U.S. patent application number 17/705999 was filed with the patent office on 2022-07-14 for silicon carbide ingot manufacturing method and silicon carbide ingot manufactured thereby.
This patent application is currently assigned to SENIC INC.. The applicant listed for this patent is SENIC INC.. Invention is credited to Jung Woo CHOI, Jung-Gyu KIM, Kap-Ryeol KU, Jong Hwi PARK, Jung Doo SEO.
Application Number | 20220220632 17/705999 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-14 |
United States Patent
Application |
20220220632 |
Kind Code |
A1 |
PARK; Jong Hwi ; et
al. |
July 14, 2022 |
SILICON CARBIDE INGOT MANUFACTURING METHOD AND SILICON CARBIDE
INGOT MANUFACTURED THEREBY
Abstract
A silicon carbide ingot manufacturing method and a silicon
carbide ingot manufacturing system are provided. The silicon
carbide ingot manufacturing method and the silicon carbide ingot
manufacturing system may change a temperature gradient depending on
the growth of an ingot by implementing a guide which has a tilted
angle to an external direction from the interior of a reactor, in
an operation to grow an ingot during a silicon carbide ingot
manufacturing process.
Inventors: |
PARK; Jong Hwi; (Cheonan-si,
KR) ; KU; Kap-Ryeol; (Cheonan-si, KR) ; KIM;
Jung-Gyu; (Cheonan-si, KR) ; CHOI; Jung Woo;
(Cheonan-si, KR) ; SEO; Jung Doo; (Cheonan-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SENIC INC. |
Cheonan-si |
|
KR |
|
|
Assignee: |
SENIC INC.
Cheonan-si
KR
|
Appl. No.: |
17/705999 |
Filed: |
March 28, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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17408727 |
Aug 23, 2021 |
11339497 |
|
|
17705999 |
|
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International
Class: |
C30B 23/00 20060101
C30B023/00; C30B 23/06 20060101 C30B023/06; C30B 29/36 20060101
C30B029/36 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2020 |
KR |
10-2020-0110065 |
Nov 27, 2020 |
KR |
10-2020-0162868 |
Claims
1. A silicon carbide ingot, comprising: a front region and a rear
region which is an opposite surface of the front region, wherein
the rear region is a surface cut from a silicon carbide seed
crystal, wherein the silicon carbide ingot comprises a maximum
height equal to or greater than 15 mm in a direction perpendicular
to the rear region, wherein the silicon carbide ingot has a ratio,
Df/Db, of 0.95 to 1.17, wherein Db is a diameter of the rear region
and Df is a diameter of a circumference of the front region,
wherein the silicon carbide ingot has an angle of -4.degree. to
50.degree. between a line perpendicular to the rear region from one
side of the circumference of the rear region, and an edge line
linking one side of the front region, which is close to the one
side of the circumference of the rear region, from a plane
comprising the line perpendicular to the rear region from one side
of the circumference of the rear region and the diameter of the
rear region.
2. The silicon carbide ingot of claim 1, wherein the silicon
carbide ingot manufactured by the silicon carbide ingot
manufacturing device comprises a front region and a rear region
which is an opposite surface front region, wherein the rear region
is a surface cut from a silicon carbide seed crystal, wherein the
silicon carbide ingot has a maximum height equal to or greater than
15 mm in a perpendicular direction to the rear region, wherein the
silicon carbide ingot has a ratio, Df/Db, of 0.95 to 1.17, wherein
Db is a diameter of the rear region, and the Df is a diameter of
the circumference of the front region, and wherein the silicon
carbide ingot has an angle of -4.degree. to 50.degree. between a
line perpendicular to the rear region from one side of the
circumference of the rear region, and an edge line linking one side
of the front region which is close to the one side of the
circumference of the rear region from a plane comprising the line
perpendicular to the rear region from one side of the circumference
of the rear region and a diameter of the rear region.
3. The silicon carbide ingot of claim 1, wherein the angle of
inclination of the guide is 4.degree. to 25.degree..
4. The silicon carbide ingot of claim 1, wherein the guide that
surrounds the circumferential surface of the silicon carbide seed
crystal has a height equal to or greater that 30 mm, based on a
direction connecting one side of the silicon carbide seed crystal
and the silicon carbide raw material in a shortest distance.
Description
[0001] This application is divisional of U.S. patent application
Ser. No. 17/408,727 filed Aug. 23, 2021, which claims the benefit
under 35 USC 119(a) of Korean Patent Application No.
10-2020-0110065 filed on Aug. 31, 2020, and Korean Patent
Application No. 10-2020-0162868, filed on Nov. 27, 2020, in the
Korean Intellectual Property Office, the entire disclosures of
which are incorporated herein by reference for all purposes.
BACKGROUND
1. Field
[0002] The following disclosure relates to a silicon carbide ingot
manufacturing method, and a silicon carbide manufactured according
to the method.
2. Description of Related Art
[0003] Silicon carbide (SiC) has excellent heat resistance and
mechanical strength, and is physically and chemically stable, so
that it is beneficial as a semiconductor material. Recently, as a
substrate for high power devices, the demand of silicon carbide
single crystal substrates has increased.
[0004] As a method for preparing a silicon carbide single crystal,
there are Liquid Phase Epitaxy (LPE), Chemical Vapor Deposition
(CVD), Physical Vapor Transport (PVT), and similar methods. Among
them, the PVT is a method of growing a silicon carbide single
crystal as follows: loads a silicon carbide raw material into a
crucible, disposes a seed crystal composed of a silicon carbide
single crystal on the top of the crucible, and then heat the
crucible by an induction heating method to sublimate the raw
material to grow the silicon carbide single crystal on the seed
crystal.
[0005] PVT is the most widely used for the preparation of silicon
carbide in the form of an ingot because it has a high growth rate.
However, the temperature distribution inside a crucible may change
depending on the temperature gradient condition during induction
heating of the crucible, the relative position of a heater, the
temperature difference between the top of the crucible and the
bottom of the crucible, etc., thereby affecting the quality of the
manufactured silicon carbide ingot.
[0006] Accordingly, in order to improve the crystal quality of the
silicon carbide ingot and secure the reproducibility of
manufacturing the ingot, it is beneficial to sufficiently consider
factors that may affect the temperature distribution inside the
crucible during ingot growing procedure.
[0007] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention, and therefore it may contain information that does not
form the related art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY
[0008] This Summary is provided to introduce a selection of
concepts in simplified form that are further described below in the
Detailed Description. This Summary is not intended to identify key
features or essential features of the claimed subject matter, nor
is it intended to be used as an aid in determining the scope of the
claimed subject matter.
[0009] In a general aspect, a silicon carbide ingot manufacturing
method includes a preparation operation of disposing a silicon
carbide raw material and a silicon carbide seed crystal in an
internal space of a reactor, and adjusting the internal space of
the reactor to a vacuum atmosphere; a proceeding operation of
injecting an inert gas into the internal space of the reactor,
sublimating the silicon carbide raw material in the internal space
of the reactor through a heater configured to surround the reactor,
and configured to induce a silicon carbide ingot to be grown; and a
cooling operation of cooling a temperature of the internal space of
the reactor to room temperature, cutting a rear region of the
silicon carbide ingot in contact with the seed crystal to retrieve
the silicon carbide ingot; wherein the internal space of the
reactor comprises a guide disposed to surround a circumferential
surface of the silicon carbide seed crystal with a predetermined
interval, wherein the guide is configured to extend toward a
direction that faces a silicon carbide raw material from the
silicon carbide seed crystal, the guide is configured to have a
guide angle of inclination which is tilted to an external side of
the silicon carbide seed crystal by -4.degree. to 50.degree. when a
virtual reference line connecting one side of the silicon carbide
seed crystal and the silicon carbide raw material in a shortest
distance is designated as 0.degree., wherein the proceeding
operation comprises a procedure in which the heater is moved, and
wherein the moving of the heater comprises moving the heater to a
relative position which becomes more distant at a rate of 0.1 mm/hr
to 0.48 mm/hr based on the silicon carbide seed crystal, wherein
the silicon carbide ingot comprises a front region and the rear
region, the silicon carbide ingot has a maximum height equal to or
greater than 15 mm in a direction perpendicular to the rear region,
the silicon carbide ingot has a ratio, Df/Db, of 0.95 to 1.17,
wherein Db is a diameter of the rear region, and Df is a diameter
of the circumference of the front region, and the silicon carbide
ingot has an angle of -4.degree. to 50.degree. between a line
perpendicular to the rear region from one side of the circumference
of the rear region, and an edge line linking one side of the front
region, which is close to the one side of the circumference of the
rear region, from a plane comprising the line perpendicular to the
rear region from one side of the circumference of the rear region
and the diameter of the rear region.
[0010] The angle of inclination of the guide may be 4.degree. to
25.degree..
[0011] The reactor may include a heat insulating material
configured to surround an external surface of the reactor, the heat
insulating material may include a heat insulating circumference
part that surrounds a circumferential surface of the reactor, and a
volume of the reactor Vc and a volume of the heat insulating
circumference part Vi may have a ratio Vc/Vi of 0.05 to 0.8.
[0012] The guide that surrounds the circumferential surface of the
silicon carbide seed crystal may have a height equal to or greater
that 30 mm, based on a direction connecting one side of the silicon
carbide seed crystal and the silicon carbide raw material in a
shortest distance.
[0013] The proceeding operation may sequentially include a
pre-growth process and a growth process, the pre-growth process may
sequentially include a first process, a second process, and a third
process, the first process changes the vacuum atmosphere of the
preparation operation to an inert atmosphere, the second process
raises the temperature of the internal space of the reactor with
the heater, and the third process depressurizes a pressure of the
internal space of the reactor to reach a growth pressure based on
the heating of the internal space of the reactor so that the
temperature of the internal space of the reactor reaches the growth
temperature, the growth process may be a process of maintaining the
internal space of the reactor at the growth temperature and the
growth pressure, and inducing the ingot to grow, a moving of the
heater may be performed in the growth process, wherein a
temperature difference may be a difference between an upper
temperature of the internal space of the reactor and a lower
temperature of the internal space of the reactor, and wherein the
temperature difference in the growth process is 110.degree. C. to
160.degree. C.
[0014] The proceeding operation may sequentially include a
pre-growth process and a growth process, the pre-growth process may
sequentially include a first process, a second process, and a third
process, the first process changes the vacuum atmosphere of the
preparation operation to an inert atmosphere, the second process
raises the temperature of the internal space of the reactor with
the heater, and the third process depressurizes a pressure of the
internal space of the reactor to reach a growth pressure based on a
heating of the internal space of the reactor so that the
temperature of the internal space of the reactor reaches a growth
temperature, the growth process may be a process of maintaining the
internal space of the reactor at the growth temperature and the
growth pressure, and inducing the ingot to grow, a moving of the
heater may be performed in the growth process, a temperature
difference may be a difference between an upper temperature of the
internal space of the reactor and a lower temperature of the
internal space of the reactor, and the temperature difference in
the growth process is 160.degree. C. to 240.degree. C.
[0015] The heat insulating circumference part of the heat
insulating material may have a thickness of 200 mm to 600 mm.
[0016] In a general aspect, a silicon carbide ingot includes a
front region and a rear region which is an opposite surface of the
front region, wherein the rear region is a surface cut from a
silicon carbide seed crystal, wherein the silicon carbide ingot
includes a maximum height equal to or greater than 15 mm in a
direction perpendicular to the rear region, wherein the silicon
carbide ingot has a ratio, Df/Db, of 0.95 to 1.17, wherein Db is a
diameter of the rear region and Df is a diameter of a circumference
of the front region, wherein the silicon carbide ingot may have an
angle of -4.degree. to 50.degree. between a line perpendicular to
the rear region from one side of the circumference of the rear
region, and an edge line linking one side of the front region,
which may be close to the one side of the circumference of the rear
region, from a plane comprising the line perpendicular to the rear
region from one side of the circumference of the rear region and
the diameter of the rear region. In a general aspect, a silicon
carbide ingot manufacturing device includes a reactor, configured
to have an internal space; a heat insulating material, disposed in
an external surface of the reactor, and configured to surround the
reactor; and a heater, configured to adjust one or more of a
temperature of the reactor, and the internal space of the reactor,
wherein the silicon carbide ingot manufacturing device includes a
silicon carbide seed crystal located at an upper portion of the
internal space of the reactor, wherein the silicon carbide ingot
manufacturing device includes a silicon carbide raw material
located at a lower portion of the internal space of the reactor,
and wherein the silicon carbide ingot manufacturing device includes
a mover, configured to change a relative position to an up-and-down
direction between the heater and the reactor, wherein the internal
space of the reactor includes a guide disposed to surround a
circumferential surface of the silicon carbide seed crystal with a
predetermined interval, wherein the guide may be configured to
extend toward a direction that faces the silicon carbide raw
material from the silicon carbide seed crystal, the guide may be
configured to have a guide angle of inclination which is tilted to
an external side of the silicon carbide seed crystal by -4.degree.
to 50.degree. when a virtual reference line connecting one side of
the silicon carbide seed crystal and the silicon carbide raw
material in a shortest distance is designated as 0.degree., wherein
the silicon carbide ingot manufacturing device may be configured to
grow a silicon carbide ingot from the silicon carbide seed crystal,
wherein the silicon carbide ingot manufactured by the silicon
carbide ingot manufacturing device includes a front region and a
rear region which is an opposite surface front region, wherein the
rear region is a surface cut from a silicon carbide seed crystal,
wherein the silicon carbide ingot may have a maximum height equal
to or greater than 15 mm in a perpendicular direction to the rear
region, wherein the silicon carbide ingot may have a ratio, Df/Db,
of 0.95 to 1.17, wherein Db is a diameter of the rear region, and
the Df is a diameter of the circumference of the front region, and
wherein the silicon carbide ingot has an angle of -4.degree. to
50.degree. between a line perpendicular to the rear region from one
side of the circumference of the rear region, and an edge line
linking one side of the front region which is close to the one side
of the circumference of the rear region from a plane comprising the
line perpendicular to the rear region from one side of the
circumference of the rear region and a diameter of the rear
region.
[0017] The temperature of the heater during movement of the heater
may be 2100.degree. C. to 2500.degree. C. based on a maximum
heating region, the maximum heating region may be an internal
region of the heater which has a predetermined length from a center
of the heater to first and second ends of the heater, based on an
arbitrary line linking the silicon carbide raw material and the
silicon carbide seed crystal, the internal space of the reactor may
include a sub-heating region located at an upper portion of the
reactor, the sub-heating region may be an internal region of the
heater which has a predetermined length from the center of the
heater to the first and second ends of the heater, based on an
arbitrary line linking the silicon carbide raw material and the
silicon carbide seed crystal, and a temperature of the sub-heating
region may be lower than a temperature of a maximum heating region
by 110.degree. C. to 160.degree. C.
[0018] The heat insulating material may include a heat material
circumference part configured to surround an external surface of
the reactor, and a volume of the reactor Vc and a volume of the
heat insulating material circumference part Vi may have a ratio,
Vc/Vi, of 0.05 to 0.8.
[0019] Other features and aspects will be apparent from the
following detailed description, the drawings, and the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a conceptual view illustrating a silicon carbide
ingot manufacturing system, in accordance with one or more
embodiments.
[0021] FIG. 2 is a graph illustrating a change of a temperature, a
pressure, and an inert gas (Ar) depending on a time flow, in
accordance with one or more embodiments.
[0022] FIG. 3 is a conceptual view illustrating a system
(manufacturing device) for manufacturing a silicon carbide ingot,
in accordance with one or more embodiments.
[0023] FIG. 4 is a conceptual view illustrating an example reactor
of a system (manufacturing device) for manufacturing a silicon
carbide ingot, in accordance with one or more embodiments.
[0024] FIG. 5 is a conceptual view illustrating an example reactor
of a system (manufacturing device) for manufacturing a silicon
carbide ingot according to other embodiments, approximately,
[0025] FIG. 6 is a conceptual view illustrating a silicon carbide
ingot, in accordance with one or more embodiments.
[0026] FIG. 7 is an image map illustrating micropipe defects in one
side of a silicon carbide wafer of Examples A to D.
[0027] FIG. 8 is an image map illustrating micropipe defects in one
side of a silicon carbide wafer of Comparative Examples A and
B.
[0028] FIG. 9 is a disassembled perspective view illustrating one
example of a reactor, a cover, a heat insulating material, and a
heat insulating material circumference part of a manufacturing
device for a silicon carbide ingot, in accordance with one or more
embodiments.
[0029] FIG. 10 is a perspective view illustrating another example
of a silicon carbide ingot manufacturing device, in accordance with
one or more embodiments.
[0030] FIG. 11 is a perspective view illustrating another example
of a silicon carbide ingot manufacturing device, in accordance with
one or more embodiments.
[0031] FIG. 12 is a conceptual view illustrating sections of an
example reactor and a heat insulating circumference part when
observed at a plane including AA'.
[0032] FIG. 13 is a conceptual view illustrating one example of a
silicon carbide wafer, in accordance with one or more
embodiments.
[0033] Throughout the drawings and the detailed description, the
same reference numerals refer to the same elements. The drawings
may not be to scale, and the relative size, proportions, and
depiction of elements in the drawings may be exaggerated for
clarity, illustration, and convenience.
DETAILED DESCRIPTION
[0034] The following detailed description is provided to assist the
reader in gaining a comprehensive understanding of the methods,
apparatuses, and/or systems described herein. However, various
changes, modifications, and equivalents of the methods,
apparatuses, and/or systems described herein will be apparent after
an understanding of the disclosure of this application. For
example, the sequences of operations described herein are merely
examples, and are not limited to those set forth herein, but may be
changed as will be apparent after an understanding of the
disclosure of this application, with the exception of operations
necessarily occurring in a certain order. Also, descriptions of
features that are known after an understanding of the disclosure of
this application may be omitted for increased clarity and
conciseness, noting that omissions of features and their
descriptions are also not intended to be admissions of their
general knowledge.
[0035] The features described herein may be embodied in different
forms, and are not to be construed as being limited to the examples
described herein. Rather, the examples described herein have been
provided merely to illustrate some of the many possible ways of
implementing the methods, apparatuses, and/or systems described
herein that will be apparent after an understanding of the
disclosure of this application.
[0036] Throughout the specification, when an element, such as a
layer, region, or substrate, is described as being "on," "connected
to," or "coupled to" another element, it may be directly "on,"
"connected to," or "coupled to" the other element, or there may be
one or more other elements intervening therebetween. In contrast,
when an element is described as being "directly on," "directly
connected to," or "directly coupled to" another element, there can
be no other elements intervening therebetween.
[0037] As used herein, the term "and/or" includes any one and any
combination of any two or more of the associated listed items.
[0038] Although terms such as "first," "second," and "third" may be
used herein to describe various members, components, regions,
layers, or sections, these members, components, regions, layers, or
sections are not to be limited by these terms. Rather, these terms
are only used to distinguish one member, component, region, layer,
or section from another member, component, region, layer, or
section. Thus, a first member, component, region, layer, or section
referred to in examples described herein may also be referred to as
a second member, component, region, layer, or section without
departing from the teachings of the examples.
[0039] Spatially relative terms such as "above," "upper," "below,"
and "lower" may be used herein for ease of description to describe
one element's relationship to another element as shown in the
figures. Such spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. For example,
if the device in the figures is turned over, an element described
as being "above" or "upper" relative to another element will then
be "below" or "lower" relative to the other element. Thus, the term
"above" encompasses both the above and below orientations depending
on the spatial orientation of the device. The device may also be
oriented in other ways (for example, rotated 90 degrees or at other
orientations), and the spatially relative terms used herein are to
be interpreted accordingly.
[0040] The terminology used herein is for describing various
examples only, and is not to be used to limit the disclosure. The
articles "a," "an," and "the" are intended to include the plural
forms as well, unless the context clearly indicates otherwise. The
terms "comprises," "includes," and "has" specify the presence of
stated features, numbers, operations, members, elements, and/or
combinations thereof, but do not preclude the presence or addition
of one or more other features, numbers, operations, members,
elements, and/or combinations thereof.
[0041] The features of the examples described herein may be
combined in various ways as will be apparent after an understanding
of the disclosure of this application. Further, although the
examples described herein have a variety of configurations, other
configurations are possible as will be apparent after an
understanding of the disclosure of this application.
[0042] In this application, the phrase "combination(s) thereof"
included in a Markush-type expression denotes one or more mixtures
or combinations selected from the group consisting of components
stated in the Markush-type expression, that is, denotes that one or
more components selected from the group consisting of the
components are included.
[0043] In this application, a size and an angle illustrated in
drawings are arbitrarily shown for easy description, and are not
necessarily analyzed by being limited to the illustration.
[0044] In this application, a silicon carbide wafer refers to a
silicon carbide wafer before formation of a so-called epitaxial
layer which is a single crystal layer having a directivity
(so-called bear wafer).
[0045] While the inventors consider a plan to minimize the
occurrence of defects and cracks in the silicon carbide ingot and
improve the silicon carbide ingot crystal quality, the inventors
invented a method of manufacturing a silicon carbide ingot in which
a guide unit is equipped inside a reactor that controls the shape
of a silicon carbide ingot and the relative position of the heater
is changed at a predetermined speed in the growth operation of the
silicon carbide ingot. Hereinafter, the example embodiments will be
described in more detail.
[0046] An object of example embodiments is to provide a
manufacturing method for a silicon carbide ingot, which can exhibit
a good quality and a system for manufacturing a silicon carbide
ingot, by preparing a guide unit for inducing a shape of a silicon
carbide ingot when grown during manufacturing processes of a
silicon carbide ingot.
[0047] Another object of example embodiments is to provide a
manufacturing method for a silicon carbide ingot, which can change
a temperature gradient inside a reactor depending on growing of an
ingot and a system for manufacturing a silicon carbide ingot, by
moving a heating mean in a predetermined speed, in an operation of
main growth of an ingot within manufacturing processes.
[0048] Another object of example embodiments is to provide a
manufacturing method for a silicon carbide ingot, which is improved
in a crystal quality and a silicon carbide ingot manufactured
according to the method, by having a diameter ratio of the front
and the rear of a silicon carbide ingot to be a certain value and
having a certain angle of inclination in edges linking the front
and the rear, through the above manufacturing method of a silicon
carbide ingot and the like.
[0049] Another object of example embodiments is to provide a method
and a system for manufacturing a silicon carbide ingot and a
silicon carbide wafer having a good crystal quality and reducing
defect occurrence.
[0050] A manufacturing method for a silicon carbide ingot, a system
(manufacturing device) for manufacturing a silicon carbide ingot
according to embodiments may improve a crystal quality of a
manufactured silicon carbide ingot, by adjusting relative positions
of a guide unit, which induces a growing shape of a silicon carbide
ingot in a growth operation of a silicon carbide ingot, a reactor,
and a heater at a predetermined speed.
[0051] According to embodiments, it is possible to secure a crystal
quality of a manufactured silicon carbide ingot and minimize defect
occurrence, by optimizing characteristics such as a volume ratio
between a reactor and a heat insulating means, a temperature
difference between an upper portion and a lower portion in a
reactor, a density of a heat insulating material, a resistivity of
a heat insulating material, and the like when a silicon carbide
ingot and a wafer are manufactured.
[0052] A silicon carbide ingot manufactured according to
embodiments has advantages that are lowering a defect density
numerical value and hardly showing a crack or a crystal
polymorphism, by having a certain angle in an edge linking the
front and the rear, and having a certain value in a diameter ratio
of the front and the rear.
[0053] Method of Manufacturing Silicon Carbide Ingot
[0054] In one general aspect, a method of manufacturing a silicon
carbide ingot comprises, a preparation operation of disposing a
silicon carbide raw material 300 and a seed crystal 110 in the
internal space of a reactor 200 and adjusting the internal space to
a vacuum atmosphere (Sa); a cooling operation of cooling the
temperature of the internal space to room temperature (S2). The
proceeding operation comprises a procedure in which the heater is
moved.
[0055] The internal space comprises a guide unit 120 disposed to
surround the circumference surface of the silicon carbide seed
crystal 110 with a predetermined interval,
[0056] The guide unit is extended toward a direction facing a
silicon carbide raw material from the silicon carbide seed crystal
110,
[0057] The guide unit has a guide angle of inclination which is
tilted to an external side of the silicon carbide seed crystal 110
by -4.degree. to 50.degree. when a virtual reference line
connecting one side of the silicon carbide seed crystal 110 and the
silicon carbide raw material in the shortest distance is designated
as 0.degree., and
[0058] The moving of the heater 600 may have a relative position
which becomes more distant at a rate of 0.1 mm/hr to 0.48 mm/hr
based on the seed crystal.
[0059] The heater 600 and the reactor 200 may be installed to have
a relative position changeable to an up-and-down direction. The
relative position may be changed through the mover, and it may be
changed when one or more of the heater 600 and the reactor are
moved. Changing the relative position through movement of a heater
600 may be advantageous, not through a reactor's movement, for
further stable growth of a silicon carbide ingot.
[0060] FIGS. 1, 3, 4, and 5, illustrate an example of a silicon
carbide ingot system and a reactor 200. Referring to FIGS. 1, 3, 4,
and 5, a method of manufacturing a silicon carbide ingot, in
accordance with one or more embodiments, will be described.
[0061] The preparation operation (Sa) is an operation of disposing
the raw material 300 and the silicon carbide seed crystals 110 to
face each other in a reactor having an internal space and adjusting
the internal space to have a vacuum atmosphere.
[0062] In the preparation operation (Sa), the pressure in the
internal space may be reduced to be 50 torr or less, 10 torr or
less, or 5 torr or less, as only examples, and the pressure may be
reduced to be 1 torr or more. During the preparation operation (Sa)
which includes such a vacuum atmosphere, it is possible to
manufacture an ingot with more reduced defects.
[0063] The silicon carbide seed crystal 110 in the preparation
operation (Sa) may be applied with an appropriate size according to
the size of a target ingot. The C plane (000-1 plane) of the
silicon carbide seed crystal 110 may be directed toward the raw
material 300.
[0064] The silicon carbide seed crystal 110 in the preparation
operation (Sa) may comprise 4 inches or more of 4H silicon carbide,
or 6 inches or more of 4H silicon carbide, as only examples.
[0065] When the silicon carbide seed crystal 110 has a form
attached to the seed crystal holder (not shown in drawings), the
silicon carbide seed crystal 110 may further comprise an adhesive
layer disposed on the rear region. When the silicon carbide seed
crystal 110 has a form that is not directly adhered to the seed
crystal holder, the silicon carbide seed crystal 110 may further
comprise a protective layer disposed on the rear region. In this
example, it is possible to induce growth of a silicon carbide ingot
with more reduced defects.
[0066] The silicon carbide raw material 300 in the preparation
operation (Sa) may be a raw material in the form of a powder having
a carbon source and a silicon source, and the raw material may
comprise silicon carbide powder.
[0067] The silicon carbide raw material 300 may comprise, as an
example, a silicon carbide powder necked from each other or a
silicon carbide powder in which the surface is carbonized. In this
example, it is possible to help more efficient growth of silicon
carbide by inducing more stable sublimation of silicon carbide
during the growth process and the like.
[0068] The reactor 200 in the preparation operation (Sa) may be
applied if it is a vessel suitable for growth reaction of a silicon
carbide ingot, and specifically a graphite crucible may be applied.
In an example, the reactor may comprise a body 210 comprising an
internal space and an opening, and a cover 220 corresponding to the
opening, thereby sealing the internal space. The cover 220 may
further comprise a seed crystal holder formed integrally or
separately from the cover 220, and the seed crystal holder may fix
the silicon carbide seed crystal 110 so that the silicon carbide
seed crystal 110 and the silicon carbide raw material 300 face each
other.
[0069] The reactor 200 in the preparation operation (Sa) may
comprise a guide unit 120 disposed in an internal space to surround
the circumference surface of the silicon carbide seed crystal 110
with a predetermined interval.
[0070] The guide unit 120 may be extended toward a direction facing
the silicon carbide seed crystal 110 to a silicon carbide raw
material 300. The guide unit may have a guide angle of inclination
which is tilted to an external side of the silicon carbide seed
crystal 110 by -4.degree. to 50.degree. when a virtual reference
line connecting one side of the silicon carbide seed crystal 110
and the silicon carbide raw material 300 in the shortest distance
is designated as 0.degree.. The guide angle of inclination may be
40.degree. or less, or 25.degree. or less. The guide angle of
inclination may be 0.1.degree. or more, or 4.degree. or more. The
guide angle of inclination is allowed to satisfy such a range, and
thereby a silicon carbide ingot with reduced defects and an
excellent crystal quality can be easily manufactured.
[0071] The guide unit 120 in the preparation operation (Sa) may
comprise an amorphous carbon in the surface of a substance
composing the surface and may comprise a graphite having a lower
density than the density of reactor. Accordingly, an unnecessary
reaction with a raw material can be inhibited when a silicon
carbide ingot is grown.
[0072] The guide unit 120 in the preparation operation (Sa) may
have a non-resistivity of 10 .mu..OMEGA.m to 50 .mu..OMEGA.m or
less. Since the guide unit 120 may have such a non-resistivity, the
shape of a manufactured silicon carbide ingot can be stably
induced.
[0073] The guide unit 120 in the preparation operation (Sa) may
have a truncated shape with opened upper and lower portions, and
may protrude from, or may be attached to, the upper surface of the
interior of the reactor 200, or may have a triangular shape that
protrudes from, or is attached to, the silicon carbide seed crystal
110 from the inner diameter surface of the reactor. However, the
shape is not limited thereto, and any shape that induces the
circumference diameter of a silicon carbide ingot to be gradually
increased when the silicon carbide ingot is grown to a
perpendicular direction which is a direction of a raw material 300,
can be applied.
[0074] The upper end of the guide unit 120 in the preparation
operation (Sa) may be separate from the circumference surface of
the silicon carbide seed crystal 110 with an interval of 5 mm to 20
mm. The upper end of the guide unit 120 may be a location which has
the shortest distance with the circumference surface of the silicon
carbide seed crystal. When an unnecessary single crystal is formed
on the guide during growing processes of a silicon carbide ingot,
interference added to the silicon carbide ingot can be minimized by
allowing the guide unit 120 to be separate from a silicon carbide
seed crystal with such a range.
[0075] The guide unit 120 in the preparation operation (Sa) may
have a height of 30 mm or more, or 50 mm or less, based on a
direction connecting one side of the silicon carbide seed crystal
110 and the silicon carbide raw material 300 in the shortest
distance.
[0076] The reactor 200 in the preparation operation (Sa) may
further comprise a heat insulating material 400 disposed in the
external surface thereof and surrounding the reactor 200, at this
time the heat insulating material may be in contact with the
reactor 200, or may have a predetermined interval. In the reaction
chamber 500, such as a quartz tube, the heat insulating material
surrounding the reactor may be positioned. The temperature of
internal space of the reactor 200 may be controlled by the heater
600 disposed in an external region of the heat insulating material
and the reaction chamber 500.
[0077] The heat insulating material 400 in the preparation
operation (Sa) may have an air porosity of, as examples, 72% to
95%, of 75% to 93%, or of 80% to 91%. When the heat insulating
material satisfying the above air porosity is applied, crack
generation of the grown silicon carbide ingot may be further
reduced.
[0078] The heat insulating material 400 in the preparation
operation (Sa) may have a compressive strength of 0.2 Mpa or more.
The heat insulating material 400 may have a compressive strength of
0.48 Mpa or more, or 0.8 MPa or more. Additionally, the heat
insulating material may have a compressive strength of 3 MPa or
less, or 2.5 MPa or less. When the heat insulating material has
such a compressive strength, it is excellent in thermal/mechanical
stability, and the probability of occurrence of ash may be lowered,
so that a silicon carbide ingot with better quality may be
manufactured.
[0079] The heat insulating material 400 in the preparation
operation (Sa) may comprise a carbon-based felt, may specifically
comprise a graphite felt, and may comprise a rayon-based graphite
felt, or a pitch-based graphite felt.
[0080] The reaction chamber 500 may comprise a vacuum exhauster 700
connected to an internal region of the reaction chamber 500 and
configured to adjust the degree of vacuum inside the reaction
chamber 500, a plumbing portion 810 connected to the interior of
the reaction chamber 500 and introducing gas into the inside of the
reaction chamber 500, and a mass flow controller 800 to control
inflow of gas. Accordingly, the flow rate of the inert gas in a
subsequent growth operation and a cooling operation may be
controlled.
[0081] In the proceeding operation (Sb, S1), inert gas is injected
into the internal space, and the raw material are sublimated by
adjusting the temperature, pressure and atmosphere of the internal
space, thereby inducing the growth of the silicon carbide ingot 100
from the silicon carbide seed crystal 110.
[0082] The proceeding operation (Sb, S1) may substantially change
the internal space to have an inert gas atmosphere. The inert gas
atmosphere may be formed by decompressing the internal space of the
reactor 200 which has atmospheric atmosphere, thereby substantially
inducing the atmosphere to a vacuum atmosphere, after the process
of disposing the silicon carbide raw material 300 and seed crystals
110, and then injecting an inert gas. But it is not necessarily
limited to this method.
[0083] The inert gas atmosphere in the proceeding operation (Sb,
S1) refers to that the atmosphere of the internal space in the
growth operation is not atmospheric atmosphere, and is based on an
inert gas atmosphere, but the inert gas atmosphere also comprises
an atmosphere in which a trace amount of gas is injected for the
purpose of doping a silicon carbide ingot. An inert gas is applied
to the inert gas atmosphere, and in an example, the inert gas may
be argon, helium or a mixture thereof, but is not limited
thereto.
[0084] The proceeding operation (Sb, S1) may proceed while heating
the reactor 200 or the internal space of the reactor 200 by the
heater 600, and simultaneously or individually with the heating,
may proceed while decompressing the internal space to adjust the
degree of vacuum and injecting an inert gas.
[0085] The proceeding operation (Sb, S1) comprises a process of
sublimating the silicon carbide raw material 300 and a process of
inducing a silicon carbide ingot 100 to grow on one surface of the
silicon carbide seed crystal 110.
[0086] The heater 600 may be disposed around the reactor 200, and
may be installed so as to be movable in the up-and-down direction
substantially parallel to an arbitrary line from the silicon
carbide seed crystal 110 to the raw material 300. The heater 600
may comprise a moving device or mover that changes a relative
position in the up-and-down direction between the heater 600 and
the reactor 200. Accordingly, the relative position between the
reactor 200 and the heater 600 may be changed, and a temperature
gradient in the internal space can be induced. In particular, the
heater 600 may make a temperature difference between an upper
portion of the internal space and a lower portion of the internal
space.
[0087] The heater 600 may be an induction heater formed in a spiral
coil along the outer peripheral surface of the reactor 200 or the
outer peripheral surface of the heat insulating material 400
surrounding the reactor 200, but is not limited thereto.
[0088] The proceeding operation (Sb, S1) sequentially may comprise
a pre-growth process (Sb) and a growth process (S1), wherein the
pre-growth process may sequentially comprise a first process, a
second process, and a third process, wherein the first process
(Sb1) is a process that changes the high-vacuum atmosphere in the
preparation operation to an inert atmosphere, the second process
(Sb2) is a process of raising the temperature of the internal space
using the heater 600, and the third process (Sb3) is a process of
depressurizing the pressure of the internal space to reach the
growth pressure with heating internal space to have the growth
temperature.
[0089] The growth process (S1) is a process that maintains the
internal space at the growth temperature and the growth pressure,
and induces the ingot to grow.
[0090] The first process (Sb1) may be performed by injecting an
inert gas such as argon. In this example, the pressure of the
internal space may be 500 torr to 800 torr.
[0091] The second process (Sb2) is to heat the lower portion 240 of
the internal space to have a starting temperature of 1500.degree.
C. to 1700.degree. C. before growth. The temperature increase in
the second process (Sb2) may proceed at a rate of 1.degree. C./min
to 10.degree. C./min.
[0092] In the third process (Sb3), the temperature may be increased
so that the temperature of the lower portion of the internal space
becomes the growth temperature 2100.degree. C. to 2500.degree. C.,
and the growth pressure may be reduced to 1 torr to 50 torr. The
temperature increase in the third process (Sb3) may proceed at a
rate of 1.degree. C./min to 5.degree. C./min.
[0093] The second process and the third process may prevent the
occurrence of polymorphism other than the target crystal in the
above range of temperature increase rate and pressure. And the
second process and the third process can induce stable growth of
the ingot.
[0094] Referring to FIG. 5, the upper portion 230 of the internal
space is a partial space of the internal space close to the surface
of the silicon carbide seed crystal 110 or the ingot, and the lower
portion of the internal space 240 is a space of the internal space
close to the surface of the raw material 300. Specifically, the
upper portion 230 of the internal space may be a position located
at a distance about 5 mm or more below the surface of the silicon
carbide seed crystal 110 or the ingot, and may be a position having
a height of 10 mm from the lowest end of the guide unit 120 to the
upper end thereof. The lower portion 240 of the internal space may
be a position located at a distance about 10 mm or more above the
raw material 300. If the measured temperature is different for each
measured position when the upper portion of the internal space and
the lower portion of the internal space is the same position seen
in a length direction of a crucible, the temperature measurement is
based on the temperature of the center.
[0095] In the growth process (S1), the relative position of the
heater 600 may be moved based on the reactor 200.
[0096] In the growth process (S1), the "maintaining the growth
pressure" may include an example where the pressure of the injected
gas is somewhat adjusted as needed within a range in which the
growth of the silicon carbide ingot does not stop under reduced
pressure. Additionally, the "maintaining the growth pressure" means
that the pressure in the internal space is maintained within a
predetermined range within a limit that maintains the growth of the
silicon carbide ingot.
[0097] In the pre-growth process (Sb), a predetermined temperature
difference may be generated between the temperature at the upper
portion 230 of the internal space and the temperature at the lower
portion of the internal space. The temperature difference at the
starting temperature before growth may be 40.degree. C. to
60.degree. C., or 50.degree. C. to 55.degree. C. The temperature
difference at the growth temperature may be 110.degree. C. to
160.degree. C., or 135.degree. C. to 150.degree. C. In view of this
temperature difference, the pre-growth process may minimize the
occurrence of polymorphism other than the target crystal, and can
induce stable growth of the ingot.
[0098] The heating rate of the third process (Sb) may be less than
the average heating rate of the total second process (Sb2) and
third process (Sb3). The average heating rate of the total second
process (Sb2) and third process (Sb3) is a value obtained by
dividing the difference between the temperature at the start of the
second process and the temperature at the end of the third process
by the time taken, and the heating rate of the third process refers
to the heating rate at each point in the third process.
[0099] The heater 600 may have a maximum heating region, and the
maximum heating region refers to a portion that has the highest
temperature in the atmosphere of the internal space heated by the
heater 600. When the heater 600 surrounds the side surface of the
reactor 200 in the form of a spiral coil, the internal space
corresponding to the center of the heater 600 is the maximum
heating region. In an example, when assuming a line (the vertical
center line) in the vertical direction connecting the center of the
seed crystal 110 and the silicon carbide raw material 300, and a
surface (the central surface of heater 600) extended in the
horizontal direction from the center of the height of the heater
600, the maximum heating region may be a region in which an
intersection point between the vertical center line and the
horizontal surface of the heater 600 is located.
[0100] The second process (Sb) and the third process (Sc) may be
performed by locating the maximum heating region of the heater 600
to become the lower portion of the reactor 200 and the surface of
the raw material 300, and when the heater 600 has a spiral coil
shape, a temperature difference between the upper portion of the
internal space and the lower portion of the internal space may be
generated by changing the number of winding and thickness of heater
600.
[0101] The growth process (S1) is a process of sublimating the raw
material to form a silicon carbide ingot, after the internal space
is heated to the growth temperature in the third process (Sb3). In
this example, the growth process may maintain the growth
temperature of the internal space to form a silicon carbide ingot.
Maintaining the growth temperature does not mean that it must be
performed at a fixed proceeding temperature during the growth
process, but means that a silicon carbide is grown in a temperature
range where the growth of the silicon carbide ingot practically
does not stop, even if there is a slight change in the absolute
temperature.
[0102] The relative position of the heater 600 with respect to the
reactor 200 in the growth process (S1) may become more distant at
rate of 0.1 mm/hr to 0.48 mm/hr based on the seed crystal 110.
Additionally, the relative position may become more distant at rate
of 0.1 mm/hr to 0.4 mm/hr, or at rate of 0.2 mm/hr to 0.3 mm/hr
based on the seed crystal 110. The speed range is quite low, and if
the relative position is changed at this speed, the growth process
can prevent the occurrence of polymorphic crystals other than the
target crystal and can grow a silicon carbide ingot with reduced
defects.
[0103] In the growth process (S1), the change of the relative
position of the heater 600 with respect to the reactor 200 and the
seed crystal 110 may be performed after reaching the growth
temperature, and may be performed after 1 hour to 10 hours after
reaching the growth temperature.
[0104] In the growth process (S1), the upper portion 230 of the
internal space may have a sub-heating region of which the
temperature is 110.degree. C. to 160.degree. C. lower than the
temperature of the maximum heating region in the reactor 200.
Additionally, the temperature of the sub-heating region may be
135.degree. C. to 150.degree. C. lower than the temperature of the
maximum heating region.
[0105] The sub-heating region refers to a region having a
relatively low temperature in the atmosphere of the internal space
heated by the heater 600. When the heater 600 surrounds the side
surface of the reactor 200 in the form of a spiral coil, the
sub-heating region may be located above the maximum heating
region.
[0106] When assuming a line in the vertical direction connecting
(the vertical center line) the center of the seed crystal 110 and
the silicon carbide raw material 300, and a surface (the central
surface of heater 600) extended in the horizontal direction from
the center of the height of the heater 600, the sub-heating region
may be located between the maximum heating region and the silicon
carbide seed crystal 110 or ingot surface. Also, preferably, at
least some of the sub-heating region may overlap the upper portion
of the internal space.
[0107] The heater 600 can be moved up-and-down direction based on
the reactor 200 through a moving device that changes a relative
position between the heater 600 and the reactor 200 to the
up-and-down direction. That is, it is possible to move the heater
600 in a substantially parallel direction based on an arbitrary
line from the seed crystal 110 disposed in the reactor 200 toward
the silicon carbide raw material 300.
[0108] The heater 600 in the growth process (S1) may be moved while
descending relative to the reactor 200 at the above speed.
[0109] In an example, the growth temperature in the growth process
(S1) may be 2100.degree. C. to 2500.degree. C., or 2200.degree. C.
to 2400.degree. C. based on the maximum heating region.
Additionally, the growth temperature in the growth process (S1) may
be 1900.degree. C. to 2300.degree. C. or 2100.degree. C. to
2250.degree. C. based on the upper portion 230 of the internal
space.
[0110] During the growth process (S1), the total moving distance of
the heater 600 may be 10 mm or more, or 15 mm or more.
Additionally, during the growth process (S1), the total moving
distance of the heater 600 may be 45 mm or less, or 30 mm or
less.
[0111] The growth process may proceed for 5 hours to 200 hours.
Additionally, the growth process may be proceeded for 75 hours to
100 hours.
[0112] The pre-growth process (Sb) and/or the growth process (S1)
may be performed while the reactor 200 rotates on the vertical
direction, and through this, a temperature gradient that is more
favorable for growth of a silicon carbide ingot may be induced to
be formed.
[0113] In the proceeding operation (Sb, S1), an inert gas of a
predetermined flow rate may be added to the exterior of the reactor
200. The inert gas may form a flow of gas in the internal space of
the reactor 200 and may induce a flow of gas from the raw material
300 toward the silicon carbide seed crystal 110. Accordingly, a
stable temperature gradient of the reactor 200 and the internal
space can be formed.
[0114] The cooling operation (S2) is an operation of cooling the
silicon carbide ingot grown through the proceeding operation under
conditions of a predetermined cooling rate and flow rate of an
inert gas.
[0115] In the cooling operation (S2), cooling may be proceeded at a
rate of 1.degree. C. to 10.degree. C. Also, cooling may proceed at
a rate of 1.degree. C. to 5.degree. C.
[0116] In the cooling operation (S2), pressure control of the
internal space of the reactor 200 may proceed simultaneously or
separately. The pressure may be controlled to have a pressure in
the internal space of 800 torr at maximum.
[0117] In the cooling operation (S2), like the proceeding
operation, an inert gas of a predetermined flow rate may be added
to the inside of the reactor 200. The inert gas may form a flow of
gas in the internal space of the reactor 200. Additionally, the
inert gas may form a flow of gas from the raw material 300 toward
the silicon carbide seed crystal 110.
[0118] The cooling operation may comprise a first cooling process
and a second cooling process. The first cooling process is a
process of pressurizing the pressure of the internal space of the
reactor 200 to be at least atmospheric pressure, and cooling the
temperature of the internal space to be 1500.degree. C. to
1700.degree. C. based on the upper portion 230 of the internal
space, and the second cooling process is a process of cooling the
temperature of the internal space to room temperature after the
first cooling operation.
[0119] The recovery in the cooling operation may be achieved by
cutting the rear of the silicon carbide ingot in contact with the
seed crystal 110. The silicon carbide ingot cut in this way shows a
favorable height difference between the center of the grown end and
the edge, and can have a reduced defect density. The specific shape
and defect density of the silicon carbide ingot will be described
below.
[0120] Silicon Carbide Wafer Manufacturing Method
[0121] In one general aspect, a silicon carbide wafer manufacturing
method, in accordance with one or more embodiments, may comprise a
cutting operation of cutting a silicon carbide ingot manufactured
according to the above to prepare a silicon carbide wafer; and may
polish the edge of the silicon carbide ingot before the cutting
operation and thereby the silicon carbide ingot may have a cylinder
shape processed to have regular diameter.
[0122] The cutting operation may cut the silicon carbide ingot at
regular thickness intervals, and a predetermined off angle from the
(0001) surface of the silicon carbide ingot or a surface where
growth is started. The off angle may be 0.degree. to
10.degree..
[0123] The cutting operation may cut the silicon carbide wafer to
have a thickness of 150 .mu.m to 900 .mu.m, or 200 .mu.m to 600
.mu.m, but is limited thereto.
[0124] The silicon carbide wafer manufacturing method may comprise
a processing operation of flattening the thickness of a silicon
carbide wafer prepared through the cutting operation and polishing
the surface thereof.
[0125] The processing operation may apply wheel grinding and the
like to both surfaces of a silicon carbide wafer, and in this time
the polishing material used in wheel grinding may be a diamond
polishing material. Through the process of flattening the thickness
in the processing operation, damage and stress added to a wafer in
the cutting operation can be reduced and the thickness can be
flattened.
[0126] The process of polishing the surface of the processing
operation may further comprise a wet or dry etching operation.
[0127] The processing operation may further comprise a chemical
mechanical polishing operation. The chemical mechanical polishing
may be performed by adding polishing particle slurry to a polishing
pad placed on a plane and contacting a silicon carbide wafer to the
polishing pad in a predetermined pressure with rotating the
polishing pad and the silicon carbide wafer.
[0128] The silicon carbide wafer manufactured through the
manufacturing method has excellent advantages of a reduced defect
density, a bending characteristic, and a bow absolute value of 50
.mu.m or less.
[0129] Silicon Carbide Ingot Manufacturing Method
[0130] In a general aspect, a silicon carbide ingot manufacturing
method, in accordance with one or more embodiments, includes a
preparation operation of disposing a raw material 300 and a silicon
carbide seed crystal 110 to be separate in a reactor 200 having an
internal space; a growth operation of sublimating the raw material
by adjusting the temperature, the pressure, and the atmosphere of
the internal space and preparing a silicon carbide ingot 100 grown
from the silicon carbide seed crystal 110; a cooling operation of
cooling the reactor 200 and retrieving the silicon carbide ingot; a
heat insulating material 400 surrounding the external surface of
the reactor 200, and a heating unit 600 for adjusting the
temperature of the internal space.
[0131] The heat insulating material may comprise a heat insulating
material circumference part 410 surrounding the external surface of
the reactor 200.
[0132] The volume of the reactor Vc and the volume of the heat
insulating material circumference part Vi may have a ratio Vc/Vi of
0.05 to 0.8.
[0133] The growth operation may include a heating process that
increases the temperature of the internal space from room
temperature to a first temperature, a first growing process that
heats the internal space from a first temperature to a second
temperature, and a second growing process that maintains the second
temperature, to prepare a silicon carbide ingot.
[0134] The first temperature may be a temperature to start
depressurizing of the internal space.
[0135] The second temperature may be a temperature that induces
growth of a silicon carbide ingot at the depressurized pressure
after the depressurization of the internal space is completed.
[0136] A temperature difference may be a difference between an
upper temperature and a lower temperature in the internal
space.
[0137] The temperature difference in the second temperature may be
160.degree. C. to 240.degree. C.
[0138] The preparation operation may dispose a raw material and a
silicon carbide seed crystal 110 to be separated and face each
other in a reactor 200 having an internal space.
[0139] The silicon carbide seed crystal 110 may be a proper size
depending on a desired wafer, and the C surface ((000-1) surface)
of the silicon carbide seed crystal 110 may face the direction of a
raw material 300.
[0140] The silicon carbide seed crystal 110 may comprise a 4H
silicon carbide in four inches or more, in six inches or more, or
in eight inches or more. The silicon carbide seed crystal 110 may
be twelve inches or less.
[0141] The raw material 300 may be a powder shape having a carbon
source and a silicon source, and raw material in which the powder
is necking treated or a silicon carbide powder whose surface is
carbonated may be applied.
[0142] In an example, the reactor 200 may be any container that
grows a reaction of a silicon carbide ingot, and specifically a
graphite crucible may be applied.
[0143] Referring to FIG. 4, in an example, the reactor 200 may
comprise a body 210 comprising an internal space an opening, and a
cover 220 corresponding to the opening. The enclosure of the body
210 and the cover 220 may form the internal space. The crucible
cover 220 may further comprise a seed crystal holder as one body or
a separate body with the crucible cover 220, may fix a silicon
carbide seed crystal 110 through the seed crystal holder, and
thereby may allow a silicon carbide seed crystal 110 and a raw
material to face each other.
[0144] The reactor 200 may be fixed by being surrounded by a heat
insulating material 400, and the heat insulating material 400
surrounding the reactor 200 may be located inside a reacting
chamber 500 such as a quartz tube. A heater 600 may be equipped in
the external of the heat insulating material 400 and the reacting
chamber 500 to control the temperature of the internal space of the
reactor 200.
[0145] The heat insulating material 400 may have a non-resistivity
of 8.times.10.sup.-3 .OMEGA.m or less, 5.times.10.sup.-3 .OMEGA.m
or less, or 3.1.times.10.sup.-3 .OMEGA.m. The heat insulating
material 400 may have a non-resistivity of 1.times.10.sup.-4
.OMEGA.m or more, 2.5.times.10.sup.-4 .OMEGA.m or more, or
1.0.times.10.sup.-4 .OMEGA.m or more. When a heat insulating
material 400 having such a non-resistivity is applied, defect
occurrence of a growing silicon carbide ingot may be more
reduced.
[0146] Referring to FIG. 9, the heat insulating material 400 may
comprise a heat insulating material circumference part 410
surrounding the side of the reactor 200, and the thickness of the
heat insulating material circumference part may be 200 mm to 600
mm, or 300 mm to 500 mm, as only examples. When a heat insulating
material 400 having such a thickness of the circumference part is
applied, a silicon carbide ingot in a high quality may be
grown.
[0147] The heat insulating material 400 may have a porosity of 72%
to 95%, 75% to 93%, or 80% to 91%. When a heat insulating material
400 satisfies the above porosity, defect occurrence of a growing
silicon carbide ingot may be further reduced.
[0148] The heat insulating material 400 may comprise a carbon-based
felt, and specifically, may comprise a graphite felt, and even more
specifically, may comprise rayon-based graphite felt, or a
pith-based graphite felt.
[0149] The density of the heat insulating material 400 may be 0.14
g/cc to 0.28 g/cc, or 0.15 g/cc to 0.17 g/cc. When a heat
insulating material having such a density is applied, a silicon
carbide ingot in a high quality can be grown.
[0150] The ratio Vc/Vi of a volume of the reactor 200 Vc and the
volume of a heat insulating material circumference part 410 Vi may
be 0.05 to 0.8, 0.1 to 0.7, or 0.3 to 0.5, as only examples.
[0151] Referring to FIG. 7, the volume of the reactor Vc may be a
volume of a reactor 200 itself except for the internal space. The
heat insulating material circumference part 410 may surround the
side except for upper and lower covers of the reactor 200 as
illustrated in FIGS. 9 to 11, or may surround the internal space.
Similar to FIG. 4, in FIGS. 9-11 a seed crystal 110 may be disposed
in an upper portion of the internal space, and a raw material 300
may be disposed in a lower portion 240 of the internal space.
[0152] The volume of the reactor 200 Vc and the volume of the heat
insulating material circumference part 410 Vi may be actually
measured or may be calculated by a three-dimension modeling program
(ex. CATIA, SolidWorks, and AutoCAD).
[0153] The heat insulating material circumference part 410 may be a
hollow type having an inner and an outer diameter. The outer
diameter of the heat insulating material circumference part 410 may
be eight inches or more, or fourteen inches or less, as only
examples.
[0154] The heat insulating material 400 may further comprise a heat
insulating material upper lead which is disposed in an upper
portion of the reactor 200, and a heat insulating material lower
lead, which is disposed in a lower portion of the reactor 200. The
heat insulating material upper lead and the heat insulating
material lower lead may respectively cover upper and lower portions
of the heat insulating material circumference part 410 to be closed
and may treat the internal of the heat insulating material to be
heat insulated.
[0155] Since the reactor 200 and the heat insulating material
circumference part 410 may have a suitable volume ratio, defect
occurrence of a growing silicon carbide ingot may be minimized, and
the occurrence of a micropipe or the like may be minimized when a
wafer is manufactured through a silicon carbide ingot. When being
out from such a Vc/Vi ratio, a growing silicon carbide ingot may
have an excessive curvature, and accordingly the quality may be
degraded due to the increase of residual stress with increasing the
possibility of crack occurrence.
[0156] The reacting chamber 500 may comprise a vacuum degassing
device 700 connected to the internal of the reacting chamber, and
that adjusts vacuum degree inside the reactor 200, a pipe 810
connected to the internal of the reacting chamber that induces gas
to flow into the interior of the reacting chamber, and a mass flow
controller 800, that controls flow of gas. By implementing these
elements, quantity of flow of inert gas may be adjusted in
subsequent growth operations and cooling operations.
[0157] The growth operation may be performed by heating the reactor
200 and the internal space of the reactor 200 by the heater 600,
may depressurize the internal space at the same time with the
heating operation or as a separate process to adjust the vacuum
degree, and may induce growth of a silicon carbide ingot by
injecting internal gas.
[0158] The heater 600 may be equipped to be movable in an
up-and-down direction of the reactor 200, accordingly relative
positions of the reactor 200 and the heater 600 may be changed
based on this movement, and an upper portion of the internal space
230 and a lower portion of the internal space 240 may have a
temperature difference based on the heater 600. Specifically, the
heater 600 may add a temperature difference to a silicon carbide
seed crystal 110 of an upper portion and a raw material 300 of a
lower portion in the internal space.
[0159] In an example, the heater 600 may be formed as a spiral coil
along to a circumference surface of the reactor 200 or a heating
material 400 surrounding a reactor 200.
[0160] Referring to FIG. 2, the growth operation may comprise a
heating process (Sb1 or Sb2) that increases the temperature of the
internal space from room temperature to a first temperature; a
first growing process (Sb3) that heats the internal space from a
first temperature to a second temperature; and a second growing
process (S1) that maintains the second temperature, and thereby may
prepare a silicon carbide ingot.
[0161] Before the growth operation, a depressurizing process (Sa)
that depressurizing the internal space in a state of the atmosphere
may be implemented.
[0162] The heating to the first temperature may proceed at a rate
of 3.degree. C./min to 13.degree. C./min, or 5.degree. C./min to
11.degree. C./min. The heating to the starting temperature for
pre-growth may proceed at a rate of 7.degree. C./min to 10.degree.
C./min.
[0163] The depressurizing process Sa may be performed to have a
pressure of the internal space of 10 torr or less, or 5 torr or
less, as examples.
[0164] The heating process (Sb1 or Sb2) may be performed to have a
pressure of the internal space of 500 torr to 800 torr by injecting
an inert gas such as argon or nitrogen, and the heating may be made
to a lower portion of the internal space to have a temperature of
1500.degree. C. to 1700.degree. C. at a rate of 1.degree. C./min to
10.degree. C./min.
[0165] Referring to FIG. 5, an upper portion of the internal space
230 in the growth operation may be a position corresponding to a
surface of a silicon carbide seed crystal 110, and a lower portion
of the internal space 2410 may be a position corresponding to a
surface of a raw material 300.
[0166] The first temperature refers to a temperature when
sublimating of the raw material 300 is partially started, and may
be a temperature after the heating process (Sb1 or Sb2) before the
growth operation as indicated in a dotted line region of FIG. 2, or
may be a temperature implemented when depressurizing of the
internal space is started after injection of an inert gas in the
heating process. Specifically, it may be 1500.degree. C. to
1700.degree. C., or 1600.degree. C. to 1640.degree. C. based on a
lower portion of the internal space 240.
[0167] The first temperature may be 1450.degree. C. to 1650.degree.
C. or 1550.degree. C. to 1587.degree. C. based on an upper portion
of the internal space 230.
[0168] The first growing process (Sb3) may have a temperature
difference between an upper portion of the internal space 230 and a
lower portion of the internal space 240 of 40.degree. C. to
60.degree. C., or 50.degree. C. to 55.degree. C. at the first
temperature.
[0169] The second temperature refers to a temperature when
sublimating of the raw material 300 is started in earnest, and may
be a temperature after heating of the first growing process is made
as indicated in a dotted line region of FIG. 2, or may be a
temperature that induces the growth of a silicon carbide ingot
under the depressurized pressure after depressurizing of the
internal space is completed. Additionally, the pressure may be
changed within .+-.10% compared to the depressurized pressure to
induce the growth of a silicon carbide ingot at the second
temperature.
[0170] The second temperature may be 2100.degree. C. to
2500.degree. C., or 2200.degree. C. to 2400.degree. C. based on a
lower portion of the internal space 240.
[0171] The second temperature may be 1900.degree. C. to
2300.degree. C., or 2100.degree. C. to 2250.degree. C. based on an
upper portion of the internal space 230.
[0172] The first growing process (Sb3) may have a temperature
difference between an upper portion of the internal space 230 and a
lower portion of the internal space 240 of 160.degree. C. to
240.degree. C., or 180.degree. C. to 220.degree. C. at the second
temperature. The temperature difference may be 196.degree. C. to
207.degree. C., or 202.degree. C. to 207.degree. C.
[0173] The first growing operation (Sb3) may increase a temperature
difference between an upper portion of the internal space 230 and a
lower portion of the internal space 240 together depending on the
temperature increase of the internal space.
[0174] The first growing process (Sb3) has a temperature range, a
temperature difference, and a temperature difference variation of
an upper portion of the internal space 230 and a lower portion of
the internal space 240, and thereby may minimize the occurrence of
polymorphism except a desired crystal when an initial silicon
carbide ingot is formed with enabling stable ingot growth. If the
first temperature and the second temperature of the first growing
process have a temperature difference which is less than the above
range, the possibility of forming a polycrystal is increased due to
being mixed of other crystals except a desired crystal, with
generating a possibility of lowering growth speed, and if the
temperature difference is more than the above range, the crystal
quality may be degraded.
[0175] The first growing process (Sb3) may perform depressurizing
from 1 torr to 50 torr with heating from the first temperature to
the second temperature.
[0176] The heating speed of the first growing process (Sb3) may be
smaller than the heating speed of the heating process (Sb1 or Sb2),
and may be smaller than the average heating speed of all the
heating process and the first growing process.
[0177] The heating speed of the first growing process (Sb3) may be
1.degree. C./min to 5.degree. C./min, or 3.degree. C./min to
5.degree. C./min. The above temperature range may prevent the
occurrence of polymorphism except a desired crystal and induce
stable growth.
[0178] The first growing process (Sb3) may be performed to have a
lower portion of the internal space 240 and the surface 240 of the
raw material as the maximum heating region of the heater 600, and
when the heater 600 is a spiral coil shape, it may add a desired
temperature difference between an upper portion of the internal
space 230 and a lower portion of the internal space 240 by changing
a number of winding or a thickness.
[0179] The second growing process (S1) maintains a second
temperature after heating to the second temperature in the first
growing process (Sb3), and thereby sublimates a raw material 300 in
earnest to prepare a silicon carbide ingot.
[0180] The second growing process (S1) may proceed for 5 hours to
180 hours, 30 hours to 160 hours, or 50 hours to 150 hours, but is
not limited thereto.
[0181] The growth process may be performed by being rotated on an
axis of an up-and-down direction of the reactor 200, and may
maintain a temperature gradient to be the same.
[0182] The growth operation may add an inert gas in a predetermined
quantity of flow to the exterior of the reactor 200. The inert gas
may flow in the internal space of the reactor 200, and the flow may
be made from the raw material 300 to the silicon carbide seed
crystal 110. Accordingly, a stable temperature gradient of the
reactor 200 and the internal space may be formed.
[0183] The inert gas of the second growing operation (S1) may be as
examples, argon, helium, or a mixture thereof.
[0184] After the second growing operation (S1), a cooling operation
(S2) of cooling the reactor 200, and a retrieving operation of
retrieving the silicon carbide ingot may be performed.
[0185] The cooling operation (S2) cools the silicon carbide ingot
gown through the growth operation under the condition of a
predetermined cooling speed and a predetermined quantity of flow of
an inert gas.
[0186] The cooling operation (S2) may perform cooling at a rate of
1.degree. C./min to 10.degree. C./min, or 3.degree. C./min to
9.degree. C./min, but is not limited thereto. The cooling operation
may perform cooling at a rate of 5.degree. C./min to 8.degree.
C./min, but is not limited thereto.
[0187] The cooling operation (S2) may perform pressure adjustment
of the internal space of the reactor 200 at the same time, or
alternately, the pressure adjustment may be performed as a separate
process from the cooling operation. The pressure adjustment may be
made to the internal space to have a pressure of 800 torr as the
maximum.
[0188] The cooling operation (S2) may add a predetermined quantity
of flow of an inert gas to the interior of the reactor 200 as the
same as the growth operation. The inert gas may be for example,
argon or nitrogen. The inert gas may flow in the internal space of
the reactor 200, and the flow may be made from the raw material 300
to the silicon carbide seed crystal 110.
[0189] The cooling operation (S2) may comprise a first cooling
process of pressurizing the internal space of the reactor 200 to
have a pressure equal to or greater than atmospheric pressure, and
cooling the internal space to have a temperature of 1500.degree. C.
to 1700.degree. C. based on an upper portion 230, and a second
cooling process of cooling the internal space to have room
temperature after the first cooling operation.
[0190] The cooling operation (S2) may perform an operation of
retrieving the silicon carbide ingot 100 by cutting the rear of a
silicon carbide ingot 100 in contact with the silicon carbide seed
crystal 110. A silicon carbide ingot 100 cut in this manner may
minimize loss of the rear region in contact with a seed crystal,
and show an improved crystal quality.
[0191] First Silicon Carbide Ingot Manufacturing System I
[0192] In a general aspect, a silicon carbide ingot manufacturing
system (manufacturing device), comprises a reactor 200 which has an
internal space; a heat insulating material 400 disposed on the
external surface of the reactor 200 and surrounding the reactor
200; and a heater 600 that adjusts the temperature of the reactor
200 or the internal space.
[0193] A silicon carbide seed crystal 110 may be located at an
upper portion of the internal space.
[0194] A raw material 300 may be located at a lower portion of the
internal space.
[0195] A moving device or mover that changes relative positions of
the heater 600 and the reactor 200 in an up-and-down direction may
be provided.
[0196] The internal space comprises a guide 120 equipped in the
external of the silicon carbide seed crystal 110.
[0197] The guide may extend in a perpendicular direction from the
silicon carbide seed crystal 110 to a silicon carbide raw material,
but may have an inner diameter surface tilted to the external side
by 50.degree. or less based on the perpendicular direction.
[0198] A silicon carbide ingot may be grown from the seed crystal,
and
[0199] The moving of the heater 600 may have a relative position
that becomes more distant at a rate of 0.1 mm/hr to 0.48 mm/hr
based on the seed crystal.
[0200] Referring to FIGS. 3 and 4, the reactor 200 may comprise a
body 210 comprising an internal space and an opening, and a cover
220 corresponding to the opening and sealing the internal space.
Other descriptions are the same as disclosed above.
[0201] The detailed elements of the guide unit 120 are the same as
described above.
[0202] The material and physical properties of the insulating
material 400 are the same as described above.
[0203] Referring to FIG. 4, the silicon carbide ingot manufacturing
system may comprise a reaction chamber 500 in which a reactor 200
surrounded by the insulating material 400 is placed therein. In
this example, the heater 600 may be provided outside the reaction
chamber 500 to control the temperature of the internal space of the
reactor 200.
[0204] The reaction chamber 500 may comprise a vacuum exhauster
700, a pipe 810 and a mass flow controller 800. The vacuum
exhauster 700 is a device connected to the interior of the reaction
chamber 500, and controls the degree of vacuum inside the reaction
chamber 500. The pipe 810 is a device connected to the interior of
the reaction chamber 500, and introduces gas into the reaction
chamber 500. The mass flow controller 800 is a device that controls
the gas inflow. By utilizing these elements, it is possible to
control the flow rate of the inert gas in the growth operation and
the cooling operation.
[0205] Referring to FIGS. 1 and 5, the relative position of the
heater 600 with respect to the reactor 200 may become more distant
at a rate of 0.1 mm/hr to 0.48 mm/hr, may be distant at a rate of
0.1 mm/hr to 0.4 mm/hr, or may be distant at rate of 0.2 mm/hr to
0.3 mm/hr based on the seed crystal. By satisfying the above moving
speed, a stable temperature difference and temperature gradient may
be applied, even if an ingot grows and the position of the surface
changes, and formation of polymorphic crystals other than the
target crystal is prevented.
[0206] The movement of the heater 600 may proceed in the proceeding
operation of sublimating the raw material by controlling the
temperature, pressure and atmosphere of the internal space, and
preparing a silicon carbide ingot grown from the seed crystal. In
an example, the movement of the heater 600 may proceed in the
second process and the third process, specifically the pre-growth
process of the proceeding operation, and the growth process. These
operations and processes are the same as described above.
[0207] The systems may comprise a moving device or mover that
changes the relative position of the heater 600 based on the
reactor 200 to an up-and-down direction, and in the growth
operation, the heater 600 may descend and move at the above speed
as shown in FIGS. 1 and 5.
[0208] The heater 600 may allow the maximum heating region to be
located at a lower portion of the internal space. The maximum
heating region is a region of the internal space at a position
corresponding to the center of the heater 600. When the heater 600
has a spiral coil shape, the internal region of the heater 600
having a predetermined length toward both ends from the center of
the heater 600, based on an arbitrary line connecting the silicon
carbide raw material and the seed crystal 110 may be the maximum
heating region. The temperature of the maximum heating region may
be 2100.degree. C. to 2500.degree. C., or 2200.degree. C. to
2400.degree. C.
[0209] The heater 600 may be moved so that the temperature of the
upper portion of the internal space is 110.degree. C. to
160.degree. C. lower than, or 135.degree. C. to 150.degree. C.
lower than the temperature of the maximum heating region in the
growth process. When the heater 600 has a spiral coil shape, the
upper portion of the internal space may be located above the center
which is the maximum heating region. The temperature of the upper
portion of the internal space may be 1900.degree. C. to
2300.degree. C., or 2100.degree. C. to 2250.degree. C.
[0210] The silicon carbide ingot manufacturing system may
sequentially proceed in the preparation operation (Sa), the
proceeding operation (Sb, S1), and the cooling operation (S2)
described above.
[0211] Second Silicon Carbide Ingot Manufacturing System
[0212] A silicon carbide ingot manufacturing system (manufacturing
device), in accordance with one or more embodiments, may comprise,
a reactor 200 having an internal space; a heat insulating material
400 surrounding the external surface of the reactor 200; a heater
600, that adjusts the temperature of the internal space to
manufacture a silicon carbide ingot,
[0213] The internal space may comprise a silicon carbide seed
crystal 110 at an upper portion 230.
[0214] The internal space may comprise a raw material at a lower
portion 240.
[0215] The heater may be equipped to be movable in an up-and-down
direction of the reactor 200 to adjust a temperature difference
between an upper portion of the internal space and a lower portion
of the internal space.
[0216] The volume of the reactor Vc and the volume of the heat
insulating material circumference part 410 Vi may have a ratio
Vc/Vi of 0.05 to 0.8.
[0217] The depressurizing operation (Sa), the heating operation
(Sb1 or Sb2), the first growing operation (Sb3), the second growing
operation (S1) and the cooling operation (S2) of the manufacturing
method for a silicon carbide ingot described above may be applied
through the silicon carbide ingot manufacturing system.
[0218] The silicon carbide seed crystal 110, the raw material 300,
the reactor 200, the heat insulating material 400, the heater 600,
of the silicon carbide ingot manufacturing system may be the same
as described in the First Silicon Carbide Ingot Manufacturing
Method.
[0219] Silicon Carbide Wafer Manufacturing Method
[0220] In a general aspect, a silicon carbide wafer manufacturing
method, in accordance with one or more embodiments, comprises, a
cutting operation of cutting a silicon carbide ingot manufactured
through the manufacturing method of a silicon carbide ingot to
prepare a silicon carbide wafer.
[0221] The cutting operation may cut the silicon carbide wafer to
have a thickness of 150 .mu.m to 900 .mu.m, or 200 .mu.m to 600
.mu.m, but is not be limited thereto.
[0222] After the cutting operation, the silicon carbide wafer
manufacturing method may further comprise a processing operation of
flattening the thickness of a prepared silicon carbide wafer, and
polishing the surface thereof.
[0223] In the processing operation a grind wheel may be a shape
having particles embedded in the surface, and the particles
embedded in the surface of the grinding wheel may be diamond.
[0224] The processing operation may be performed while the grinding
wheel and a wafer rotate in opposite directions from each
other.
[0225] The processing operation may have a grinding wheel whose
diameter is larger than the diameter of the wafer, and the diameter
of grinding wheel may be 250 mm or less, as only examples.
[0226] After the processing operation, the silicon carbide wafer
manufacturing method may further comprise an operation of
performing dry etching to the silicon carbide wafer.
[0227] The processing operation may further comprise a chemical
mechanical polishing operation.
[0228] The chemical mechanical polishing operation may be
implemented by contacting a fixed wafer to a rotating polishing
head in a predetermined pressure while adding polishing particle
slurry on a rotating plane.
[0229] After the processing operation, a washing operation
implemented through a general RCA (Radio Corporation of America)
chemical washing solution, as an example, may be further made.
[0230] A wafer manufactured through the manufacturing method has
advantages of a low defect density, a reduced number of impurity
particles, and a good surface characteristic, and when applying
this to the manufacture of elements, it is possible to manufacture
an element excellent in electrical and optical properties.
[0231] Silicon Carbide Wafer Manufacturing System
[0232] In a general aspect, a system (manufacturing device) for
silicon carbide wafer manufacturing system (manufacturing device),
in accordance with one or more embodiments, may comprise a silicon
carbide ingot manufacturing system, and a cutting device that cuts
a manufactured silicon carbide ingot to prepare a silicon carbide
wafer.
[0233] The cutting device may be a device which cuts a silicon
carbide ingot into a silicon carbide wafer shape which has a
regular thickness. In an example, a wire saw comprising diamond
particles may be implemented as the cutting device.
[0234] The cutting device may perform a cutting operation to have a
predetermined off angle with (0001) surface of the silicon carbide
ingot, and the off angle may be 0.degree. to 10.degree..
[0235] The silicon carbide wafer manufacturing system may further
comprise a grinding device that polishes the thickness of a cut
silicon carbide wafer and polishing the surface, an etching device
that performs dry or wet etching to the surface of a silicon
carbide wafer, a chemical mechanical polishing device, and the
like.
[0236] A silicon carbide wafer manufactured through the system for
manufacturing the has excellent advantages of a reduced defect
density, a bending characteristic, a bow absolute value of 50 .mu.m
or less.
[0237] Silicon Carbide Wafer 10
[0238] In a general aspect, a silicon carbide wafer 10 in
accordance with one or more embodiments, may include a micropipe
density of 1/cm.sup.2 or less, and a full width at half maximum of
0.01.degree. to 0.5.degree. according to High Resolution X-ray
Diffraction (HRXRD) analysis.
[0239] The silicon carbide wafer 10 may have a full width at half
maximum of the rocking curve of 0.01.degree. to 0.5.degree.,
0.02.degree. to 0.4.degree., or 0.1.degree. to 0.4.degree.. A
silicon carbide wafer having such a characteristic may have an
excellent crystalline structure characteristic and may improve the
characteristic of an element manufactured through subsequent
processes.
[0240] The rocking curve was measured by applying High Resolution
X-ray Diffraction system (HR-XRD system) as follows: fitting
[11-20] direction of the silicon carbide wafer to an X-ray route,
setting an angle of an X-ray source and an X-ray detector to be
2.theta. (35.degree. to 36.degree.), and after that adjusting an
omega (.omega. or .theta. of an X-ray detector) angle to be fitted
to an off angle of a silicon carbide wafer to measure a rocking
curve. The crystallinity may be evaluated through a full width at
half maximum value of the rocking curve. Specifically, among
silicon carbide wafers applied with an off angle which is an angle
selected from a range of 0.degree. to 10.degree. with respect to
(0001) surface of a silicon carbide ingot, when an off angle is
0.degree., the omega angle is 17.8111.degree., when an off angle is
4.degree., the omega angle is 13.811.degree., and when an off angle
is 8.degree., the omega angle is 9.8111.degree..
[0241] The silicon carbide wafer 10 may be four inches or more,
five inches or more, six inches or more, or eight inches or more.
The diameter of the wafer may be twelve inches or less, or ten
inches or less.
[0242] The silicon carbide wafer 10 may comprise a 4H silicon
carbide.
[0243] The silicon carbide wafer 10 may be a wafer before the
formation of an epitaxial layer in the surface. In an example, the
silicon carbide wafer may be a wafer after being cut from a silicon
carbide ingot before passing through flattening processing and a
chemical mechanical polishing process.
[0244] The silicon carbide wafer 10 may comprise Si plane as one
side 11 where a silicon atom layer is shown on the surface and C
plane as the other side 12 where a carbon atom layer is shown on
the surface like an illustration of FIG. 13. When a silicon carbide
wafer is manufactured by a cutting process from a silicon carbide
ingot, it may be easily cut in an interface of a carbon atom layer
and a silicon atom layer haven by a silicon carbon single crystal
or in a direction parallel to the interface. Accordingly, a surface
where carbon atoms are mainly exposed and a surface where silicon
atoms are mainly exposed are shown on the cut surface.
[0245] Si plane as one side 11 of the silicon carbide wafer 10 may
have an Ra roughness of 0.3 nm or less, or 0.2 nm or less. The one
side may have an Ra roughness of 0.01 nm or more. A wafer having
such a roughness range may improve electrical properties when an
element is manufactured through subsequent processes.
[0246] The silicon carbide wafer may have a thickness of 100 .mu.m
to 900 .mu.m, the thickness is not limited thereto and any
thickness suitable to a semiconductor element can be applied.
[0247] Silicon Carbide Ingot 100
[0248] In a general aspect, a silicon carbide ingot 100, in
accordance with one or more embodiments, is a silicon carbide ingot
comprising, a front 102 and a rear 101 which is an opposite side
thereof, wherein the rear may be cut from a silicon carbide seed
crystal 110, the maximum height perpendicular to the rear may be 15
mm or more, the diameter of the rear Db and the circumference
diameter of the front may have a ratio Df/Db of 0.95 to 1.17, and a
line perpendicular to the rear from one side of the circumference
of the rear, and an edge line linking one side of the front close
to the one side of the circumference of the rear from a plane
comprising the line perpendicular to the rear from one side of the
circumference of the rear and a diameter of the rear may have an
angle of -4.degree. to 50.degree..
[0249] Referring to FIG. 6, the silicon carbide ingot 100 may be
manufactured through the manufacturing method of the silicon
carbide ingot, and may be controlled to have a predetermined shape
through a guide 120, a heater 600 (which is movable, and the moving
speed thereof can be adjusted), a temperature difference, and the
like equipped during manufacturing processes.
[0250] The rear region 101 of the silicon carbide ingot 100 may
have a section that is substantially similar to a section of the
silicon carbide seed crystal 110, the section may have a circular
shape, and may have a diameter Db.
[0251] The front region of the silicon carbide ingot 102 may have a
convex surface, or a plane, and may have a circumference of the
edge and a diameter of the circumference Df.
[0252] The front of the silicon carbide ingot 120 may have a
diameter of 178 mm or less, 170 mm or less, or 158 mm or less. A
silicon carbide ingot having such a Df value can have an excellent
crystal quality. The Df value range may be based on a silicon
carbide seed crystal 110 having a diameter of 150 mm.
[0253] The silicon carbide ingot may have a ratio Df/Db of a
diameter of the rear 101 Db and a diameter of the circumference of
the front 102 Df of 0.95 to 1.17, or 1 to 1.1. Additionally, in
this time the silicon carbide ingot 100 may have a maximum height
of 15 mm or more, 18 mm or more, or 21. 6 mm or more in a direction
perpendicular to the rear 101. A silicon carbide ingot having such
a diameter ratio and a height may be one whose internal stress
occurrence is minimized and may show a good crystal quality.
[0254] Referring to FIG. 6, a line perpendicular to the rear region
101 from one side of the circumference of the rear region 101 and
an edge line linking one side of the front region 102 close to the
one side of the circumference of the rear region 101 from a plane
comprising the line perpendicular to the rear from one side of the
circumference of the rear and a diameter of the rear may have an
angle of -4.degree. to 50.degree., -1.degree. to 40.degree., or
0.1.degree. to 30.degree.. A silicon carbide ingot being out of
such a range may have a high possibility of generating cracks or
defects in the interior, have a high possibility of generating a
load when a wafer is processed, and have a possibility of reducing
a usable effective area and a yield rate.
[0255] Additionally, the angle may be a tilted angle of an edge
linked from one side of the circumference of the rear region 101 to
one side of the front region 102 which is the closest to the one
side of the circumference of the rear, based on a direction
perpendicular to the rear as 0.degree., when viewed in a plane
being in an orthogonal position to the rear 101 and comprising a
diameter of the rear.
[0256] The silicon carbide ingot 100 may have a difference of 0.01
mm to 3 mm, or 0.01 mm to 2.9 mm between a center height and an
edge in the front 102 which is an opposite side based on the rear
101.
[0257] The silicon carbide ingot 100 may have a micropipe density
of 1/cm.sup.2 or less, 0.8/cm.sup.2 or less, 0.59/cm.sup.2 or less,
or 0.1/cm.sup.2 or more.
[0258] The silicon carbide ingot 100 may have a basal plane
dislocation density of 1300/cm.sup.2 or less, of 1100/cm.sup.2 or
less, or of 980/cm.sup.2 or less.
[0259] The silicon carbide ingot may have an etch pit density of
12000/cm.sup.2 or less, or of 10000/cm.sup.2 or less.
[0260] The micropipe density, basal plane dislocation density and
etch pit density may be calculated by cutting the silicon carbide
ingot 100 to prepare a wafer, immersing the wafer in molten
potassium hydroxide (KOH) under conditions of 500.degree. C. and 5
minutes and etching the wafer, and then measuring the defects per
unit area in the surface through an optical microscope, etc.
[0261] When the silicon carbide ingot 100 satisfies the above
defect density range, so that a wafer having few defects can be
provided, and when it is applied to an element, an element having
excellent electrical or optical properties can be manufactured.
[0262] A silicon carbide wafer prepared by cutting the silicon
carbide ingot 100 may have a bow absolute value of 50 .mu.m or
less, 48 .mu.m or less, or 43 .mu.m or less. The bow absolute value
may be 5 .mu.m or more. The bow measurement may be made by the same
method as described in below experimental examples.
[0263] Hereinafter, while embodiments of the present disclosure
will be described in more detail with reference to the accompanying
examples, it is noted that examples are not limited to the
same.
EXAMPLES 1 TO 5
Manufacture of Silicon Carbide Ingot
[0264] As shown, in examples of a silicon carbide ingot
manufacturing system and device, as illustrated in a in FIG. 3, a
silicon carbide ingot powder as a raw material 300 was disposed at
the lower portion 240 of an internal space of the reactor 200, and
a silicon carbide seed crystal 110 was disposed at the upper
portion of an internal space of the reactor 200. The silicon
carbide seed crystal 110 was made of 4H-silicon carbide crystal
having a diameter of 6 inches, and the C plane (000-1 plane) was
fixed to face the silicon carbide raw material in the lower portion
of internal space of the reactor 200. Additionally, a guide 120 was
equipped in an external side of the silicon carbide seed crystal
110, and the guide unit was extended toward a perpendicular
direction facing to a silicon carbide raw material from the silicon
carbide seed crystal 110, and had an inner diameter surface tilted
to the external side by 50.degree. based on the perpendicular
direction.
[0265] After the reactor 200 was sealed and the exterior surface of
the reactor 200 was surrounded by a heat insulating material 400,
the reactor 200 was disposed in a quartz tube 500 equipped with a
heating coil disposed exterior to the reactor 200, which is a
heater 600.
[0266] As illustrated in FIG. 2, the internal space of the reactor
200 was depressurized to be adjusted to a vacuum atmosphere, and
was injected with argon gas to reach 760 torr, wherein the
temperature of the internal space of the reactor 200 was raised to
1600.degree. C. at a rate of 10.degree. C./min. As a pre-growth
process at the same time as decompression, the temperature was
raised at a rate of 3.degree. C./min, and the temperature of the
lower portion of the internal space was set to 2350.degree. C.,
which is the temperature of the maximum heating region of the
heater 600. Thereafter, while maintaining the same conditions, the
silicon carbide ingot was grown under the conditions of the moving
speed, moving time, and moving distance of the heater 600 in Table
1.
[0267] After the growth, the temperature of the internal space of
the reactor 200 was cooled to 25.degree. C. at a rate of 5.degree.
C./min, at the same time, argon gas was injected so that the
pressure in the internal space became 760 torr. Then, the formed
silicon carbide ingot was cut and separated from the seed
crystal.
COMPARATIVE EXAMPLES 1 AND 2
Changing the Moving Speed of Heater
[0268] In the above example, except for changing the moving speed,
moving time, and moving distance of the heater to the conditions
shown in Table 1, it proceeded in the same manner as in the above
embodiment.
EXPERIMENTAL EXAMPLE
Measurement of Growing Angle, and Front and Rear Diameters of the
Manufactured Silicon Carbide Ingot, and Bow Value of Silicon
Carbide Wafer
[0269] In a view of facing the front of silicon carbide ingots
manufactured in respective Examples 1 to 5 and Comparative Examples
1 and 2 to be perpendicular to a growing direction as in FIG. 6, a
maximum height of the front region 102 which is a growth end was
measured by a height gauge, an angle between a line perpendicular
to the rear region 101 from the edge of the rear and an edge line
linking the rear and the front was measured, and a diameter of the
circumference of the front region 102 was measured as illustrated
in Table 1.
[0270] Additionally, silicon carbide ingots manufactured in the
respective Examples 1 to 5 and Comparative Examples 1 and 2 were
cut to have an off angle of 4.degree. with (0001) surface, thereby
preparing a wafer of 360 .mu.m, and a wafer ground by a diamond
wheel or the like was prepared. A bow value of this wafer was
measured through a Flatmaster 200XRA device available from Corning
Tropel and shown in Table 1.
TABLE-US-00001 TABLE 1 Comparative Comparative Item Example 1
Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Moving
0.1 0.1 0.1 0.1 0.2 0 0.05 Speed of Heater (mm/hr) Moving 90 100
100 80 100 0 50 Speed of Heater (hr) Moving 9 10 10 8 2 0 2.5 Speed
of Heater (mm) The Height of 15 15.5 15.5 14 18 12 11 Manufactured
Ingot (mm) Inclination 8 10 5 30 -1 60 61 Angle of the Edge
(.degree.) Db(mm) 150 150.5 150 150 154 150 150 Df(mm) 155 158 152
170 150 184 180 Df/Db 1.03 1.04 1.01 1.13 0.97 1.22 1.14 Bow of 42
48 45 -33 -43 212 128 Manufactured Wafer (.mu.m) Df/Db: The ratio
of a diameter of the circumference of the front (Df) and a diameter
of the rear (Db) in a silicon carbide ingot.
[0271] Referring to Table 1, in examples in which a moving speed of
a heater 600 is 0.1 mm/hr to 0.48 mm/hr, a center height of the
front region which was an opposite side based on the rear region of
an ingot (seed crystal surface) was 14 mm or more, an edge angle of
inclination showed -4.degree. to 50.degree., and a bow absolute
value of a wafer manufactured from an ingot was 50 .mu.m thereby
being verified to be good.
[0272] In cases of comparative examples in which a heater 600 does
not move, or a moving speed of a heater 600 is less than 0.1 mm/hr,
the center height showed a value less than 14 mm, an edge angle of
inclination was more than 50.degree., and a bow value of a wafer
manufactured from a silicon carbide ingot also showed a not good
value.
EXAMPLE A
Manufacture of Silicon Carbide Ingot and Wafer
[0273] Referring to FIG. 4, in an illustrated example of a
manufacturing device of a silicon carbide ingot, a silicon carbide
powder implemented as a raw material 300 was charged in a lower
portion of an internal space of a reactor 200, and a silicon
carbide seed crystal 110 was disposed in an upper portion of the
reactor 200. The silicon carbide seed crystal 110 was composed of
4H-silicon carbide crystal of six inches and C surface ((000-1)
surface) was fixed to face a raw material in a lower portion of an
internal space.
[0274] A reactor 200 was sealed, the exterior of the reactor 200
was surrounded by a heat insulating material 400. The reactor 200
was disposed inside a quartz tube 500 having a heating coil as a
heater 600 equipped in the exterior of the quartz tube 500. The
density of the heat insulating material 400 and the ratio Vc/Vi of
a volume of the reactor Vc and a volume of the circumference part
of a heat insulating material Vi surrounding the external surface
of the reactor 200 was applied as described in below Table 1. Each
volume was measured, or was calculated, through a three-dimension
modeling program or the like.
[0275] The internal space of the reactor 200 was depressurized to
be a vacuum atmosphere, and argon gas was injected to the internal
space to reach a value of 760 torr. Thereafter, the internal space
of the reactor 200 was depressurized again and simultaneously the
temperature of the internal space of the reactor 200 was increased
to a first temperature (1600.degree. C.) at a rate of 7.degree.
C./min to 10.degree. C./min. As a first growing process, heating of
the internal space of the reactor 200 was performed to reach a
second temperature, and a temperature difference of Table 1 at a
rate of 3.degree. C./min to 5.degree. C./min with depressurizing at
the same time. The same condition was maintained to grow a silicon
carbide ingot for 80 to 140 hours.
[0276] After the growth, the temperature of the internal space of
the reactor 200 was cooled to 25.degree. C. at a rate of 5.degree.
C./min to 8.degree. C./min and simultaneously argon or nitrogen gas
was injected to the internal space of the reactor 200 to have a
pressure of 760 torr, thereby cooling a silicon carbide ingot.
[0277] The circumference surface of the cooled silicon carbide
ingot was ground to be processed as a shape having a regular
external diameter, and cut to have any one of an angle among
0.degree., 4.degree., and 8.degree. with (0001) surface of a
silicon carbide ingot, thereby manufacturing a silicon carbide
wafer having a thickness of 360 .mu.m. After that, the silicon
carbide wafer was ground to flatten the thickness, and subsequently
processed by chemical mechanical polishing through silica slurry to
prepare a silicon carbide wafer.
EXAMPLES B TO D, AND COMPARATIVE EXAMPLES A AND B
Manufacture of Silicon Carbide Ingot and Wafer
[0278] In the Example 1, the Vc/Vi, the upper temperature and
temperature difference in the second temperature, and the density
and non-resistivity of the heat insulating material were changed to
be as described in Table A, thereby preparing a silicon carbide
wafer.
TABLE-US-00002 TABLE A Upper Lower Temperature The The Non-
Temperature Temperature Difference Density Resistivity in the in
the in the of Heat of Heat Second Second Second Insulating
Insulating Temperature Temperature Temperature Material Material
Vc/Vi (.degree. C.) (.degree. C.) (.degree. C.) (g/cc) (.OMEGA.m)
Example A 0.1 2125 2330 205 0.15 2.5 .times. 10.sup.-4 Example B
0.3 2123 2330 207 0.16 3.1 .times. 10.sup.-3 Example C 0.5 2128
2330 202 0.17 1.0 .times. 10.sup.-4 Example D 0.7 2134 2330 196
0.17 5.0 .times. 10.sup.-3 Comparative 0.9 2173 2330 157 0.13 9.2
.times. 10.sup.-3 Example A Comparative 1 2198 2330 132 0.29 6.3
.times. 10.sup.-2 Example B Vc: The Volumne of Reactor, Vi: The
Volumne of Heat Insulating Material Circumference Part
EXPERIMENTAL EXAMPLE
Measurement of Micropipe and X-ray Rocking Curve Full Width at Half
Maximum of Silicon Carbide Wafer
[0279] 1) Measurement of Micropipe
[0280] Through a Candela 8520 device available from KLA-Tencor, an
image map was formed with silicon carbide wafers prepared in the
Examples A to D, and Comparative Examples A and B as illustrated in
FIGS. 7 and 8, and the micropipe density thereof was measured.
[0281] 2) Measurement of Rocking Curve Full Width at Half
Maximum
[0282] By applying SmartLab High Resolution X-ray Diffraction
(HRXRD) system available from Rigaku, [11-20] direction of silicon
carbide wafers prepared in the Examples A to D, and Comparative
Example A and B, was fitted to an X-ray route, an angle of an X-ray
source and an X-ray detector was set to be 2.theta. (35.degree. to
36.degree.), and after that an omega (.omega. or .theta. of an
X-ray detector) angle was adjusted to be fitted to an off angle of
a wafer to measure a rocking curve full width at half maximum.
Specifically, an omega angle was 17.8111.degree. based on an off
angle of 0.degree., an omega angle was 13.811.degree. based on an
off angle of 4.degree., an omega angle was 9.8111.degree. based on
an off angle of 8.degree., and the values were shown in Table
B.
TABLE-US-00003 TABLE B Rocking Curve Peak Angle and Full Width MP
Density (/cm.sup.2) at Half Maximum Example A 0.13 17.81.degree.
.+-. 0.2.degree. Example B 0.12 13.81.degree. .+-. 0.08.degree.
Example C 0.06 17.81.degree. .+-. 0.05.degree. Example D 0.18
13.81.degree. .+-. 0.10.degree. Comparative Example A 1.16
17.81.degree. .+-. 1.8.degree. Comparative Example B 8.16
17.81.degree. .+-. 1.7.degree. MP: Micropipe
[0283] Referring to Table A and Table B, in a case of an Example
applying the optimum Vc/Vi, temperature difference, heat insulating
material density, and heat insulating material non-resistivity when
a silicon carbide ingot is manufactured, it can be verified that a
micropipe density is remarkably lowered, and a full width at half
maximum of a rocking curve is small thereby having a more excellent
crystal characteristic. In cases of Comparative Examples A and B,
it can be verified that the curvature, stress occurrence, and the
like become excessive during a growth process of a silicon carbide
ingot, thereby showing a result which is not good in the crystal
quality and defect characteristic.
[0284] While this disclosure includes specific examples, it will be
apparent after an understanding of the disclosure of this
application that various changes in form and details may be made in
these examples without departing from the spirit and scope of the
claims and their equivalents. The examples described herein are to
be considered in a descriptive sense only, and not for purposes of
limitation. Descriptions of features or aspects in each example are
to be considered as being applicable to similar features or aspects
in other examples. Suitable results may be achieved if the
described techniques are performed in a different order, and/or if
components in a described system, architecture, device, or circuit
are combined in a different manner, and/or replaced or supplemented
by other components or their equivalents. Therefore, the scope of
the disclosure is defined not by the detailed description, but by
the claims and their equivalents, and all variations within the
scope of the claims and their equivalents are to be construed as
being included in the disclosure.
* * * * *