U.S. patent application number 10/211583 was filed with the patent office on 2003-02-13 for silicon single crystal wafer fabricating method and silicon single crystal wafer.
This patent application is currently assigned to TOSHIBA CERAMICS CO., LTD.. Invention is credited to Fujimori, Hiroyuki, Kashima, Kazuhiko, Kobayashi, Akihiko, Osanai, Junichi, Watanabe, Masayuki.
Application Number | 20030029375 10/211583 |
Document ID | / |
Family ID | 19070942 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030029375 |
Kind Code |
A1 |
Watanabe, Masayuki ; et
al. |
February 13, 2003 |
Silicon single crystal wafer fabricating method and silicon single
crystal wafer
Abstract
At the time of fabricating a silicon single crystal wafer from a
nitrogen-doped silicon single crystal grown according to the
Czochralski method, a silicon single crystal wafer covered with a
region in which an oxygen precipitation bulk micro defect and an
oxidation induced stacking fault mixedly exist is subjected to heat
treatment at a temperature of 1100 to 1300.degree. C. in a reducing
gas or inert gas atmosphere. In such a manner, a method of
fabricating a high-quality silicon single crystal wafer and a
silicon single crystal wafer in which no grown-in crystal defects
exist in the whole surface and oxygen precipitation bulk micro
defects (BMD) are formed at a sufficiently high density to display
the IG effect on the inner side can be provided. The single crystal
wafer can be suitably used to form an operation region of a
semiconductor device.
Inventors: |
Watanabe, Masayuki;
(Hadano-city, JP) ; Osanai, Junichi;
(Nishiokitama-gun, JP) ; Kobayashi, Akihiko;
(Sagamihara-city, JP) ; Kashima, Kazuhiko; (Tokyo,
JP) ; Fujimori, Hiroyuki; (Hadano-city, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
TOSHIBA CERAMICS CO., LTD.
|
Family ID: |
19070942 |
Appl. No.: |
10/211583 |
Filed: |
August 5, 2002 |
Current U.S.
Class: |
117/13 |
Current CPC
Class: |
C30B 15/203 20130101;
C30B 29/06 20130101; C30B 33/00 20130101 |
Class at
Publication: |
117/13 |
International
Class: |
C30B 015/00; C30B
021/06; C30B 027/02; C30B 028/10; C30B 030/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2001 |
JP |
2001-240312 |
Claims
What is claimed is:
1. A silicon single crystal wafer fabricating method of fabricating
a silicon single crystal wafer from a nitrogen-doped silicon single
crystal grown according to the Czochralski method, wherein a
silicon single crystal wafer covered with a region in which an
oxygen precipitation bulk micro defect and an oxidation induced
stacking fault mixedly exist is subjected to heat treatment at a
temperature of 1100 to 1300.degree. C. in a reducing gas or inert
gas atmosphere.
2. The silicon single crystal wafer fabricating method according to
claim 1, wherein at the time of growing said nitrogen-doped silicon
single crystal, a V/G value as a ratio between a pulling rate V
(mm/min) of a single crystal and a temperature gradient G (.degree.
C./mm) in the axial direction of the single crystal where a region
in which both the oxygen precipitation bulk micro defect and an
oxidation induced stacking fault mixedly exist is formed, near a
crystallization interface is preliminarily determined at each
doping nitrogen concentration, and a pulling condition is adjusted
so as to satisfy the V/G value, thereby forming a region in which
an oxygen precipitation bulk micro defect and an oxidation induced
stacking fault mixedly exist in the single crystal.
3. A silicon single crystal wafer fabricated by the silicon single
crystal wafer fabricating method according to claim 1 or 2, wherein
no grown-in crystal defects exist in a surface layer portion having
a depth of at least 10 .mu.m from the surface, and oxygen
precipitation bulk micro defects are formed at a density of
1.times.10.sup.9/cm.sup.3 or higher on the inner side.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of fabricating a
silicon single crystal wafer used for fabricating a semiconductor
device or the like and to a silicon single crystal wafer. More
particularly, the invention relates to a method of fabricating a
silicon single crystal wafer from a nitrogen-doped silicon single
crystal grown according to the Czochralski method and to a silicon
single crystal wafer fabricated by the method.
[0003] 2. Description of the Related Art
[0004] The most common silicon single crystal wafer used for
fabricating a semiconductor device is a one obtained by processing
a single crystal ingot grown according to the Czochralski method
(CZ method).
[0005] According to the CZ method, a single crystal is grown by
dipping a seed crystal in a silicon molten in a crystal crucible,
pulling the seed crystal away from the molten while rotating the
quartz crucible and the seed crystal to grow a cylindrical silicon
single crystal, thereby developing an ingot.
[0006] In a wafer obtained from the silicon single crystal grown by
the CZ method, however, various grown-in crystal defects occur.
[0007] One of the grown-in crystal defects is called an oxidation
induced stacking fault (OSF) which occurs in a ring shape due to a
thermal oxidation process. Since the OSFs occur in a ring shape,
this region is called an OSF ring. The width of the OSF ring is
usually about a few mm to ten mm. The OSF deteriorates a junction
leak characteristic as one of semiconductor device
characteristics.
[0008] Since oxygen precipitation does not easily occur in the
region of the OSF ring, it is difficult to sufficiently form oxygen
precipitation bulk micro defects (hereinbelow, called BMD)
functioning as a gettering site of a heavy metal which is generated
in a semiconductor device fabricating process, that is, IG
(Intrinsic Gettering).
[0009] Since the OSF ring moves toward the peripheral side of the
single crystal as the pulling rate increases, to form the OSF ring
in the outermost periphery of a crystal, high-speed pulling of 1.0
mm/min or higher is performed.
[0010] However, voids defect called COP (Crystal Originated
Particles) exist on the inside of the OSF ring. If nothing is done
for the defects, an oxide film resistance characteristic and a
junction leak characteristic of a semiconductor device
deteriorate.
[0011] Consequently, a method of reducing void defects by
performing heat treatment in a gaseous hydrogen or argon gas
atmosphere is employed.
[0012] On the other hand, a method of reducing a void defect region
by decreasing the pulling speed to 0.5 mm/min or lower to form the
OSF ring in the center of a wafer is also proposed. According to
the method, void defects do not occur in the outer side of the OSF
ring, and an oxide film resistance characteristic is also
excellent.
[0013] In this case, however, dislocation clusters often occur in
the peripheral portion in a wafer. The dislocation clusters also
deteriorate the junction leak characteristic. Further, in this
region, oxygen precipitation does not easily occur, so that the IG
function deteriorates.
[0014] To solve the technical problems, for example, Japanese
Unexamined Patent Application No. 8-330316 discloses a technique
capable of forming avoid-free region in the whole area in the
radial direction of a single crystal on the basis of the knowledge
that a region in which an infrared scattering defect (void), OSF
ring, and dislocation cluster occur can be specified by a ratio
expressed by V/G where V denotes a rate (mm/min) of pulling a
single crystal and G (.degree. C./mm) denotes an average value of
temperature gradient in a crystal in the pulling axis direction in
a high temperature range from a silicon melting point to
1300.degree. C.
[0015] Specifically, the publication discloses a technique capable
of specifying a region including no grow-in crystal defect formed
between an OSF ring and a dislocation cluster occurrence region by
the V/G value and obtaining a silicon single crystal wafer in which
a defect-free region is formed in the whole face by controlling the
V/G value in the crystal axis direction and the radial direction at
the time of growing a crystal to 0.20 to 0.22 mm.sup.2/.degree. C.
min.
[0016] However, in a heat-treated wafer obtained from a single
crystal grown by a high-speed pulling method, even after the heat
treatment, micro void defects each having a size of 0.1 .mu.m or
less tend to remain. Consequently, in order to use a wafer for a
device of a finder design pattern, such a micro void defect has to
be dissipated by performing heat treatment for long time at high
temperature.
[0017] In the case of pulling a single crystal having a larger
diameter of 300 mm or larger, it is difficult to pull the single
crystal at high speed. The pulling rate has to be regulated to an
intermediate rate of 0.5 to 1.0 mm/min at which an OSF ring
remains.
[0018] On the other hand, in the case of growing a defect-free
region at low speed, it is very difficult to control the V/G value
in a narrow range in both of the axial and radial directions of a
single crystal. Moreover, oxygen precipitation easily occurs, so
that it is necessary to add the IG function or the like by another
means. Due to low speed, decrease in productivity is also
caused.
[0019] To deal with such problems, recently, a method of doping a
single crystal with nitrogen at the time of pulling the silicon
single crystal in accordance with the CZ method is being variously
studied.
[0020] For example, it is reported by H. Tamatsuka et al., "DEFECT
IN SILICON III, PV99-1" p. 456 that by doping a single crystal with
nitrogen, the size of avoid defect is reduced. As a result, by a
high-temperature heat treatment in a gaseous hydrogen or argon gas
atmosphere, the void defect is easily dissipated. A surface layer
portion without a void defect from the surface of the wafer to the
depth of 10 .mu.m or more is formed.
[0021] However, in order to sufficiently and reliably form such a
surface layer portion, oxygen concentration in the crystal has to
be suppressed. In this case, it becomes difficult to form BMDs
functioning as a getter site at a density of
1.times.10.sup.9/cm.sup.3 or higher.
[0022] Consequently, only by a single crystal pulled at a high
speed of 1.8 mm/min under an oxygen concentration condition of a
very narrow range, both the front layer portion and the BMD can be
formed. It cannot be said that the method is sufficient as an
industrial wafer fabricating method, and there is a room to
improve.
[0023] It is reported by M. Iida et al., "DEFECT IN SILICON III,
PV99-1" p. 499 that, by doping a single crystal with nitrogen, a
defect-free region is expanded, that is, the range of the V/G value
of the defect-free region is widened. Simultaneously, a region in
which the OSF ring occurs also expands. However, the OSF ring can
be made disappear by lowering the oxygen concentration and, by the
amount, the V/G value shifts to a larger value and the defect-free
region expands.
[0024] As described above, by doping a single crystal with
nitrogen, it becomes easier to form a defect-free region. However,
it is still difficult to form a sufficient amount of BMDs in the
defect-free region. Particularly, it is difficult to form BMDs in a
wafer of low oxygen concentration.
SUMMARY OF THE INVENTION
[0025] The present invention has been achieved to solve the
technical problems, and its object is to provide a silicon single
crystal wafer fabricating method capable of obtaining a
high-quality wafer having no grown-in crystal defects in an entire
surface, in which BMDs are formed at a sufficiently high density on
the inner side to display an IG effect.
[0026] Another object is to provide a silicon single crystal wafer
suitable for forming an operation region of a semiconductor device,
having excellent reliability and a junction leak characteristic of
a gate oxide film by the fabricating method.
[0027] According to the invention, there is provided a silicon
single crystal wafer fabricating method of fabricating a silicon
single crystal wafer from a nitrogen-doped silicon single crystal
grown according to the Czochralski method, characterized in that a
silicon single crystal wafer covered with a region (M-band) in
which an oxygen precipitation bulk micro defect (BMD) and an
oxidation induced stacking fault (OSF) mixedly exist is subjected
to heat treatment at a temperature of 1100 to 1300.degree. C. in a
reducing gas or inert gas atmosphere.
[0028] According to the invention, by annealing the wafer covered
with the M-band obtained from the nitrogen-doped silicon single
crystal at high temperature in a reducing or inert gas atmosphere,
a wafer in which the OSF and BMD in the surface layer portion are
reduced and BMDs are formed on the inner side at a sufficiently
high density to display the IG effect is obtained.
[0029] Preferably, at the time of growing the nitrogen-doped
silicon single crystal, a V/G value as a ratio between a pulling
rate V (mm/min) of a single crystal and a temperature gradient G
(.degree. C./mm) in the axial direction of the single crystal where
a region (M-band) in which both the oxygen precipitation bulk micro
defect (BMD) and an oxidation induced stacking fault (OSF) mixedly
exist is formed, near a crystallization interface is preliminarily
determined at each doping nitrogen concentration, and a pulling
condition is adjusted so as to satisfy the V/G value, thereby
forming a region (M-band) in which an oxygen precipitation bulk
micro defect (BMD) and an oxidation induced stacking fault (OSF)
mixedly exist in the single crystal.
[0030] Since the M-band is specified by the V/G value, by the
fabricating method, a silicon single crystal ingot in which the
M-band is formed in a wide range in the core portion can be
obtained reliably and easily. Thus, a wafer in which no grown-in
defects exists in the surface layer portion but the BMDs are formed
on the inner side at a sufficiently high density to produce the IG
effect can be mass produced at a high yield.
[0031] According to the invention, there is also provided a silicon
single crystal wafer fabricated by the silicon single crystal wafer
fabricating method, characterized in that no grown-in crystal
defects exist in a surface layer portion having a depth of at least
10 .mu.m from the surface, and oxygen precipitation bulk micro
defects (BMD) are formed at a density of 1.times.10.sup.9/cm.sup.3
or higher on the inner side.
[0032] Such a silicon single crystal wafer has excellent
reliability of a gate oxide film and excellent junction leak
characteristic and can be suitably used for forming an operation
region of a semiconductor device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention will be described in more detail with
reference to the attached drawings.
[0034] FIGS. 1A and 1B are longitudinal cross sections
schematically each showing the relation between V/G and a defect
distribution in a silicon single crystal in the case where the
silicon single crystal is not doped with nitrogen (FIG. 1A) and in
the case where the silicon single crystal is doped with nitrogen
(FIG. 1B);
[0035] FIGS. 2A to 2C are diagrams showing in-plane distributions
of BMD and OSF of wafers taken along lines A-A (FIG. 2A), B-B (FIG.
2B), and E-E (FIG. 2C), respectively, of the nitrogen-doped silicon
single crystal of FIG. 1B; and
[0036] FIG. 3 is a diagram showing the correlation between nitrogen
concentration of a nitrogen-doped silicon single crystal and V/G
values of various grown-in crystal defect generating region.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0037] The invention will be described more specifically
hereinbelow with reference to the drawings.
[0038] FIGS. 1A and 1B are longitudinal cross sections each
schematically showing the relation between a ratio V/G between a
pulling ratio V of a silicon single crystal a temperature gradient
G in the axial direction of the single crystal near a
crystallization interface and a defect distribution in a
longitudinal section direction of the single crystal. FIG. 1A shows
the case where the silicon single crystal is not doped with
nitrogen and FIG. 1B shows the case where the silicon single
crystal is doped with nitrogen.
[0039] The nitrogen concentration in the silicon single crystal is
2.times.10.sup.14 atoms/cm.sup.3, and the oxygen concentration is
1.2.times.10.sup.16 atoms/cm.sup.3. The oxygen concentration in the
invention is expressed by a value obtained by a conversion factor
according to the old ASTM.
[0040] FIGS. 2A to 2C are diagrams showing in-plane distributions
of BMD and OSF of wafers taken along lines A-A (FIG. 2A), B-B (FIG.
2B), and E-E (FIG. 2C), respectively, of the nitrogen-doped silicon
single crystal of FIG. 1B.
[0041] As shown in FIGS. 1A and 1B, in the case of growing a single
crystal while decreasing the pulling rate V, that is, changing the
V/G value so as to decrease, in both of the case where the single
crystal is not doped with nitrogen (FIG. 1A) and the case where the
single crystal is doped with nitrogen (FIG. 1B), occurrence of
grown-in crystal defects changes like a void defect occurrence
region 1, an OSF ring occurrence region 2 and, while sandwiching a
defect-free region 3, a dislocation cluster occurrence region
4.
[0042] As understood by comparing FIGS. 1A and 1B with each other,
by the nitrogen doping, the OSF ring occurrence region 2 and the
defect-free region 3 are expanded.
[0043] As described above, in the OSF ring occurrence region,
although no void defect occurs, it is difficult to form a BMD.
Consequently, it is considered that a wafer obtained in the region
is not adapted as a wafer for a semiconductor device.
[0044] However, as understood from FIG. 2A showing the in-plane
distribution of the OSF and BMD of the wafer taken along line A-A
of FIG. 1B, in the OSF ring occurrence region 2, in reality, a
region 2b in which many BMDs are formed (hereinbelow, called an
M-band) is formed on the outside of a region 2a in which a small
amount of BMDs is formed (hereinbelow, called a P-band). The OSF
ring occurrence region 2 is divided into the two regions.
[0045] Particularly, in the nitrogen-doped single crystal as shown
in FIG. 1B, the P-band 2a is narrow whereas the M-band 2b expands
to the outside of the P-band 2a where the V/G value is small.
[0046] Since the wafer taken along line B-B of FIG. 1B corresponds
to the M-band 2b, as shown in FIG. 2B, BMDs occur at a density of
1.times.10.sup.9/cm.sup.3 or higher uniformly in the entire plane
of the wafer. The wafers taken along line C-C and line D-D of FIG.
1B are similar to the wafer.
[0047] The wafer taken along line E-E of FIG. 1B corresponds to the
defect-free region 3. Consequently, as shown in FIG. 2C, although
no OSF occurs, the BMDs are formed at a density less than
1.times.10.sup.7/cm.sup.3. The density is not high enough.
[0048] According to the invention, a nitrogen-doped silicon single
crystal is grown under the condition that the M-band in which the
OSF and BMD mixedly exist is formed in a wide range, a wafer
covered with the M-band obtained from the single crystal is
subjected to high-temperature annealing in a reducing gas or inert
gas atmosphere, thereby obtaining a wafer in which the OSF and BMD
are reduced in the region from the surface to the depth of 10 .mu.m
or deeper and BMDs are formed at a sufficiently high density of
1.times.10.sup.9/cm.sup.3 or higher on the inside to display the IG
effect.
[0049] As described above, the M-band is a region where void
defects do not originally occur. Therefore, by performing the
high-temperature annealing, a silicon single crystal wafer in which
no grown-in crystal defect exists from the surface to the depth of
10 .mu.m or deeper, suitable for forming an operation region of a
semiconductor device can be obtained.
[0050] Although the concentration of doped nitrogen of the
nitrogen-doped silicon single crystal according to the invention is
not particularly limited, from a viewpoint of forming a wide M-band
or the like, it is preferably in a range from about
0.5.times.10.sup.14 to 5.times.10.sup.14 atoms/cm.sup.3.
[0051] Preferably, the oxygen concentration is usually, from a
viewpoint of forming BMDs at a sufficiently high density, in a
range from about 0.8.times.10.sup.16 to 1.4.times.10.sup.18
atoms/cm.sup.3.
[0052] The M-band is specified by the V/G value, that is, the ratio
between the pulling rate V (mm/min) of the single crystal and a
temperature gradient G (.degree. C./mm) in the axial direction of
the single crystal near the crystallization interface.
[0053] FIG. 3 is a diagram showing the correlation between the
nitrogen concentration in the nitrogen-doped silicon single crystal
and the V/G values in various grown-in crystal defect occurrence
regions. It shows the case where the concentration of oxygen is
1.2.times.10.sup.18 atoms/cm.sup.3.
[0054] Since each of the V/G values corresponding to the various
grown-in crystal defects occurrence regions changes according to
the nitrogen concentration and oxygen concentration in the single
crystal to be grown, it is preferable to preliminarily obtain the
correlation between the M-band associated with the change in the
concentration of nitrogen and the V/G value as shown in FIG. 3 and
adjust V and/or G on the basis of the correlation to grow a single
crystal.
[0055] In a practical oxygen concentration range from
0.8.times.10.sup.18 to 1.4.times.10.sup.18 atoms/cm.sup.3, a change
in the V/G value in the M-band in accordance with oxygen
concentration is very small.
[0056] By using evaluation of a BMD precipitation distribution as
shown in FIG. 2 at the time of specifying the M-band, the M-band
can be specified reliably and easily.
[0057] In the invention, in such a manner, the single crystal is
grown by determining the range of the V/G value to form the M-band
and adjusting the single crystal pulling rate V and the temperature
gradient G in the axial direction of the single crystal near the
crystallization interface so as to satisfy the V/G value.
[0058] Consequently, a silicon single crystal ingot in which the
M-band is formed in a wide range in the core portion can be
obtained reliably and easily. Thus, a wafer in which no OSF and BMD
exists in the surface layer portion and BMDs are formed at a
sufficiently high density to display the IG effect on the inner
side can be mass produced at a high yield.
[0059] Specifically, for example, a predetermined amount of
polysilicon of high impurity is charged into a quartz crucible and
melted and, by using the nitrogen concentration and oxygen
concentration as parameters, a single crystal having a
predetermined diameter is grown so that the V/G value decreases
from the head toward the tail.
[0060] In this case, the G value can be obtained from analysis of
heat transmission by a computer, and the M-band is determined on
the basis of the BMD precipitation evaluation as described
above.
[0061] A wafer covered with the M-band is fabricated from the
silicon single crystal ingot and subjected to annealing at high
temperature in a reducing or inert gas atmosphere.
[0062] In the annealing, it is preferable to use hydrogen, ammonia,
or the like as a reducing gas and to use argon, helium, neon, or
the like as an inert gas. More preferably, a hydrogen gas or argon
gas is used. In such a gas atmosphere, the wafer is treated for
about 0.5 to 3 hours at a high temperature in a range from 1100 to
1300.degree. C., preferably, at about 1200.degree. C.
[0063] According to the fabricating method, the silicon single
crystal wafer in which no grown-in crystal defect exists in the
surface portion from the surface to the depth of at least 10 .mu.m,
and BMDs are formed at a sufficiently high density of
1.times.10.sup.9/cm.sup.3 or higher to display the IG effect on the
inner side can be obtained. Such a silicon single crystal wafer can
be suitably used to form an operation region of a semiconductor
device.
Examples
[0064] The invention will be described hereinbelow more concretely
on the basis of examples. The invention is not limited to the
examples.
[0065] 250 kg of high-purity polysilicon was charged into a 32-inch
quartz crucible. <100> Crystal of 12 inches was grown by
using a nitrogen concentration and an oxygen concentration as
parameters so that the V/G value decreases from the head toward the
tail, thereby obtaining a nitrogen-doped silicon single
crystal.
[0066] With respect to a wafer and a longitudinal section sample
obtained from the single crystal, the correlation of the grown-in
crystal defects and the V/G value was evaluated. The G value was
obtained from the heat transmission analysis by a computer. The
M-band was specified by the BMD precipitation evaluation.
[0067] From the relation between the grown-in crystal defect and
the V/G value, the V/G value of the M-band under predetermined
growth conditions (the nitrogen and oxygen concentrations) was
determined.
[0068] As a result, in the case where the nitrogen concentration is
2.times.10.sup.14 atoms/cm.sup.3 and the oxygen concentration is
1.2.times.10.sup.18 atoms/cm.sup.3, it was found that the V/G value
of the M-band lies in the range from 0.275 to 0.215
mm.sup.2/.degree. C. min. It is understood from the result of heat
transmission analysis that the G value changes from 3.degree. C./mm
at the head toward 2.degree. C./mm at the tail.
[0069] Therefore, the silicon single crystal was grown while
adjusting, according to the pulling conditions, the pulling rate to
0.825 to 0.645 mm/min on the head side and to 0.550 to 0.430 mm/min
on the tail side.
[0070] As a result, a silicon single crystal ingot in which the
M-band is formed in a wide range from the head to the tail was
grown, and a silicon single crystal wafer covered with the M-band
was obtained from the single crystal ingot.
[0071] Further, the obtained wafer was subjected to annealing at
1200.degree. C. for one hour in a gaseous hydrogen atmosphere. As a
result, a high-quality wafer having no grown-in crystal defects in
the surface layer portion having a depth of at least 10 .mu.m from
the surface but having, on the inner side, BMDs which are uniformly
formed at 1.times.10.sup.9/cm.sup.3 or higher was obtained.
[0072] A wafer was obtained from a portion adjacent to the portion
from which the wafer subjected to the hydrogen annealing was taken
in the single crystal ingot. The wafer was annealed at 1200.degree.
C. for two hours in an argon gas atmosphere.
[0073] In this case as well, a high-quality wafer similar to the
wafer subjected to the hydrogen annealing was obtained.
[0074] As described above, by the fabricating method according to
the invention, a high-quality silicon single crystal wafer in which
harmful grown-in crystal defects such as OSF, void defect, and
dislocation cluster do not exist in the whole surface layer portion
and, on the inner side, BMDs are formed at a sufficiently high
density to display the IG effect can be obtained reliably and
easily.
[0075] The silicon single crystal wafer according to the invention
has excellent reliability of a gate oxide film and an excellent
junction leak characteristic and can be suitably used for forming
an operation region of a semiconductor device. By using the wafer
for a finer circuit device having a higher packing density, the
device characteristics and manufacturing yield of the device can be
improved.
* * * * *