WO2013002539A2

WO2013002539A2 - Apparatus and method for growing silicon carbide single crystal

Info

Publication number: WO2013002539A2
Application number: PCT/KR2012/005045
Authority: WO
Inventors: Young Shol Kim; Sun Hyuk Bae; Sung Wan Hong
Original assignee: SK Innovation Co Ltd
Current assignee: SK Innovation Co Ltd
Priority date: 2011-06-29
Filing date: 2012-06-26
Publication date: 2013-01-03
Anticipated expiration: 2013-12-29
Also published as: JP5979739B2; JP2014518194A; KR20130002616A; WO2013002539A3

Abstract

Provided are an apparatus and a method for growing a silicon carbide single crystal by solution growth. The apparatus for growing a silicon carbide single crystal includes: a reaction chamber that is in a predetermined pressure state; a crucible that is provided in the reaction chamber, includes silicon (Si) or silicon carbide (SiC) powders or a mixture thereof charged therein, includes a silicon carbide seed provided at an upper portion of an inner side thereof and growing a silicon carbide and a seed connection bar extended from the silicon carbide seed, and is made of a graphite material; and a heating element that heats the crucible. An inner portion of the crucible is provided with at least one protrusion jaws, at least some or all of which are formed along an inner peripheral surface of the crucible, wherein the protrusion jaw is made of the graphite material.

Description

APPARATUS AND METHOD FOR GROWING SILICON CARBIDE SINGLE CRYSTAL

The present invention relates to an apparatus and a method for growing a silicon carbide single crystal by solution growth, and more particularly, to an apparatus and a method for growing a silicon carbide single crystal by solution growth at a high speed by allowing carbon contained in a graphite crucible to be smoothly dissolved in a silicon solution which is a main material.

As the next generation semiconductor material having characteristics more excellent than those of silicon that has been currently used most commonly as a semiconductor material, research into compound semiconductor materials such as a silicon carbide (SiC), a gallium nitride (GaN), a aluminum nitride, and the like, has been widely conducted. Among them, the silicon carbide has excellent mechanical strength, excellent thermal and chemical stability, significantly high thermal conductivity of 4W/cm² or more, and an operation limit temperature of 650 ℃ or less, which is significantly higher than 200 ℃ corresponding to an operation limit temperature of the silicon. Further, since all of the silicon carbides having crystal structures of a 3C silicon carbide, a 4H silicon carbide, and a 6H silicon carbide have a bandgap of 2.5 eV or more which is two times or more higher than that of the silicon, they are significantly excellent as a semiconductor material for a high power and low loss converting apparatus, such that they have been recently spotlighted as a semiconductor material for an optical semiconductor and power conversion, such as a light emitting diode (LED).

Generally, as a method for growing a silicon carbide single crystal, there are the Acheson method of allowing carbon and silica to react with each other in a high temperature electric furnace of 2000 ℃ or more and a sublimation method of sublimating a silicon carbide (SiC) raw material at a high temperature of 2000 ℃ or more to grow a single crystal. In addition to the above-mentioned methods, a method of chemically depositing a gas source has been used.

However, in the case of the Acheson method, it is very difficult to obtain a silicon carbide single crystal having high purity, and in the case of the chemical vapor deposition method, a single crystal may be grown only in a level having a limited thickness such as a thin film. Therefore, research into the sublimation method of sublimating a silicon carbide at a high temperature to grow a crystal has been mainly conducted. However, the sublimation method also has a limitation in view of a production cost since the sublimation method is generally performed at a high temperature of 2200 ℃ or more and it is more likely that several faults such as a micropipe and a stacking fault will be generated.

In order to solve this problem of the sublimation method, a solution growth method to which the Czochralski method (a crystal pulling method) is applied has been introduced. The Czochralski method is a method of growing a single crystal from a melt. A shape or a property of the crystal is determined according to a pulling rate (a growth speed), a rotation speed, a temperature gradient, or a crystal orientation. In the solution growth method for growing a silicon carbide single crystal, generally, silicon or silicon carbide powders are charged in a graphite crucible and a temperature is then raised from 1600 ℃ to a high temperature of 1900 ℃ to allow crystals to be grown from a surface of a silicon carbide seed positioned at an upper portion of the furnace. However, in the case of this method, a crystal growth speed is 50 μm/hr which is significantly low, such that economic efficiency is low.

In Japanese Patent Laid-Open Publication No. 2004-2173, in addition to silicon, titanium (Ti) or manganese (Mg) was mixed with silicon (Si) in a predetermined ratio to increase a crystal growth speed.

Further, in Japanese Patent Laid-Open Publication No. 2006-143555, in addition to silicon, iron (Fe) or cobalt (Co) was used together with silicon (Si) in a predetermined ratio to increase a crystal growth speed. In these methods, metals other than silicon are mixed with silicon to form a eutectic point, thereby increasing solubility of carbon in a silicon solution to increase a silicon carbide single crystal speed. However, there is still a limitation in that an area contacting a metal melt in an internal surface area of the graphite crucible used as a carbon source is small.

Further, in the case of the solution growth method for growing a silicon carbide single crystal, as a supply source of carbon for growing a crystal, a graphite crucible is generally used. That is, carbon atoms composing the graphite crucible are separated in a liquid state and then spread in a solution. Some of the spread carbon atoms move to a silicon carbide single crystal growth portion, such that a single crystal is grown. However, a difference is generated between a carbon concentration in the vicinity of a crucible to which the carbon atoms are supplied and a carbon concentration in the vicinity of a single crystal growth portion at which a carbon atom is synthesized as a silicon carbide to thereby disappear. Therefore, it is required to allow a carbon concentration in a solution in the crucible within a closed growth furnace operated at a high temperature to be uniform to actually increase a carbon concentration in the vicinity of the single crystal growth portion. To this end, similar to a method generally used in the Czochralski method, a seed fixing bar to which a seed is fixed is rotated and/or a crucible is rotated to increase uniformity of a carbon concentration in a solution.

An object of the present invention is to provide an apparatus and a method for growing a silicon carbide single crystal capable of growing the silicon carbide single crystal at a more rapid speed.

In one general aspect, an apparatus for growing a silicon carbide single crystal includes: a reaction chamber that is in a predetermined pressure state; a crucible that is provided in the reaction chamber, includes silicon (Si) or silicon carbide (SiC) powders or a mixture thereof charged therein, includes a silicon carbide seed provided at an upper portion of an inner side thereof and growing a silicon carbide and a seed connection bar extended from the silicon carbide seed, and is made of a graphite material; and a heating element that heats the crucible, wherein an inner portion of the crucible is provided with at least one protrusion jaws, at least some or all of which are formed along an inner peripheral surface of the crucible, the protrusion jaw being made of the graphite material.

Some or all of the protrusion jaws may be formed in a structure in which they do not impede a flow of a silicon solution charged in the crucible, for example, a donut shape.

The silicon carbide seed may be provided so as to be rotatable with respect to the crucible with the aid of the seed connection bar. In addition, the silicon carbide seed may be provided so as to be vertically movable with respect to the crucible with the aid of a seed connection bar. Temperature distribution in the crucible may be easily controlled by a structure in which the silicon carbide seed may rotate and vertically move.

The apparatus may further include a rotation support that is disposed beneath the crucible to rotate the crucible. The crucible itself disposed in the reaction chamber may rotate by the rotation support, such that silicon (Si) and carbon filled in the crucible may more rapidly contact each other, thereby increasing a growth speed of the silicon carbide single crystal.

The heating element may be disposed at any plate in the vicinity of the crucible, preferably, be disposed along an outer peripheral surface of the crucible in order to provide a more smooth flow through the protrusion jaw provided in the crucible. As the heating element, any heating element having heating characteristics or performing a heating operation, typically, a resistive heating element or an induction heating type heating element may be used. A temperature gradient in the crucible by the heating element may be 5℃/cm² or more in a vertical direction.

An inner portion of the reaction chamber may be filled with inert gas such as Argon or Helium gas and may be maintained at pressure of 0.3 to 50 kgf/cm². In order to maintain this pressure, for example, a vacuum pump and a gas cylinder for controlling the atmosphere are connected to the reaction chamber through a valve. Those skilled in the art aware of the present specification may recognize various other units for maintaining the atmosphere of the reaction chamber.

A bottom surface of an inner portion of the crucible may be further provided with a wing shaped assisting tool inducing a fluid flow in a predetermined direction and made of the graphite material. The wing shaped assisting tool serves to allow a fluid flow by rotation of the silicon carbide seed and/or a fluid flow according to rotation of the crucible by the rotation support provided beneath the crucible to be selectively directed toward one direction to give a material such as carbon, or the like, faster and more contact opportunities with the silicon carbide seed, thereby increasing a formation speed of the silicon carbide single crystal.

According to the present invention, a carbon concentration in the vicinity of a silicon carbide seed increases, such that a growth speed of a silicon carbide single crystal increases.

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view schematically showing main parts of an apparatus for growing a silicon carbide single crystal according to a preferable embodiment of the present invention.

FIG. 2 is a partially cut-away perspective view showing a portion of an internal shape of a crucible shown in FIG. 1 and made of a graphite material.

FIG. 3 is a cross-sectional view schematically showing main parts of an apparatus for growing a silicon carbide single crystal according to a more preferable embodiment of the present invention.

FIG. 4 is a partially cut-away perspective view showing a portion of an internal shape of a crucible provided with a wing shaped assisting tool and made of a graphite material.

[Detailed Description of Main Elements]

10: Reaction Chamber 30: Crucible (made of Graphite Material)

32: Silicon Carbide Seed 34: Seed Connection Bar

38: Protrusion Jaw 50: Heating Element

90: Wing Shaped Assisting Tool

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. However, in describing the present invention, a description of a well-known function or configuration will be omitted in order to make the gist of the present invention obvious.

FIG. 1 schematically shows main parts of an apparatus for growing a silicon carbide single crystal according to a preferable embodiment of the present invention; and FIG. 2 is a partially cut-away perspective view schematically showing a portion of an internal shape of a crucible made of a graphite material.

Referring to FIGS. 1 and 2, the apparatus 1 for growing a silicon carbide single crystal according to the preferable embodiment of the present invention is configured to include a reaction chamber 10, a crucible 30 provided in the reaction chamber 10, and a heating element 50 heating the crucible 30. An inner portion of the crucible 30 is provided with at least one protrusion jaws 38, at least some or all of which are formed along an inner peripheral surface of the crucible 30, as shown FIGS. 1 and 2, wherein the protrusion jaw 38 is made of a graphite material.

The reaction chamber 10 is maintained in a vacuum state and is then filled with inert gas such as Argon or Helium, and is controlled so as to have pressure of a level of 0.3 to 50 kgf/cm². In order to maintain this atmosphere, although not shown in FIGS. 1 and 2, a vacuum pump and a gas cylinder for controlling the atmosphere are connected to the reaction chamber 10 through a valve. Those skilled in the art aware of the present specification may recognize various other units for maintaining the atmosphere of the reaction chamber.

The crucible 30 is provided in the reaction chamber 10, as described above, and includes silicon (Si) or silicon carbide (SiC) powders or a mixture thereof charged therein. The crucible 30 may be made of a graphite material and be utilized as a supply source of carbon in itself.

An upper portion of an inner side of the crucible 30 is provided with a silicon carbide seed 32 growing a silicon carbide with the aid of a seed connection bar 34, as shown in FIG. 1. The seed connection bar 34 is provided so as to be rotatable with respect to an upper end portion of the crucible 30, if needed. In addition, the seed connection bar 34 is provided so as to be vertically movable with respect to an upper end portion of the crucible 30, if needed. Therefore, the silicon carbide seed 32 is also provided so as to be rotatable and provided so as to be vertically movable, if needed, as a single crystal grows. Although not shown in FIGS. 1 and 2, this configuration will be obvious to those skilled in the art aware of the present specification.

An outer peripheral surface of the crucible 30 is provided with the heating element 50, as shown in FIG. 1. This heating element 50 may be any heating element having heating characteristics. According to the present invention, a resistive heating element or an induction heating type heating element may be used.

The inner portion of the crucible 30 is provided with at least one protrusion jaws 38, at least some or all of which are formed along an inner peripheral surface of the crucible 30, wherein the protrusion jaw 38 is made of the graphite material. The protrusion jaw 38 made of the graphite material may be formed with a plurality of protrusions or pores in order to give more contact opportunities with a silicon containing solution filled in the crucible 30. This protrusion structure and pore structure are also included in a configuration of the present invention. This protrusion jaw 38 allows more carbons to be dissolved in the silicon containing solution to increase a carbon concentration in the vicinity of a portion at which the single crystal is grown, thereby increasing a growth speed of the silicon carbide single crystal.

The protrusion jaw 38 becomes a carbon supply source in itself. In addition, a contact surface increases through inductive contact or forcible contact of the silicon and additives generated by heating of the crucible 30 by the heating element 50, rotation of the silicon carbide seed 32, if needed, and/or rotation of a rotation support 40 to be described below, such that an amount of carbon supply source increases, thereby further increasing a supply amount and speed of carbon supply source. In this case, a carbon dissolution is increased from the protrusion jaw 30 as well as an inner surface of the crucible 30, and a carbon concentration in the vicinity of a crystal growth portion of the silicon carbide seed 32 further increases by a spiral flow, thereby increasing a growth speed of the silicon carbide single crystal.

In addition, a lower portion of the crucible 30 is provided with the rotation support 40. This rotation support 40 may rotate, if needed, to allow the crucible to rotate at a predetermined speed. The carbon from the crucible 30 and the carbon from the protrusion jaw 38 formed in the crucible 30 are rapidly dissolved in the silicon containing solution by this rotation and the carbon concentration in the vicinity of the silicon carbide seed 32 increases by this rotation, such that the growth speed of the silicon carbide single crystal further increases.

FIG. 3 schematically shows main parts of an apparatus for growing a silicon carbide single crystal according to a more preferable embodiment of the present invention; and FIG. 4 shows a flow of a fluid induced through a wing shaped assisting tool made of a graphite material and an internal shape of a crucible.

Referring to FIGS. 3 and 4, the apparatus for growing a silicon carbide single crystal according to the more preferable embodiment of the present invention further includes the wing shaped assisting tool 90 formed at the bottom of the crucible 30 and made of the graphite material, in addition to the components of the apparatus 1 for growing a silicon carbide single crystal according to the preferable embodiment of the present invention described above.

Although the wing shaped assisting tool 90 made of the graphite material and pertaining to a partial configuration of the present invention is provided together with the above-mentioned protrusion jaw 38 in the present invention, it may be recognized by those skilled in the art sufficiently aware of the present specification that the wing shaped assisting tool 90 made of the graphite material may be singly provided without the protrusion jaw 38 formed along the inner peripheral surface of the crucible.

Again referring to FIGS. 3 and 4, the wing shaped assisting tool 90 made of the graphite material and pertaining to a partial configuration of the present invention is provided at the bottom of the crucible in order to induce a fluid flow in a predetermined direction. The wing shaped assisting tool 90 may be singly provided or provided together with the above-mentioned protrusion jaw 38. In the case in which the wing shaped assisting tool 90 is provided together with the above-mentioned protrusion jaw 38, the wing shaped assisting tool 90 may be provided in parallel with the protrusion jaw 38 or be separately provided in a state in which it is spaced apart from the protrusion jaw 38 provided at the lowermost portion by a predetermined distance.

The wing shaped assisting tool 90 is configured so that a fluid may flow in one direction, particularly as shown in FIG. 4. Further, since the wing shaped assisting tool 90 is made of the graphite material, it is used as a carbon supply source in itself. In the case in which a rotation flow is generated by heating by the heating element 50, rotation of the silicon carbide seed 32 and/or the rotation support 40, the wing shaped assisting tool 90 as described above capable of inducing a unidirectional flow further doubles the rotation flow to increase the carbon concentration in the vicinity of the silicon carbide seed 32. Even in the case in which the rotation flow is not generated by the rotation of the silicon carbide seed 32 and/or the rotation support 40, the wing shaped assisting tool 90 induces the fluid flow generated by the heating of the crucible 30 by the heating element 40 in one direction to increase the carbon concentration in the vicinity of the silicon carbide seed 32, thereby making it possible to increase the carbon concentration in the vicinity of a portion at which the silicon carbide single crystal is grown. Although only a structure having two wings is shown as the wing shaped assisting tool 90 in the present invention, the number and the shape of wings are not limited to those of wings shown in FIGS. 3 and 4.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, such modifications, additions and substitutions should also be understood to fall within the scope of the present invention.

Claims

An apparatus for growing a silicon carbide single crystal, comprising:

a reaction chamber that is in a predetermined pressure state;

a crucible that is provided in the reaction chamber, includes silicon (Si) or silicon carbide (SiC) powders or a mixture thereof charged therein, includes a silicon carbide seed provided at an upper portion of an inner side thereof and growing a silicon carbide and a seed connection bar extended from the silicon carbide seed, and is made of a graphite material; and

a heating element that heats the crucible,

wherein an inner portion of the crucible is provided with at least one protrusion jaws, at least some or all of which are formed along an inner peripheral surface of the crucible, the protrusion jaw being made of the graphite material.
The apparatus of claim 1, wherein the crucible is further provided with a wing shaped assisting tool formed under the protrusion jaw, inducing a fluid flow in a predetermined direction, and made of the graphite material.
The apparatus of claim 2, wherein at least some of the protrusion jaws have a donut shape.
The apparatus of claim 1 or 2, wherein the silicon carbide seed is provided so as to be rotatable with respect to the crucible with the aid of the seed connection bar.
The apparatus of claim 1 or 2, further comprising a rotation support that is disposed beneath the crucible to rotate the crucible.
The apparatus of claim 1 or 2, wherein the heating element is disposed on an outer peripheral surface of the crucible.
The apparatus of claim 6, wherein the heating element is a resistive heating element or an induction heating type heating element.
The apparatus of claim 1 or 2, wherein a temperature gradient in the crucible by the heating element is 5℃/cm² or more in a vertical direction.
The apparatus of claim 1 or 2, wherein an inner portion of the reaction chamber is filled with Argon or Helium gas and has a degree of vacuum of 0.3 to 50 kgf/cm².