, or at a predetermined timing
after chucking of the wafer 2 is canceled and before the distance
between the wafers 1 and 2 becomes a predetermined distance or less
due to the weight of the wafer 2.
[0205] The wafer processing apparatus 1000 also has a wafer
transfer robot 10 for setting the wafers 1 and 2 on the wafer
support apparatus 3 and the wafer chuck portion 4c, respectively,
and receiving the wafers in contact with each other from the wafer
support apparatus 3, and a wafer alignment section 11.
[0206] In this wafer processing apparatus 1000, before the start of
wafer contact processing, wafer cassettes 7 and 8 storing
unprocessed wafers 1 and 2, and a wafer cassette 9 for storing
processed wafers are set at predetermined positions. In this
embodiment, unprocessed wafers 1 and 2 are stored in the wafer
cassettes 7 and 8, respectively, while facing the lower surfaces
down.
[0207] When the start of wafer contact processing is instructed
with an operation switch 16b on a control panel 16, the wafer
transfer robot 10 chucks the lower surface of an unprocessed wafer
1 stored in the wafer cassette 7, and transfers the wafer 1 to the
wafer alignment section 11. The wafer alignment section 11 detects
the central position and direction (e.g., the orientation flat or
notch position) of the transferred wafer 1 using a sensor and
adjusts the central position and direction. The wafer alignment
section 11 preferably comes contact with only the lower surface of
the wafer 1.
[0208] After this, the wafer transfer robot 10 receives the aligned
wafer 1 and sets it at a predetermined position on load pins 13
which project from the wafer support apparatus 3 through the pin
holes 31e and 32d. After the wafer 1 is mounted on the load pins
13, the wafer support apparatus 3 moves upward, so the wafer 1 is
supported by the wafer support apparatus 3. Since the wafer 1 has
already been aligned by the wafer alignment section 11 and
transferred to the wafer support apparatus 3 while maintaining its
positional relationship, the central position and direction of the
wafer 1 need not be adjusted again on the wafer support apparatus
3. However, alignment of the wafer 1 may be performed on the wafer
support apparatus 3.
[0209] Next, the wafer transfer robot 10 extracts an unprocessed
wafer 2 from the wafer cassette 8. With the same procedures as
described above, the wafer alignment section 11 adjusts the central
position and direction of the wafer 2, and then, the wafer 2 is set
at a predetermined position on load pins 14 which project from the
wafer chuck portion 4c of the wafer moving mechanism 4. After the
wafer 2 is mounted on the load pins 14, the wafer chuck portion 4c
pivots about the shaft 4b until the wafer chuck portion 4c contacts
the lower surface of the wafer 2. The pressure in the groove 4a is
reduced, so the wafer 2 is chucked by the wafer chuck portion 4c.
As described above, since the wafer 2 has already been aligned by
the wafer alignment section 11 and chucked by the wafer chuck
portion 4c while maintaining its positional relationship, the
central position and direction of the wafer 2 need not be adjusted
again in chucking. In chucking the wafer 2, the load pins 14 may be
retracted downward instead of pivoting the wafer chuck portion
4c.
[0210] While the wafers 1 and 2 are being supported by the wafer
support apparatus 3 and the wafer chuck portion 4c, respectively,
the displacement detection sections 15 and 12 measure the
thicknesses of the wafers 1 and 2. More specifically, the
displacement detection sections 15 and 12 move sensors 15a and 12a
close to the upper portions of the wafers 1 and 2, irradiate the
wafers 1 and 2 with light, and measure the thicknesses of the
wafers 1 and 2 on the basis of the reflected light,
respectively.
[0211] When measurement of the thicknesses of the wafers 1 and 2 is
ended, the wafer chuck portion 4c pivots about the shaft 4b through
about 180.degree. to make the wafer 2 oppose and almost parallel to
the wafer 1, as described above. After this, the gap between the
wafers 1 and 2 is adjusted by the Z-axis stage 5, and the wafer 2
is pressed by the press pin 6a, thus completing contact
processing.
[0212] When contact processing is ended, the wafer support
apparatus 3 is moved downward by the Z-axis stage 5, and the
processed wafers are supported by the load pins 13. After this, the
wafer transfer robot 10 receives the processed wafers and stores
them in the wafer cassette 9.
[0213] By repeatedly executing the above procedure, a plurality of
wafers stored in the wafer cassettes 7 and 8 can be continuously
processed.
[0214] The operation of the wafer processing apparatus 1000 in
bringing two wafers into contact will be described next with
reference to FIGS. 23 to 27.
[0215] When the wafers 1 and 2 are mounted on the load pins 13 and
14 by the wafer transfer robot 10, respectively, the Z-axis stage 5
moves the wafer support apparatus 3 upward to a predetermined
position at which the wafer 1 is supported, and the wafer moving
mechanism 4 pivots the wafer chuck portion 4c about the shaft 4b to
a predetermined position at which the wafer 2 can be chucked, as
shown in FIG. 23.
[0216] Next, as shown in FIG. 24, the sensors 15a and 12a of the
displacement detection sections 15 and 12 move onto the wafers 1
and 2 to measure the thicknesses of the wafers 1 and 2,
respectively. After the thicknesses of the wafers 1 and 2 are
measured, the sensors 15a and 12a return to the initial positions
shown in FIG. 23.
[0217] As shown in FIG. 25, the wafer moving mechanism 4 pivots the
wafer chuck portion 4c about the shaft 4b through approximately
180.degree. to make the wafers 1 and 2 opposite to each other
almost in the horizontal direction. The height of the wafer support
apparatus 3 is adjusted by the Z-axis stage 5 on the basis of the
measured thicknesses of the wafers 1 and 2 to set the gap between
the wafers 1 and 2 at a set value. The gap is preferably 20 to 100
.mu.m at the central portion of the wafers and, more preferably, 30
to 60 .mu.m. The wafer processing apparatus 1000 opens the valve
119b so that the peripheral portion of the lower surface of the
wafer 1 is chucked by the chuck surface of the peripheral portion
3d of the wafer support apparatus 3. With this operation, the wafer
1 is corrected to be almost flat.
[0218] As shown in FIG. 26, the press pin 6a is pivoted about the
shaft 6b to be close to the lower surface of the wafer 2 (e.g., a
position at which the press pin 6a is substantially in contact with
the lower surface of the wafer 2).
[0219] Subsequently, as shown in FIG. 27, the lower surface of the
wafer 2 is pressed by the press pin 6a when chucking of the wafer 2
by the wafer chuck portion 4c is canceled. The wafers 1 and 2
gradually come into contact with each other outward from the
central portion, and finally, the entire surfaces are in contact
with each other.
[0220] After the press mechanism 6 is returned to the initial state
(state shown in FIG. 23), the wafer chuck portion 4c is returned to
the initial state (state shown in FIG. 23). The valve 119b is
closed to set the interior of the chuck groove 3a to the
atmospheric pressure (chucking of the wafer 1 is canceled), and
then, the wafer support apparatus 3 is moved downward, so that the
wafers in contact with each other are supported by the load pins
13. In this state, the wafer transfer robot 10 chucks the lower
surface of the wafers in contact with each other, transfers them to
the wafer cassette 9, and stores them in the wafer cassette 9.
[0221] FIG. 28 is a block diagram showing the arrangement of the
control system of the wafer processing apparatus 1000. A control
section 17 controls the wafer transfer robot 10, the wafer
alignment section 11, the displacement detection sections 12 and
15, the Z-axis stage 5, the wafer moving mechanism 4, the press
mechanism 6, the panel section 16, and a valve control section 119
by a CPU 17a which operates on the basis of a program 17b.
[0222] The valve control section 119 has a first valve driving
section 119c for controlling switching of the valve 119a and a
second valve driving section 119d for controlling switching of the
valve 119b. The first and second valve driving sections 119c and
119d are controlled by the control section 17.
Attachment/detachment of the wafer support table 31, i.e.,
switching of the valve 119a is controlled on the basis of the
operation of the operation switch 16b of the panel 16.
[0223] FIG. 29 is a flow chart showing the control procedure based
on the program 17b. The operation of the control system of the
wafer processing apparatus 1000 will be described with reference to
the flow chart.
[0224] When the start of contact processing is instructed by
operating the operation switch 16b, constituent elements connected
to the control section 17 are initialized in step S1101. In this
initialization step, the presence and positions of the wafer
cassettes 7, 8, and 9 are also confirmed. If preparation is not
complete, this is indicated on a display panel 16a to warn the
operator.
[0225] In step S1102, a wafer 1 stored in the wafer cassette 7 is
chucked by controlling the wafer transfer robot 10. In step S1103,
the chucked wafer 1 is transferred to the wafer alignment section
11 and positioned (central position and direction). In step S1104,
the wafer 1 is set at a predetermined position on the load pins 13
projecting from the wafer support apparatus 3 by controlling the
wafer transfer robot 10. The wafer support apparatus 3 is moved
upward to a predetermined position by controlling the Z-axis stage
5.
[0226] In step S1105, a wafer 2 stored in the wafer cassette 8 is
chucked by controlling the wafer transfer robot 10. In step S1106,
the wafer 2 is transferred to the wafer alignment section 11 and
aligned (central position and direction). In step S1107, the wafer
2 is set at a predetermined position on the load pins 14 projecting
from the wafer chuck portion 4c by controlling the wafer transfer
robot 10. The wafer chuck portion 4c is pivoted about the shaft 4b
through a predetermined angle by controlling a pivoting motor 4d of
the wafer moving mechanism 4, so the wafer 2 is chucked by the
wafer chuck portion 4c.
[0227] In step S1108, the sensor 15a is moved to a predetermined
position on the wafer 1 by controlling a driving section 15b of the
displacement detection section 15, so the thickness of the wafer 1
is measured by the sensor 15a.
[0228] In step S1109, the sensor 12a is moved to a predetermined
position on the wafer 2 by controlling a driving section 12b of the
displacement detection section 12, so the thickness of the wafer 2
is measured by the sensor 12a.
[0229] In step S1110, the wafer chuck portion 4c is pivoted about
the shaft 4b through about 180.degree. by controlling the pivoting
motor 4d of the wafer moving mechanism 4 to make the wafers 1 and 2
opposite to each other almost in the horizontal direction.
[0230] In step S1111, data for adjusting the gap between the wafers
1 and 2 to a set value is prepared on the basis of the measurement
result of the thicknesses of the wafers 1 and 2. The Z-axis stage 5
is controlled on the basis of the data to adjust the gap between
the wafers 1 and 2.
[0231] In step S1112, the second valve driving section 119d opens
the valve 119b, so the first wafer 1 is chucked by the wafer
support table 31.
[0232] In step S1113, the press pin 6a is pivoted about the shaft
6b by controlling a pivoting motor 6d of the press mechanism 6
until the distal end portion of the press pin 6a roughly contacts
the lower surface of the wafer 2.
[0233] In step S1114, chucking of the wafer 2 by the wafer chuck
portion 4c is canceled. In step S1115, the pivoting motor 6d and a
vibrator 6c of the press mechanism 6 are controlled to press the
press pin 6a against the lower surface of the wafer 2 and
simultaneously vibrate the press pin 6a. When step S1115 is
executed immediately after step S1114, cancel of chucking of the
wafer 2 and pressing can be performed almost simultaneously.
Pressing may be started after step S1114, e.g., after a
predetermined time is counted.
[0234] When the wafers 1 and 2 are completely in contact with each
other, the pivoting motor 6d of the press mechanism 6 is controlled
to return the press pin 6a to the initial position in step S1116.
In step S1117, the pivoting motor 4d of the wafer moving mechanism
4 is controlled to return the wafer chuck portion 4c to the initial
position.
[0235] In step S1118, the valve 119b is closed to return the
interior of the chuck grooves 3a and 3b to the atmospheric
pressure, thereby canceling chucking of the wafer 1. In step S1119,
the Z-axis stage 5 is controlled to move the wafer support
apparatus 3 downward to the initial state. With this operation, the
wafers in contact with each other are supported by the load pins
13.
[0236] In step S1120, the wafer transfer robot 10 is controlled to
transfer the wafers in contact with each other to the wafer
cassette 9 and store them in the wafer cassette 9.
[0237] In step S1121, it is determined whether contact processing
has been performed for all wafers stored in the wafer cassettes 7
and 8. If wafers which have not been processed yet remain, the flow
returns to step S1102 to repeat the processing. If it is determined
that contact processing has been performed for all wafers, the
series of processing operations are ended. At this time, the
operator is preferably notified of the end of processing by an
indication on the display panel 16a or a buzzer sound.
[0238] As described above, according to the wafer processing
apparatus 1000, 1) since pressing is started in synchronism with
cancel of chucking of the upper wafer 2, the gas between the wafers
1 and 2 can be properly removed outward, 2) since the upper wafer 2
does not slide when the wafers 1 and 2 oppose each other, the two
wafers 1 and 2 can be properly positioned, 3) since the gap between
the wafers 1 and 2 can be adjusted to an appropriate distance, the
quality of the manufactured wafer can be uniformed, and the wafers
1 and 2 need not be classified in advance, 4) the surfaces of the
wafers 1 and 2 can be prevented from being contaminated by
particles, 5) damage to the peripheral portions of the wafers can
be prevented, and 6) gas entrapment between the wafers can be
decreased by vibrating the wafers during pressing.
[0239] In addition, according to the wafer processing apparatus
1000, only the sealing portions 31a and 31b and the deflection
prevention portions 31c of the wafer support table 31 come into
contact with the lower surface of the first wafer 1. For this
reason, even when particles adhere to the central portion of the
wafer support apparatus 3 or the central portion of the lower
surface of the first wafer 1, the first wafer can be supported in
an almost flat state. In other words, unevenness on the supported
wafer 1 due to particles which may adhere to the central portion of
the wafer support table or the first wafer can be prevented.
Therefore, when the two wafers are brought into contact with each
other, gas entrapment between the wafers can be effectively
prevented.
[0240] Furthermore, since the wafer processing apparatus 1000
employs the wafer support table 31 manufactured by fabricating a
wafer, the problem of contamination (e.g., metal contamination) by
the material of the wafer support table is also solved.
Application Example of Wafer Processing Apparatus
[0241] An application example of the wafer processing apparatus
according to the third embodiment will be described below. FIGS.
13A to 13F are views showing steps in manufacturing a wafer having,
e.g., an SOI structure.
[0242] A single-crystalline Si wafer 501 for forming the first
wafer 1 is prepared. A porous Si layer 502 is formed on a major
surface of the single-crystalline Si wafer 501 (FIG. 13A). At least
one non-porous layer 503 is formed on the porous Si layer 502 (FIG.
13B). As the non-porous layer 503, a single-crystalline Si layer, a
polycrystalline Si layer, an amorphous Si layer, a metal layer, a
semiconductor compound layer, or a superconductor layer is
suitable. A device such as a MOSFET may be formed on the non-porous
layer 503.
[0243] An SiO.sub.2 layer 504 is formed on the non-porous layer 503
to obtain a first wafer 1 (FIG. 13C). The first wafer 1 with the
SiO.sub.2 layer 504 facing up is stored in the wafer cassette
7.
[0244] The second wafer 2 is prepared. The second wafer 2 with its
surface facing up is stored in the wafer cassette 8.
[0245] The wafer shown in FIG. 13C may be stored in the wafer
cassette 8 as the second wafer while another wafer may be stored in
the wafer cassette 7 as the first wafer. In this case, the wafer
shown in FIG. 13C is transferred to the wafer support table 31, and
another wafer is transferred to the wafer moving mechanism 4.
[0246] In this state, the wafer processing apparatus of the third
embodiment is operated. The first wafer 1 and the second wafer 2
come into contact with each other while sandwiching the SiO.sub.2
layer 504 (FIG. 13D), and stored in the wafer cassette 9.
[0247] The wafers in contact with each other (FIG. 13D) may be
subjected to anode bonding, pressing, or heat treatment, as needed,
or these processing operations may be combined to firmly bond the
wafers.
[0248] As the second wafer 2, an Si wafer, an Si wafer with an
SiO.sub.2 layer formed thereon, a transparent wafer consisting of
silica glass, or a sapphire wafer is suitably used. However, any
other wafer can be used as the second wafer 2 as far as it has a
sufficiently flat surface to be bonded.
[0249] Next, the first wafer 1 is removed from the second wafer 2
to expose the porous Si layer 502 (FIG. 13E). The porous Si layer
502 is selectively etched and removed. FIG. 13F schematically shows
the wafer obtained by the above manufacturing method.
[0250] According to this manufacturing method, the two wafers are
brought into contact with each other while appropriately removing
any gas between the wafers, so a high-quality wafer can be
manufactured.
[0251] According to the present invention, a substrate support
table which can be manufactured at low cost can be provided.
[0252] The present invention is not limited to the above
embodiments and various changes and modifications can be made
within the spirit and scope of the present invention. Therefore, to
apprise the public of the scope of the present invention, the
following claims are made.
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