U.S. patent application number 11/593009 was filed with the patent office on 2007-03-08 for soi wafer and method for producing the same.
This patent application is currently assigned to Shin-Etsu Handotai Co., Ltd.. Invention is credited to Hiroji Aga, Kiyoshi Mitani.
Application Number | 20070054459 11/593009 |
Document ID | / |
Family ID | 18960740 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070054459 |
Kind Code |
A1 |
Aga; Hiroji ; et
al. |
March 8, 2007 |
SOI wafer and method for producing the same
Abstract
The present invention provides a SOI wafer produced by an ion
implantation delamination method wherein a width of a SOI island
region in a terrace portion generated in an edge portion of the SOI
wafer where a surface of a base wafer is exposed is narrower than 1
mm and a density of pit-shaped defects having a size of 0.19 .mu.m
or more existing in a surface of a SOI layer detected by a LPD
inspection is 1 counts/cm.sup.2 or less, and also provides a method
for producing the SOI wafer. Thereby, there is provided a SOI wafer
produced by an ion implantation delamination method wherein
generation of SOI islands generated in delamination can be
suppressed and a defect density of LPDs existing in a surface of
the SOI wafer can be reduced, and a method for producing the same,
so that device failure can be reduced.
Inventors: |
Aga; Hiroji; (Gunma, JP)
; Mitani; Kiyoshi; (Gunma, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Shin-Etsu Handotai Co.,
Ltd.
4-2, Marunouchi 1-chome
Tokyo
JP
|
Family ID: |
18960740 |
Appl. No.: |
11/593009 |
Filed: |
November 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10473352 |
Sep 30, 2003 |
|
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|
PCT/JP02/03162 |
Mar 29, 2002 |
|
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11593009 |
Nov 6, 2006 |
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Current U.S.
Class: |
438/311 ;
257/E21.568; 257/E27.112 |
Current CPC
Class: |
H01L 21/76254
20130101 |
Class at
Publication: |
438/311 ;
257/E27.112 |
International
Class: |
H01L 21/8222 20060101
H01L021/8222 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2001 |
JP |
2001-108643 |
Claims
1. A SOI wafer produced by an ion implantation delamination method
wherein a density of pit-shaped defects having a size of 0.19 .mu.m
or more existing in a surface of a SOI layer detected by a LPD
inspection is 1 counts/cm.sup.2 or less.
2. A method for producing a SOI wafer by an ion implantation
delamination method wherein a lower limit of an implantation dosage
of hydrogen ions or rare gas ions is determined by a delamination
phenomenon, and an upper limit of an implantation dosage of
hydrogen ions or rare gas ions is determined by a width of a SOI
island region in a terrace portion or a density of pit-shaped
defects detected by a LPD inspection of the SOI wafer.
3. A method for producing a SOI wafer by an ion implantation
delamination method wherein an implantation dosage of hydrogen ions
is 5.times.10.sup.16 ions/cm.sup.2 or more and less than
7.5.times.10.sup.16/cm.sup.2.
Description
[0001] This is a divisional application of Application Ser. No.
10/473,352 filed Sep. 30, 2003. The entire disclosure of the prior
application is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method for producing a
SOI wafer by bonding of an ion-implanted wafer and a wafer and
delamination, so-called ion implantation delamination method (also
called a hydrogen ion delamination method or smart-cut method),
which can suppress generation of SOI islands generated in a terrace
portion and generation of LPD generated in a surface of the SOI
wafer, so that device failure can be reduced.
BACKGROUND ART
[0003] The ion implantation delamination method is a method of
producing a SOI wafer by bonding of a wafer into which hydrogen
ions or rare gas ions and a wafer and delamination. However, there
is a case where a SOI layer is not transferred on an edge portion
of the SOI wafer after delamination, and accordingly a terrace
portion where a surface of a base wafer (support substrate) is
exposed is generated. This is mainly due to that the bonding
strength between the bonded wafers is weak in the edge portion of
the wafers, and therefore, a SOI layer is difficult to be
transferred on a base wafer side. When the SOI terrace portion was
observed by a optical microscope, it was found that SOI islands
which are pieces of isolated island-shaped SOI layer were generated
in the edge portion of the SOI layer. It is expected that such SOI
islands come off from the wafer by etching to eliminate a buried
oxide film (may be called a BOX oxide film) during a cleaning by
use of an aqueous solution containing HF (hydrofluoric acid) in a
device fabrication process, and accordingly, they cause device
failure because they adhere to a device fabrication region of the
wafer again as silicon particles.
[0004] FIGS. 1 show cross sectional views of an edge portion of the
SOI wafer produced by an ion implantation delamination method.
[0005] FIG. 1(a) is a SOI wafer 10, and FIG. 1(b) shows the detail
of its edge portion. FIG. 1(b) schematically shows the state that
the SOI wafer 10 comprises a SOI layer 25, a buried oxide film 26
and a base wafer 27, and a terrace portion 43 where a surface of
the base wafer is exposed and SOI islands 42 which are pieces of
isolated island-shaped SOI layer are generated in the edge
portion.
[0006] On the other hand, as SOI wafers produced by the ion
implantation delamination method have been observed by an optical
surface inspection apparatus, it has been found that defects
detected as LPD exist. The LPD (Light Point Defect) is a generic
term of the defect, which appears as a spot when a surface of the
wafer is observed under a condenser lamp. Although this defect has
not been identified, it is considered that a device yield is
affected because nearly all the defects are shallow pits and become
holes which pass through a SOI layer when a SOI layer is oxidized
to be thin.
DISCLOSURE OF THE INVENTION
[0007] The present invention has been accomplished in view of the
above-mentioned problems, and a main object of the present
invention is to provide a SOI wafer produced by an ion implantation
delamination method wherein generation of SOI islands generated in
delamination are suppressed and the defect density of LPD existing
in a surface of the SOI wafer is reduced, and also provide a method
for producing the same, so that the device failure is reduced.
[0008] In order to solve the above problems, the present invention
provides a SOI wafer produced by an ion implantation delamination
method wherein a width of a SOI island region in a terrace portion
generated in an edge portion of the SOI wafer where a surface of a
base wafer is exposed is narrower than 1 mm.
[0009] As described above, in the present invention, the SOI wafer
of which width of a SOI island region in a terrace portion
generated in an edge portion where a surface of a base wafer is
exposed is narrower than 1 mm can be obtained. And if the width of
a SOI island region is narrower than 1 mm like this, there will be
few cases where SOI islands come off from the wafer by etching to
eliminate a buried oxide film during a HF cleaning in a device
fabrication process, and they cause device failure on the ground
that they reattached as silicon particles to a device fabrication
region. Accordingly, the device yield can be improved.
[0010] Further, the SOI wafer according to the present invention is
the SOI wafer produced by an ion implantation delamination method
wherein a density of pit-shaped defects having a size of 0.19 .mu.m
or more existing in a surface of a SOI layer detected by a LPD
inspection is 1 counts/cm.sup.2 or less.
[0011] As described above, in the present invention, a SOI wafer
having extremely few pit-shaped defects can be obtained. And if a
density of pit-shaped defects having a size of 0.19 .mu.m or more
existing in a surface of a SOI layer detected as a LPD is 1
counts/cm.sup.2 or less, device failure can be reduced, and thus,
device yield can be improved.
[0012] Next, a method for producing a SOI wafer according to the
present invention is the method for producing a SOI wafer by an ion
implantation delamination method wherein a lower limit of an
implantation dosage of hydrogen ions or rare gas ions is determined
by a delamination phenomenon, and an upper limit of an implantation
dosage of hydrogen ions or rare gas ions is determined by a width
of a SOI island region in a terrace portion or a density of
pit-shaped defects detected by a LPD inspection of the SOI
wafer.
[0013] If the implantation dosage of hydrogen ions or rare gas ions
is determined by this manner and the ions are implanted, the SOI
wafer such that generation of SOI islands, which is easily
generated in delamination, are suppressed or a defect density of
LPD existing in a surface of the SOI wafer is reduced can be
produced.
[0014] Specifically, the implantation dosage of hydrogen ions is
5.times.10.sup.16 ions/cm.sup.2 or more and less than
7.5.times.10.sup.16 ions/cm.sup.2.
[0015] According to this method, since a width of a region of SOI
islands which are easily generated in delamination can be reduced
to 1 mm or less, the SOI wafer of which a SOI layer can be
certainly transferred to a base wafer and a defect density of LPD
existing in a surface is extremely reduced can be produced.
Further, by determining the implantation dosage in the above range,
the wafer can be stably delaminated.
[0016] As described above, according to the present invention, a
SOI wafer produced by an ion implantation delamination method
wherein generation of SOI islands generated in delamination is
suppressed and a defect density of LPD existing in a surface of the
SOI wafer is reduced and a method for producing the same can be
provided, and accordingly device failure can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1 include schematic diagrams showing a terrace and SOI
islands generating in an edge portion of a SOI wafer;
[0018] (a) A SOI wafer, and (b) an edge portion of the SOI
wafer.
[0019] FIG. 2 includes optical microscope photographs showing
variations of a SOI island region width and a terrace width
depending on the ion implantation dosages (ions/cm.sup.2);
[0020] (a) 5.5.times.10.sup.16, (b) 6.5.times.10.sup.16, and (c)
7.5.times.10.sup.16.
[0021] FIG. 3 is a diagram showing variations of LPD densities
(counts/cm.sup.2) in wafer surfaces relative to ion implantation
dosages.
[0022] FIG. 4 is a flow chart showing one example of a production
process of a SOI wafer according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0023] Hereinafter, the present invention will now be described in
detail.
[0024] Inventors of the present invention found that, in order to
produce a SOI wafer by an ion implantation delamination method
wherein generation of SOI islands generated in delamination is
suppressed or a defect density of LPD existing in a surface of the
SOI wafer is reduced, it is sufficient to control an implantation
dosage of hydrogen ions or rare gas ions within a predetermined
range, and they carefully examined its conditions and accomplished
the present invention.
[0025] A so-called SOI island, which remains at a certain width in
a terrace portion generated in an edge portion of the SOI wafer
where a surface of a base wafer is exposed, can be observed after
delamination heat treatment. And it is considered that delamination
in an ion implantation delamination method occurs due to a growth
of defects induced by hydrogen or rare gas generated during
delamination heat treatment and a strength of rapid volume
expansion due to vaporization of implanted hydrogen or rare gas.
And it is also considered that in the edge portion of the wafer
having the terrace portion, generation of SOI islands is mainly due
to that a bonding strength between the bonded wafers is weak under
the influence of polishing sags in each edge portion of wafer
surfaces to be bonded, and a SOI layer is difficult to be
transferred to a base wafer side.
[0026] In consideration of such characteristics of a delamination
phenomenon, inventors of the present invention found that if an
implantation dosage of hydrogen ions is reduced less than a
conventional dosage of 8.times.10.sup.16 ions/cm.sup.2, a width of
a SOI island region can be reduced.
[0027] Namely, if the implantation dosage of hydrogen ions is
5.times.10.sup.16 ions/cm.sup.2 or more and less than
7.5.times.10.sup.16/cm.sup.2, the width of a SOI island region can
be 1 mm or less and a density of pit-shaped defects having a size
of 0.19 .mu.m or more existing in a surface of a SOI layer detected
by a LPD inspection can be 1 counts/cm.sup.2 or less.
[0028] The reason why the width of a SOI island region is extended
when the implantation dosage of hydrogen ions is
7.5.times.10.sup.16 ions/cm.sup.2 or more is not clear up to the
present. However, it is considered that, if an implantation dosage
is larger than necessary, delamination occurs as hydrogen induced
defects are insufficiently grown since the strength of expansion
due to vaporization of hydrogen is too strong, and thus, the region
where delamination occurs in the state that there is no connection
in a lateral direction like SOI islands is generated.
[0029] Further, if a dosage of hydrogen is less than
5.times.10.sup.16 ions/cm.sup.2, formation of defects and strength
of expansion due to vaporization of hydrogen is not sufficient
since the implantation dosage of hydrogen is too small. Thus, a SOI
layer is only partially transferred to a base wafer, the whole
surface of the wafer is not delaminated. Therefore, it was found
that the SOI wafer can not be made up. Consequently, it is
necessary to control the dosage of hydrogen to 5.times.10.sup.16
ions/cm.sup.2 or more and less than 7.5.times.10.sup.16
ions/cm.sup.2 in the ion implantation delamination method. And in
order to stably perform delamination, the implantation dosage is
preferably 5.5 .times.10.sup.16 ions/cm.sup.2 or more, more
preferably more than 6.times.10.sup.16 ions/cm.sup.2 to produce a
SOI wafer.
[0030] As described above, as to the implantation dosage of
hydrogen ions, the existence of the optimum range of the dosage was
revealed. And, in consideration of the above mechanism, it can be
supposed that this phenomenon is also applied to the case where not
only hydrogen ions but also rare gas ions are implanted.
[0031] Further, when a surface of the SOI layer was observed by an
optical surface inspection apparatus, it was found that a density
of defects detected as LPD depends on an implantation dosage of
hydrogen ions, and when the implantation dosage is
7.5.times.10.sup.16 ions/cm.sup.2 or more, LPDs are extremely
increased. Although LPDs existed about 2 counts/cm.sup.2 or more
when the conventional implantation dosage of 8.times.10.sup.16
ions/cm.sup.2 was implanted, LPDs can be sharply decreased to 1
counts/cm.sup.2 or less.
[0032] As described above, in the present invention, an lower limit
of the implantation dosage of hydrogen ions or rare gas ions is
determined by a delamination phenomenon, and an upper limit of the
implantation dosage of hydrogen ions or rare gas ions is determined
by a width of a SOI island region in the terrace portion or a
density of pit-shaped defects detected by a LPD inspection of the
SOI wafer.
[0033] Hereinafter, the present invention will be further explained
in detail with reference to the drawings.
[0034] FIG. 4 is a flow chart showing one example of the production
process of a SOI wafer in the ion implantation delamination method
in which a hydrogen ion implanted wafer is bonded to a wafer and
delaminated.
[0035] Hereinafter, the case of bonding two silicon wafers will be
mainly explained.
[0036] The ion implantation delamination method in which a SOI
wafer is produced by bonding of an ion-implanted wafer and a wafer
and delamination has, for example, two methods of A and B of which
are different in the order of processing steps. First, the method A
will be explained.
[0037] In the process 1 of the method A, two mirror-polished
silicon wafers are required to be prepared. That is, wafers 20 and
21, which are satisfied with specifications of a device, are
prepared. In the process 2, at least one wafer, i.e., the wafer 20
is thermally oxidized to form an oxide film 30 having a thickness
of about 0.1-2.0 .mu.m on its surface. In the process 3, hydrogen
ions or rare gas ions are implanted (hydrogen ions are implanted
here) into one side surface of the other wafer 21 to form a
microcavity layer (implanted layer) 40 at an average penetration
depth of the ions in parallel with its surface. And its
implantation temperature is preferably 25-450.degree. C. The
process 4 is the process such that a hydrogen ion implanted surface
of the hydrogen ion implanted wafer 21 is brought into contact with
a surface of the oxide film 30 formed on the wafer 20 to be joined
together. By contact of each surface of two wafers under a clean
atmosphere at room temperature, both wafers are joined without an
adhesive agent or the like.
[0038] Next, the process 5 is a delamination heat treatment process
such that the joined wafer is separated into an upper silicon 28
(delamination wafer) and a lower SOI wafer 10 (a SOI layer 25+a
buried oxide film 26+a base wafer 27) by an implanted layer 40
which is a boundary. When heat treatment is performed at a
temperature of 400-600.degree. C. or more under an inert gas
atmosphere, the joined wafer is separated into the upper silicon
and the lower SOI wafer by growth of hydrogen induced defects
generated during the delamination heat treatment process and
strength of rapid volume expansion due to vaporization of implanted
hydrogen. The delaminated upper silicon 28 is removed.
[0039] Additionally, as one of ion implantation delamination
method, it has been developed recently that implantation ions are
implanted in a state of plasma so that the delamination process is
performed at room temperature. In this case, the above delamination
heat treatment is unnecessary.
[0040] Then, in the process 6, since the bonding strength between
the wafers joined with each other in the process 4 which is the
joining process is too weak to be used, as it is, in a device
process, it is necessary to subject the lower SOI wafer 10 to heat
treatment to have a sufficient bonding strength. This heat
treatment is preferably performed for thirty minutes to two hours
at a temperature of 1050-1200.degree. C. under an inert gas
atmosphere.
[0041] Additionally, it is possible to continuously perform
delamination heat treatment in the process 5 and bonding heat
treatment in the process 6, i.e., to continuously perform
delamination heat treatment in the process 5 and bonding heat
treatment in the process 6 without removing the upper silicon wafer
to be delaminated in the process 5 from the lower SOI wafer, or it
is also possible to perform heat treatment as combining the heat
treatment in processes 5 with the heat treatment in processes
6.
[0042] Then, in the process 7, which is a touch polishing process,
mirror-polishing is performed for a cleaved surface 50 so that the
stock removal of the polishing can be 70-130 nm, preferably about
100 nm.
[0043] After the above processes, a high quality SOI wafer 10
having a SOI layer 25 with high uniformity of film thickness which
is a layer having no crystal defects can be produced.
[0044] Next, as to the method for producing a SOI wafer according
to the method B, in the process 1, two mirror-polished silicon
wafers 22 and 23, which are satisfied with the specification of a
device, are prepared. In the process 2, at least one out of two
wafers, i.e., the wafer 23 is thermally oxidized to form an oxide
film 31 having a thickness of about 0.1-2.0 .mu.m on its surface.
In the process 3, hydrogen ions or rare gas ions are implanted
(hydrogen ions are implanted here) from a surface of the oxide film
31 on the wafer 23 to form a microcavity layer (implanted layer) 41
at an average penetration depth of ions in parallel with its
surface. And its implantation temperature is preferably
25-450.degree. C. The process 4 is the process such that a surface
of the oxide film 31 serving as a hydrogen ion implanted surface of
the hydrogen ion implanted wafer 23 is brought into contact with
the silicon wafer 22, and by contact of each surface of two wafers
under a clean atmosphere at a room temperature, both wafers are
joined without a adhesive agent or the like. Next, after the
processes 5 to 7 conducted by the same processes as the method A, a
SOI wafer with a uniform film thickness which have no crystal
defects can be obtained.
[0045] In the present invention, the ion implantation dosage at the
time when hydrogen ions are implanted into one wafer in the process
3 of the ion implantation delamination method is 5.times.10.sup.16
ions/cm.sup.2 or more and less than 7.5.times.10.sup.16/cm.sup.2.
According to this, a width of a SOI island region in a edge portion
of the SOI wafer, which is easily generated in delamination, can be
reduced to 1 mm or less, and a SOI wafer of which defect density of
LPD existing in a surface of the SOI wafer is extremely reduced can
be produced. Further, when the implantation dosage falls within the
above range, the wafers can be stably delaminated.
[0046] Hereinafter, the present invention will be explained
specifically in reference to the example, but the present invention
is not limited thereto.
EXAMPLE
[0047] By using a MCZ method (Magnetic field applied Czochralski
method) in which crystal was pulled while applying a magnetic
field, a silicon single crystal of which so-called grown-in defects
were reduced was pulled while controlling pulling conditions. The
ingot of the crystal was processed in a normal manner, and
mirror-polished silicon wafers (a diameter of 200 mm, crystal
orientation of <100>, conductive type of p-type, and
resistivity of 10 .OMEGA.cm) of which COPs were reduced in the
whole crystal were produced.
[0048] The surface of the wafers was measured in terms of COP by a
surface inspection apparatus (SP-1, product of KLA-Tencor
Corporation), and it was found that no COP having a diameter of
0.19 .mu.m or more existed. The COP (Crystal Originated Particle)
was a void type defect having a size of about 0.1-0.2 .mu.m, which
is one of grown-in defects.
[0049] Next, based on process conditions below, three SOI wafers
per each condition were produced from the wafers produced above by
an ion implantation delamination method.
[0050] 1) Thickness of a buried oxide film: 145 nm, and Thickness
of a SOI film: 160 nm.
[0051] 2) Conditions of hydrogen ion implantation; Implantation
energy: 56 keV, Dosages: six standards of 4.5.times.10.sup.16,
5.5.times.10.sup.16, 6.5.times.10.sup.16, 7.0.times.10.sup.16,
7.5.times.10.sup.16, and 8.5.times.10.sup.16 ions/cm.sup.2.
[0052] 3) Delamination heat treatment; Temperature: 500.degree. C.,
Time: 30 minutes, and Atmosphere: an inert gas (Ar).
[0053] 4) Bonding heat treatment; Temperature: 1100.degree. C.,
Time: 2 hours.
[0054] 5) Touch polishing; Stock removal: 100 nm.
[0055] After the SOI wafers were produced based on each dosage
described above, the SOI wafers was measured about each SOI island
region width and terrace width by a optical microscope. The results
of the measurements are shown in Table 1 and FIG. 2.
[0056] From these results, it was found that the width of the
region where the SOI islands 42 exist was sharply expanded when the
hydrogen implantation dosage was 7.5.times.10.sup.16 ions /cm.sup.2
or more. Further, when the width of a SOI island region was
expanded, the width of the terrace 43 was also expanded by the same
tendency.
[0057] Further, it was found that when the hydrogen dozage was less
than 5.times.10.sup.16 ions /cm.sup.2, formation of defects and
strength of expansion due to vaporization of hydrogen is not
sufficient since the hydrogen implantation dosage was too small, a
SOI layer was only partially transferred to a base wafer so that
delamination on whole surface of the wafer fell into difficulties,
and therefore a SOI wafer could not be produced.
[0058] According to the above results, in order to narrow the SOI
terrace width and reduce generation of SOI islands in the hydrogen
ion implantation delamination method, the hydrogen implantation
dosage is preferably less than 7.5.times.10.sup.16 ions /cm.sup.2.
Further, when the implantation dosage is less than
7.5.times.10.sup.16 ions /cm.sup.2 and 5.times.10.sup.16 ions
/cm.sup.2 or more, the terrace width and generation of SOI islands
are almost the same level. TABLE-US-00001 TABLE 1 Item Hydrogen ion
implantation SOI island region Exam. dosage width Terrace width No.
[.times.10.sup.16 ions/cm.sup.2] [mm] [mm] 1 4.5 SOI layer could
not be transferred to a base wafer 2 5.5 0.2 2.2 3 6.5 0.3 2.2 4
7.0 0.3 2.2 5 7.5 1.0 2.6 6 8.5 1.5 3.2
[0059] On the other hand, LPD densities in each surface of SOI
wafers produced under the conditions of each dosage were measured
by an optical surface inspection apparatus (SP-1, product of
KLA-Tencor Corporation). The measured size of LPDs was 0.19 .mu.m
or more, and the region in the edge portion which is exclusive was
5 mm. The average of LPD densities in the wafer surfaces in three
standars of the dosages are shown in FIG. 3. It shows that when the
implantation dosage is 7.5.times.10.sup.16 ions /cm.sup.2 or more,
LPDs are sharply increased, and when the implantation dosage is
less than 7.5.times.10.sup.16 ions /cm.sup.2, LPDs are suppressed
at the same level.
[0060] Therefore, in the method of producing a SOI wafer by an ion
implantation delamination method, the hydrogen dosage to be
implanted is preferably 5.times.10.sup.16 ions /cm.sup.2 or more
and less than 7.5.times.10.sup.16 ions /cm.sup.2, more preferably,
5.5.times.10.sup.16 ions /cm.sup.2 or more and less than
7.times.10.sup.16 ions /cm.sup.2.
[0061] The present invention is not limited to the embodiment
described above. The above-described embodiment is a mere example,
and those having substantially the same structure as that described
in the appended claims and providing the similar functions and
advantages are included in the scope of the present invention.
[0062] For example, in the above-described embodiment, it is
explained by exemplifying the case where a silicon single crystal
wafer having a diameter of 8 inches is used. However, the present
invention is not limited thereto and can be applied to the case
where a silicon single crystal wafer having a diameter of 4-16
inches or more is used. Further, the present invention can also be
applied to not only the case of bonding between silicon single
crystal wafers but also the case of bonding between a silicon
single crystal wafer and an insulator substrate (such as quartz,
alumina, sapphire, or silicon carbide).
* * * * *