CN113512758A

CN113512758A - Silicon carbide ingot, method of manufacturing the same, and system for manufacturing silicon carbide ingot

Info

Publication number: CN113512758A
Application number: CN202011099174.XA
Authority: CN
Inventors: 张炳圭; 朴钟辉; 梁殷寿; 崔正宇; 高上基; 具甲烈; 金政圭
Original assignee: SKC Co Ltd
Current assignee: Sanik Co.
Priority date: 2020-04-09
Filing date: 2020-10-14
Publication date: 2021-10-19

Abstract

The present invention relates to a silicon carbide ingot, a method of manufacturing the same, and a system for manufacturing the same, in which a temperature distribution inside a reaction vessel is changed according to the growth of the ingot by moving a heating unit at a prescribed speed under a step of formally growing the ingot during the manufacturing of the silicon carbide ingot.

Description

Silicon carbide ingot, method of manufacturing the same, and system for manufacturing silicon carbide ingot

Technical Field

The present invention relates to a silicon carbide ingot, a method of manufacturing the same, and a system for manufacturing the silicon carbide ingot.

Background

Silicon carbide has attracted attention as a semiconductor material because it has excellent heat resistance and mechanical strength, and is physically and chemically stable. Recently, as a substrate for high power devices and the like, demand for a silicon carbide single crystal substrate is increasing.

Examples of the method for producing a silicon carbide single crystal include Liquid Phase Epitaxy (LPE), Chemical Vapor Deposition (CVD), and Physical Vapor Transport (PVT). Wherein, in the physical vapor transport method, a silicon carbide raw material is placed inside a crucible, a seed crystal formed of a silicon carbide single crystal is placed at the upper end of the crucible, and then the crucible is heated by an induction heating manner to sublimate the raw material, thereby growing the silicon carbide single crystal on the seed crystal.

The physical vapor transport method is most widely used because it can produce silicon carbide in the form of an ingot due to its high growth rate. However, during the induction heating of the crucible, the temperature distribution inside the crucible is changed according to the temperature gradient condition, the relative position of the heating unit, and the temperature difference between the upper and lower portions of the crucible, and thus the quality of the manufactured silicon carbide ingot may be affected.

Therefore, in order to improve the crystal quality of the silicon carbide ingot and ensure the reproducibility of the manufactured ingot, it is necessary to sufficiently consider factors that may affect the temperature distribution inside the crucible in the growing step.

The above background is technical information possessed by the inventors for the derivation of the present invention or acquired in the derivation process, and thus is not necessarily a known technique disclosed to the public before the application of the present invention.

As related prior art, "large diameter single crystal growth apparatus and growth method using the same" are disclosed in Korean laid-open patent publication No. 10-2013-0124023.

Disclosure of Invention

An object of the present invention is to provide a method of manufacturing a silicon carbide ingot and a system for manufacturing a silicon carbide ingot, in which a temperature distribution inside a reaction vessel is changed according to the growth of the ingot by moving a heating unit at a prescribed speed in a step of growing the ingot formally in the manufacturing process of the silicon carbide ingot.

An object of the present invention is to provide a method of manufacturing a silicon carbide ingot, which minimizes a height deviation between a center and an edge of the silicon carbide ingot and improves crystal quality.

In order to achieve the above object, a method of manufacturing a silicon carbide ingot of an embodiment includes: a preparation step of adjusting an inner space of a reaction vessel in which a silicon carbide raw material and a seed crystal are placed to a high vacuum atmosphere, a proceeding step of injecting an inert gas into the inner space and heating up by a heating unit surrounding the reaction vessel to sublimate the silicon carbide raw material to induce growth of a silicon carbide ingot on the seed crystal, and a cooling step of cooling the temperature of the inner space to room temperature; the performing step includes a process of moving the heating unit; the heating unit is moved so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr.

In one embodiment, the performing step comprises a pre-growth process and a growth process in sequence; the pre-growth process comprises the following steps in sequence: a first process of changing the high vacuum atmosphere in the preparation step to an inert atmosphere, a second process of increasing the temperature of the internal space using the heating unit, and a third process of reducing the pressure of the internal space to reach a growth pressure and increasing the temperature to change the temperature of the internal space to a growth temperature; the growth process is a process of maintaining the inner space at the growth temperature and the growth pressure and inducing the ingot to grow, and the movement of the heating unit may be performed during the growth process.

In an embodiment, the maximum heating area is an area corresponding to a position of a center of the heating unit in the inner space, and the temperature of the maximum heating area may be 2100 ℃ to 2500 ℃.

In one embodiment, the inner space has a secondary heating area having a temperature 110 to 160 ℃ lower than that of the maximum heating area, and the heating unit is movable to maintain the temperature of the secondary heating area.

In an embodiment, the temperature difference is a difference between an upper temperature of the inner space and a lower temperature of the inner space, and the temperature difference may be 40 ℃ to 60 ℃ in the first process.

In an embodiment, the total moving distance of the heating unit may be 10mm or more.

In an embodiment, the temperature difference is a difference between an upper temperature of the inner space and a lower temperature of the inner space, and the temperature difference in the growth process may be 70 ℃ to 120 ℃ greater than the temperature difference in the first process.

In one embodiment, the silicon carbide ingot may have a difference between a height of a center and a height of an edge of a front surface, which is an opposite surface, on a back surface basis of 0.01mm to 3mm, and a maximum height in a direction perpendicular to the back surface may be 15mm or more.

In one embodiment, the silicon carbide boule may have a micropipe density of 1/cm²Hereinafter, the basal plane dislocation density may be 1300/cm²Hereinafter, the etch pit density may be 12000/cm²The following.

In order to achieve the above object, a silicon carbide ingot according to an embodiment may have a difference between a height of a center and a height of an edge of a front surface as an opposite surface of 0.01mm to 3mm based on a back surface, a maximum height in a direction perpendicular to the back surface of 15mm or more, and a micropipe density of 1/cm²Hereinafter, the basal plane dislocation density may be 1300/cm²Hereinafter, the etch pit density may be 12000/cm²The following.

To achieve the above object, a system for manufacturing a silicon carbide ingot of an embodiment includes: a reaction vessel having an inner space, a heat insulating material disposed on an outer surface of the reaction vessel to surround the reaction vessel, and a heating unit for adjusting a temperature of the reaction vessel or the inner space; the silicon carbide seed crystal is positioned at the upper part of the inner space, and the raw material is positioned at the lower part of the inner space; comprises a moving unit for changing the relative position between the heating unit and the reaction vessel in the vertical direction; and growing a silicon carbide ingot from the seed crystal; the heating unit is moved so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr.

In an embodiment, the maximum heating area is an area corresponding to a position of a center of the heating unit in the inner space, and a temperature when the heating unit moves may be 2100 ℃ to 2500 ℃ on the basis of the maximum heating area; the secondary heating area is positioned at the upper part of the inner space; the secondary heating region is an inner region of the heating unit, the inner region having a predetermined length from both ends of the heating unit toward the center thereof with reference to an arbitrary line connecting the silicon carbide raw material and the seed crystal; the temperature of the secondary heating zone may be a temperature 110 to 160 ℃ lower than the temperature of the maximum heating zone.

A method of manufacturing a silicon carbide ingot, a system for manufacturing a silicon carbide ingot, and the like of an embodiment minimize a height deviation between the center and the edge of the manufactured silicon carbide ingot and improve crystal quality by adjusting the relative positions of a reaction vessel and a heating unit at a prescribed speed in a growth step of the silicon carbide ingot.

The silicon carbide ingot of an embodiment has advantages in that the defect density of micropipes, basal plane dislocations, etch pits, etc. is low and cracks or polymorphism are almost generated.

Drawings

Fig. 1 is a conceptual diagram showing an example of a manufacturing apparatus to which the manufacturing method of a silicon carbide ingot according to the present invention is applied.

Fig. 2 is a graph showing temperature, pressure and argon pressure trends with respect to time in the method for manufacturing a silicon carbide ingot according to the present invention.

Fig. 3 is a conceptual view showing an ingot manufactured by the manufacturing method of a silicon carbide ingot according to the present invention and a height difference of a front surface of the ingot.

Fig. 4 is a conceptual diagram illustrating an example of an apparatus for manufacturing a silicon carbide ingot according to the present invention.

Fig. 5 is a conceptual diagram illustrating a part of an apparatus for manufacturing a silicon carbide ingot according to the present invention.

Description of reference numerals

100: silicon carbide ingot

110: seed crystal

200: reaction vessel

210: body

220: cover

230: upper part of the inner space

240: lower part of the inner space

300: raw materials

400: heat insulating material

500: reaction chamber and quartz tube

600: heating unit

700: vacuum exhaust device

800: mass flow controller

810: pipeline

Detailed Description

The embodiments are described in detail below with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention. However, the embodiments of the present invention can be realized by various different embodiments, and are not limited to the embodiments described in the present specification. Throughout the specification, like parts are denoted by the same reference numerals.

In this specification, unless otherwise specified, when a structure "includes" another structure, it means that the other structure may be included without excluding the other structure.

In this specification, when a structure is "connected" to another structure, this includes not only the case of "directly connecting" but also the case of "connecting by connecting other structures therebetween".

In this specification, B on a means that B is in direct contact with a or B on a in the case where another layer is provided between B and a, and cannot be restrictively interpreted as B being in contact with the surface of a.

In the present specification, the term "combination thereof" included in the markush expression indicates a mixture or combination of one or more selected from the group consisting of a plurality of structural elements described in the markush expression, and indicates that the mixture or combination includes one or more selected from the group consisting of the plurality of structural elements.

In the present specification, the expression "a and/or B" means "a or B or a and B".

In this specification, unless otherwise specified, the terms "first", "second" or "a", "B", etc. are used to distinguish the same terms.

In this specification, the singular expressions include the plural expressions unless the different meanings are explicitly stated in the sentence.

In studying a method of minimizing the occurrence of defects and cracks of a silicon carbide ingot and improving crystal quality, the inventors invented a method of manufacturing a silicon carbide ingot, which can change the relative positions of a reaction vessel and a heating unit at a prescribed rate in a step of growing the silicon carbide ingot, and provided examples.

Method for producing silicon carbide ingot

In order to achieve the above object, a method of manufacturing a silicon carbide ingot of an embodiment includes: preparing step Sa, adjusting the internal space of the reaction vessel 200 in which the silicon carbide raw material 300 and the seed crystal 110 are placed to a high vacuum atmosphere, performing steps Sb, S1, injecting an inert gas into the internal space, and heating by the heating unit 600 surrounding the reaction vessel to sublimate the silicon carbide raw material to induce growth of the silicon carbide ingot 100 on the seed crystal, and cooling step S2, cooling the temperature of the internal space to room temperature; the performing step includes a process of moving the heating unit, which moves so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr.

The heating unit 600 and the reaction vessel 200 may be installed to be able to change relative positions in a vertical direction. The relative position may be changed by the moving unit, and may be changed by moving more than any one of the heating unit and the reaction vessel. Changing the relative position by movement of the heating unit as compared to movement of the position of the reaction vessel facilitates growth of a stable silicon carbide ingot.

Fig. 1, 4 and 5 show examples of manufacturing apparatuses of silicon carbide ingots. The method of manufacturing a silicon carbide ingot of the embodiment will be described with reference thereto.

The preparation step Sa is a step of disposing the raw material 300 and the silicon carbide seed crystal 110 in a reaction vessel 200 having an inner space so as to face each other and adjusting to a high vacuum atmosphere.

In the preparation step Sa, the pressure in the internal space may be reduced to 50 torr or less, 10 torr or less, 5 torr or less, and 1 torr or more. When subjected to such a preparation step of a high vacuum atmosphere, an ingot reduced in defects can be produced.

The silicon carbide seed crystal 110 of the preparation step Sa may be suitably sized in accordance with the target ingot, and for example, a silicon carbide wafer may be used. And the C-face ((000-1) face) of the silicon carbide seed crystal may face the raw material 300.

The silicon carbide seed crystal 110 of the preparation step Sa may contain 4H silicon carbide having 4 inches or more, and may also contain 4H silicon carbide having 6 inches or more.

When the silicon carbide seed crystal 110 is in the form of a seed holder (not shown), the silicon carbide seed crystal may further include an adhesive layer disposed on the back side. When the silicon carbide seed crystal is in a form that is not directly attached to the seed holder, the silicon carbide seed crystal may further include a protective layer disposed on the back surface. In this case, the growth of the silicon carbide ingot having less defects can be induced.

The silicon carbide raw material 300 of the preparation step Sa may be used in a powder shape having a carbon source and a silicon source, and the raw material may include a silicon carbide powder.

The silicon carbide raw material 300 may include silicon carbide powders that are necked down to each other or silicon carbide powders obtained by surface carbonization treatment thereof. In this case, more efficient growth of silicon carbide may be aided by inducing sublimation of more stable silicon carbide during growth.

The reaction vessel 200 of the preparation step Sa may be a vessel suitable for a silicon carbide ingot growth reaction, and specifically, a graphite crucible may be used. For example, the reaction vessel may include a body 210 having an inner space and an opening, and a cover 220 corresponding to the opening to close the inner space. The crucible cover may further include a seed crystal holder formed integrally with or separately from the crucible cover, and the silicon carbide seed crystal may be held by the seed crystal holder such that the silicon carbide seed crystal 110 and the silicon carbide raw material 300 face each other.

The reaction vessel 200 of the preparation step Sa may include a heat insulating material 400 placed on an outer surface to surround the reaction vessel, and the heat insulating material may be in contact with the reaction vessel or have a prescribed distance. An insulating material surrounding the reaction vessel may be located in the reaction chamber 500 such as a quartz tube, and the temperature of the inner space of the reaction vessel 200, etc. may be controlled by the insulating material and the heating unit 600 disposed outside the reaction chamber.

The porosity of the thermal insulation material 400 in the preparation step Sa may be 72% to 95%, 75% to 93%, or 80% to 91%. When the heat insulating material satisfying the porosity is used, the generation of cracks of the grown silicon carbide ingot can be further reduced.

The heat insulating material 400 in the preparation step Sa may have a compressive strength of 0.2MPa or more, may have a compressive strength of 0.48MPa or more, and may have a compressive strength of 0.8MPa or more. The thermal insulation material may have a compressive strength of 3MPa or less, or 2.5MPa or less. When the heat insulating material has such compressive strength, its thermal/mechanical stability is excellent and the occurrence probability of ash (ash) is reduced, so that a silicon carbide ingot having more excellent quality can be produced.

The heat insulating material 400 of the preparation step Sa may include a carbon-based felt, and specifically, may include a graphite felt, a rayon-based graphite felt, or an asphalt-based graphite felt.

The reaction chamber 500 may include: a vacuum exhaust device 700 connected to the inside of the reaction chamber for adjusting the degree of vacuum inside the reaction chamber; a pipe 810 connected to the inside of the reaction chamber for introducing gas into the inside of the reaction chamber; and a mass flow controller 800 for controlling the gas. By these, the flow rate of the inert gas can be adjusted in the subsequent growth step and cooling step.

In the performing step Sb, S1, an inert gas is injected into the inner space and the raw material is sublimated by adjusting the temperature, pressure and atmosphere of the inner space, thereby inducing growth of the silicon carbide ingot 100 on the silicon carbide seed crystal 110.

In the performing step Sb, S1, the internal space may be substantially changed to an inert gas atmosphere. The inert gas atmosphere may be formed by, but not limited to, injecting an inert gas after depressurizing the inner space of the reaction vessel in the atmospheric atmosphere and inducing it to be substantially a vacuum atmosphere after the process of placing the silicon carbide raw material 300 and the seed crystal 110, etc.

The inert gas atmosphere in the performing steps Sb and S1 means that the atmosphere in the inner space in the growth step is not an atmospheric atmosphere, but includes the case where: although the atmosphere of an inert gas is mainly used, a small amount of gas is injected for the purpose of doping the silicon carbide ingot. The inert gas atmosphere is suitably an inert gas, which may be, for example, argon, helium or a mixture thereof.

The performing step Sb, S1 may be performed by the heating unit 600 heating the reaction vessel 200 or the inner space of the reaction vessel, or may be performed by performing the heating while or in addition decompressing the inner space to adjust the degree of vacuum, and injecting an inert gas.

The performing steps Sb, S1 induce sublimation of the silicon carbide raw material 300 and growth of the silicon carbide ingot 100 on a surface of the silicon carbide seed crystal 110.

The heating unit 600 may be disposed around the reaction vessel 200 to be installed to be movable in a vertical direction substantially parallel to any line from the silicon carbide seed crystal 110 to the raw material 300, and may include a moving unit for changing a relative position between the heating unit and the reaction vessel in the vertical direction. Accordingly, the relative position between the reaction vessel and the heating unit can be changed, and a temperature gradient of the inner space can be induced. In particular, the heating unit may apply a temperature difference between an upper portion 230 of the interior space and a lower portion 240 of the interior space.

The heating unit 600 may be applied to an induction heating unit formed as a spiral coil along the outer circumferential surface of the reaction vessel 200 or the heat insulating material 400 surrounding the reaction vessel, but is not limited thereto.

The performing steps Sb, S1 may sequentially include a pre-growth process Sb and a growth process S1, and the pre-growth process may sequentially include: a first process Sb1 of changing the high vacuum atmosphere in the preparation step to an inert atmosphere, a second process Sb2 of increasing the temperature of the internal space using the heating unit 600, and a third process Sb3 of decreasing the pressure of the internal space to reach a growth pressure and increasing the temperature to change the temperature of the internal space to a growth temperature.

The growth process S1 is a process of maintaining the inner space at the growth temperature and the growth pressure and inducing the induced ingot to grow.

The first process Sb1 may be performed by injecting an inert gas such as argon. At this time, the pressure of the inner space may be 500 torr to 800 torr.

The second process Sb2 is a process of heating the lower portion 240 of the inner space to a pre-growth start temperature of 1500 ℃ to 1700 ℃. The temperature increase in the second process Sb2 may be performed at a rate of 1 to 10 ℃/min.

In the third process Sb3, the lower part 240 of the inner space may be heated to a growth temperature of 2100 ℃ to 2500 ℃ and decompressed to a growth pressure of 1 torr to 50 torr. The temperature increase in the third process Sb3 may be performed at a rate of 1 to 5 ℃/min.

Within the temperature increase rate and pressure range of the second and third processes, the occurrence of polymorphic forms other than the target crystal can be prevented, and stable growth can be induced.

Referring to fig. 5, the upper portion 230 of the interior space is a region of the interior space near the surface of the silicon carbide seed crystal 110 or ingot and the lower portion 240 of the interior space is a region of the interior space near the surface of the feedstock 300. Specifically, the upper portion 230 of the interior space is a temperature measured at a location about 5mm or more, more specifically about 5mm, below the surface of the silicon carbide seed or ingot, and the lower portion 240 of the interior space is a temperature measured at a location about 10mm or more, more specifically about 10mm, above the surface of the feedstock 300. When the upper portion of the inner space or the lower portion of the inner space is at the same position as viewed in the longitudinal direction of the crucible, and if the temperatures measured at each measurement position are different, the temperature of the central portion is taken as a reference.

In the growth process S1, a process of moving the relative position of the heating unit with respect to the reaction vessel may be included.

The meaning of maintaining the growth pressure in the growth process S1 includes a case where the pressure of the inflow gas is slightly adjusted as necessary within a range where the growth of the silicon carbide ingot is not stopped under the reduced pressure. And, maintaining the growth pressure means that the pressure of the internal space is maintained within a prescribed range within a range in which the growth of the silicon carbide ingot can be maintained.

The pre-growth process Sb may apply a prescribed temperature difference to the upper part 230 of the internal space and the lower part 240 of the internal space, and the temperature difference in the pre-growth start temperature may be 40 ℃ to 60 ℃, or 50 ℃ to 55 ℃. The temperature difference in the growth temperature may be 110 ℃ to 160 ℃ or may be 135 ℃ to 150 ℃. By having the temperature difference as described above, occurrence of a polycrystalline type other than the target crystal can be prevented when the initial silicon carbide ingot is formed, and the ingot can be stably grown.

The temperature increase rate of the third process Sb3 may be lower than the average temperature increase rate of the entire second process Sb2 and third process Sb 3. The entire average temperature-rise temperature of the second process and the third process is a value obtained by dividing the difference between the temperature at the temperature-rise start time point of the second process and the temperature at the third process end time point by the elapsed time, and the temperature-rise rate in the third process means the temperature-rise rate at each time point in the third process.

The heating unit 600 may have a maximum heating area, and the maximum heating area refers to a portion having the highest temperature in the atmosphere of the inner space heated by the heating unit. When the heating unit surrounds the side surface of the reaction vessel in the form of a spiral coil, the inner space corresponding to the center of the heating unit is a maximum heating area. For example, assuming a vertical line (vertical center line) connecting the centers of the silicon carbide raw material 300 and the seed crystal 110 and a surface (heating unit center plane) extending in a horizontal direction from the center of the height of the heating unit, the maximum heating area may be an area where an intersection between the vertical center line and the heating unit horizontal plane is located.

The second and third processes Sb1 and Sb2 may make the maximum heating area of the heating unit the lower portion of the reaction vessel, i.e., the surface 240 of the raw material, and may apply a temperature difference between the upper and lower portions of the inner space to be targeted by changing the winding number and thickness when the heating unit has a spiral coil shape.

The growth process S1, after raising the temperature to the growth temperature in the third process Sb3, formally sublimes the raw material to form a silicon carbide ingot. At this time, the growth temperature may be maintained to form a silicon carbide ingot. The meaning of maintaining the growth temperature does not necessarily mean that it must be performed at a fixed proceeding temperature, but means that silicon carbide is grown in a range where the temperature change is insufficient to stop the growth of the silicon carbide ingot even if the absolute temperature slightly changes.

In the growth process S1, the heating unit is moved so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr. The relative position may be set at a rate of 0.1mm/hr to 0.4mm/hr, or at a rate of 0.2mm/hr to 0.3mm/hr, based on the seed crystal 110. The speed range is a considerably low speed range, and when the relative position is changed at a speed as described above, it is possible to prevent formation of a polycrystalline type other than the target crystal in the grown silicon carbide ingot, and to produce a silicon carbide ingot having fewer defects.

In the growth process S1, the change in the relative position of the heating unit 600 with respect to the reaction vessel 200 and the seed crystal 110 may be performed after the growth temperature is reached, or may be performed 1 to 10 hours after the growth temperature is reached.

In the growth process S1, the upper portion 230 of the inner space may have a secondary heating region having a temperature 110 to 160 ℃ lower than that of the maximum heating region in the reaction vessel. The temperature of the secondary heating zone may be 135 ℃ to 150 ℃ lower than the temperature of the maximum heating zone.

The secondary heating area refers to a portion having a relatively low temperature in the atmosphere of the internal space heated by the heating unit. When the heating unit surrounds the side surface of the reaction vessel in the form of a spiral coil, the secondary heating area may be located above the maximum heating area.

Assuming a vertical line (vertical center line) connecting the centers of the silicon carbide raw material 300 and the seed crystal 110 and a surface (heating unit central plane) extending in a horizontal direction from the center of the height of the heating unit, the secondary heating zone may be a region located between the maximum heating zone and the surface of the silicon carbide seed crystal or ingot, and preferably, at least a portion of the secondary heating zone may overlap with an upper portion of the inner space.

The heating unit 600 may be moved in a vertical direction with reference to the reaction vessel by a moving unit for changing a relative position between the heating unit and the reaction vessel 200 in the vertical direction. That is, the seed crystal 110 placed in the reaction vessel may be moved in a substantially parallel direction with respect to an arbitrary line from the seed crystal to the silicon carbide raw material 300.

The heating unit 600 of the growth process S1 may be lowered and moved at the speed based on the reaction vessel.

The growth temperature in the growth process S1 may be 2100 ℃ to 2500 ℃, or 2200 ℃ to 2400 ℃ based on the maximum heating region. The temperature during the growth process may be 1900 to 2300 ℃ or 2100 to 2250 ℃ based on the upper part 230 of the internal space.

The total moving distance of the heating unit may be 10mm or more, or 15mm or more during the growth process S1. The total moving distance may be 45mm or less and 30mm or less.

The growth process S1 may be performed for 5 to 200 hours, or 75 to 100 hours.

In the pre-growth process Sb and/or the growth process S1, the reaction vessel 200 is rotated about the vertical direction as an axis, and the formation of a more favorable temperature gradient for the growth of the silicon carbide ingot can be induced.

The performing steps Sb and S1 may be performed by adding an inert gas at a predetermined flow rate to the outside of the reaction vessel 200. The inert gas may form a gas flow in the inner space of the reaction vessel 200, and may induce a gas flow in a direction from the raw material substance 300 to the silicon carbide seed crystal. Therefore, a stable temperature gradient of the reaction vessel and the inner space can be formed.

The cooling step S2 is a step of cooling the silicon carbide ingot grown by the performing step under conditions of a prescribed cooling rate and inert gas flow rate.

In the cooling step S2, the cooling may be performed at a rate of 1 to 10 ℃/min, or at a rate of 1 to 5 ℃/min.

In the cooling step S2, the pressure adjustment of the inner space of the reaction vessel 200 may be performed simultaneously with the cooling step, or may be performed separately. The pressure may be adjusted such that the pressure in the interior space is at most 800 torr.

In the cooling step S2, as in the above-described proceeding step, a predetermined flow rate of inert gas may be supplied into the reaction vessel 200. The inert gas may flow in the inner space of the reaction vessel, and the flow may be formed from the raw material substance 300 toward the silicon carbide seed crystal 110.

The cooling step S2 may include: a first cooling process of pressurizing to make the pressure of the inner space of the reaction vessel 200 greater than the atmospheric pressure, and cooling to make the temperature of the inner space 1500 ℃ to 1700 ℃ on the basis of the upper part 230; a second cooling step of cooling the temperature of the inner space to room temperature after the first cooling step.

The recovery of the cooling step S2 may be performed by cutting the back surface of the silicon carbide ingot in contact with the seed crystal 110. The cut silicon carbide ingot exhibits a good height difference between the center and the edge of the grown tip, and may have a reduced defect density. The specific shape and defect density of the silicon carbide ingot will be described below.

System for manufacturing silicon carbide ingot

To achieve the above object, a system for manufacturing a silicon carbide ingot of an embodiment includes: a reaction vessel 200 having an inner space, a heat insulating material 400 disposed on an outer surface of the reaction vessel to surround the reaction vessel, and a heating unit 600 for controlling a temperature of the reaction vessel or the inner space; a silicon carbide seed crystal 110 located in an upper portion of the interior space and a feedstock 300 located in a lower portion of the interior space; comprises a moving unit for changing the relative position between the heating unit and the reaction vessel in the vertical direction; growing a silicon carbide ingot from the seed crystal; by the movement of the heating unit, the heating unit is moved so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr.

The silicon carbide ingot 100 may have a difference between the height of the center and the height of the edge of the front surface, which is the opposite surface, of 0.01mm to 3mm, based on the back surface separated from the silicon carbide seed crystal 110, and the maximum height in the direction perpendicular to the back surface may be 15mm or more.

The Micropipe density of the silicon carbide boule 100 may be 1/cm²Hereinafter, the Basal Plane Dislocation (Basal Plane Dislocation) density may be 1300/cm²Hereinafter, the Etch Pit (Etch Pit) density may be 12000/cm²The following.

Referring to fig. 4, the reaction vessel 200 may include a body 210 having an inner space and an opening, and a cover 220 corresponding to the opening to form the inner space, the other things being the same as those described above.

The material and physical properties of the heat insulating material 400 are the same as those described above.

The system for manufacturing a silicon carbide ingot may include a reaction chamber 500 in which a reaction vessel 200 surrounded by a heat insulating material 400 is placed in the reaction chamber 500. In this case, the heating unit 600 may be disposed outside the reaction chamber to control the temperature of the inner space of the reaction vessel.

The reaction chamber 500 may include: a vacuum exhaust device 700 connected to the inside of the reaction chamber for adjusting the degree of vacuum inside the reaction chamber; a pipe 810 connected to the inside of the reaction chamber for introducing gas into the inside of the reaction chamber; and a mass flow controller 800 for controlling the gas. By these, the flow rate of the inert gas can be adjusted in the growth step and the cooling step.

The heating unit 600, referring to fig. 5, may be moved away at a speed of 0.1mm/hr to 0.48mm/hr, at a speed of 0.1mm/hr to 0.4mm/hr, or at a speed of 0.2mm/hr to 0.3mm/hr, with respect to the relative position of the heating unit to the reaction vessel 200. When the above moving speed is satisfied, even if the ingot is grown and the position of the surface is changed, a stable temperature difference and temperature gradient can be applied, and formation of polycrystals other than the target crystal can be prevented.

The movement of the heating unit 600 may be performed in the proceeding step of subliming the raw material by adjusting the temperature, pressure and atmosphere of the inner space and preparing the silicon carbide ingot grown from the seed crystal, for example, may be performed in the second process, the third process and the growth process as the preceding growth process of the proceeding step, and these steps and processes are the same as described above.

A moving unit for changing a relative position between the heating unit 600 and the reaction vessel 200 in a vertical direction is included, and in the growing step, may be lowered and moved at the speed as shown in fig. 1.

The heating unit 600 may have a maximum heating area located at a lower portion of the inner space. The maximum heating area is an area of the inner space located at a position corresponding to the center of the heating unit. When the heating unit has a spiral coil shape, an inner region of the heating unit having a predetermined length from the center of the heating unit to both ends thereof may be a maximum heating region with reference to an arbitrary line connecting the silicon carbide raw material and the seed crystal 110. The temperature of the maximum heating zone may be 2100 ℃ to 2500 ℃, or 2200 ℃ to 2400 ℃.

The heating unit 600 may be moved such that the temperature of the upper portion 230 of the inner space is 110 to 160 c lower than that of the maximum heating region in the growing step, and may be 135 to 150 c lower. When the heating unit has a spiral coil shape, an upper portion of the inner space may be located above the maximum heating area, i.e., the center. The temperature of the upper portion of the interior space may be 1900 ℃ to 2300 ℃, or 2100 ℃ to 2250 ℃.

The system for manufacturing a silicon carbide ingot may sequentially perform the above preparation step Sa, performing steps Sb, S1, cooling step S2, and the like.

Silicon carbide ingot

In order to achieve the above object, silicon carbide ingot 100 of an embodiment may have a difference between the height of the center and the height of the edge in front of the opposite surface of the ingot, when the back surface cut from silicon carbide seed crystal 110 is taken as a reference, of 0.01mm to 3mm, or 0.01mm to 2.9 mm.

The maximum height of silicon carbide ingot 100 in the direction perpendicular to the back surface may be 15mm or more, 18mm or more, or 21.6mm or more.

The Micropipe density of the silicon carbide boule 100 may be 1/cm²Hereinafter, it may be 0.8/cm²Hereinafter, the concentration may be 0.59/cm²The following.

The Basal Plane Dislocation (Basal Plane Dislocation) density of the silicon carbide crystal ingot 100 may be 1300/cm²Hereinafter, 1100/cm may be used²Hereinafter, it may be 980/cm²The following.

The silicon carbide ingot 100 may have an Etch Pit (Etch Pit) density of 12000/cm²Hereinafter, the concentration may be 10000/cm²The following.

After a wafer is prepared by cutting the silicon carbide ingot 100 and is etched by immersing it in molten potassium hydroxide (KOH) at 500 c for 5 minutes, the micropipe, basal plane dislocation and etch pit density can be calculated by measuring defects per unit area of the surface thereof with an optical microscope or the like.

The silicon carbide ingot 100 is made to satisfy the above defect density range to provide a wafer with few defects, and when it is applied to a device, a device having excellent electrical or optical characteristics can be manufactured.

The present invention will be described in more detail with reference to the following examples. The following examples are merely examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

< example-production of silicon carbide ingot >

As one example of the silicon carbide ingot producing apparatus shown in fig. 4 and 5, silicon carbide powder as a raw material 300 is charged into a lower portion 240 of an inner space of a reaction vessel 200, and a silicon carbide seed crystal is placed in an upper portion 230 of the inner space. At this time, a silicon carbide seed crystal composed of a 6-inch 4H silicon carbide crystal was used and fixed in a conventional manner so that the C face ((000-1) face) was directed toward the silicon carbide raw material in the lower part of the internal space.

The reaction vessel 200 was sealed, and the outside thereof was surrounded by the heat insulating material 400, and then the reaction vessel was set in the quartz tube 500 having the heating coil as the heating unit 600 on the outside.

As shown in fig. 1, the inner space of the reaction vessel 200 was depressurized to adjust to a vacuum atmosphere, and argon gas was injected to make the inner space to 760 torr, and the temperature of the inner space was increased to 1600 c at a rate of 10 c/min with respect to the lower portion. Next, as a preliminary growth process, the temperature was raised at a rate of 3 ℃/min while reducing the pressure, and the temperature of the lower portion of the inner space was at 2350 ℃ of the temperature of the maximum heating area of the heating unit. Then, the silicon carbide ingot was grown under the conditions of the moving speed, time and moving distance of the heating unit shown in table 1 while maintaining the same conditions.

After the growth, the temperature of the inner space was cooled to 25 ℃ at a rate of 5 ℃/min while injecting argon gas so that the pressure of the inner space became 760 torr. Then, the formed silicon carbide ingot is cut to be separated from the seed crystal.

< comparative example-change in moving speed of heating means >

In the above embodiment, the same manner as in the above embodiment was performed except that the moving speed, time, and moving distance of the heating unit were changed to the conditions of table 1.

Experimental example-measurement of the height of the produced silicon carbide ingot, height difference and Presence of cracks >

The front surfaces of the silicon carbide ingots prepared in each example and comparative example were measured for the height of the center of the front surface of the growth tip by a height gauge, the height of the periphery of the silicon carbide ingot was measured, and cracks of the seed surface as a cut surface of the ingot were visually inspected, and the results are shown in table 1.

< Experimental example-measurement of defect Density of wafer >

The silicon carbide ingots of each example and comparative example were cut to have an off angle of 4 ° from the seed surface as a cut surface, and wafer samples having a thickness of 360 μm were prepared.

Dicing was performed in a size of 50mm x 50mm in an area having an outer diameter of 95% compared to the maximum outer diameter of the wafer sample. It was immersed in molten potassium hydroxide (KOH) at 500 ℃ for 5 minutes and etched, and defects on the surface thereof were photographed by an optical microscope or the like. Shell-shaped pits are classified as basal plane dislocations BPD, and black giant hexagonal perforated pits are classified as micropipes MP.

The defect density was determined by randomly designating the 500 × 500 μm region in the sliced wafer sample 12 times, determining the number of defects in each region, and calculating the average number of defects per unit area, and the results are shown in table 1.

[ Table 1]

Ingot height difference: the difference between the height of the center and the height of the edge of the front face of the opposite face with respect to the rear face of the ingot

MP: microtubes, micropipes

BPD: basal Plane Dislocation

EPD: etch Pit, Etch Pit sensitivity

Referring to table 1, in the case of the embodiment in which the moving speed of the heating unit is 0.1mm/hr to 0.48mm/hr, the center height of the front face as the opposite face is 20mm or more based on the back face (front face of the seed crystal) of the ingot, and the difference between the height of the center and the height of the edge is 2mm to 3mm, and the defect density value of the wafer made from the ingot is also good.

In comparative example in which the heating unit did not move or the moving speed was 0.5mm/hr, the center height was 11mm or less, in comparative example 1, cracks were generated on the back surface (front surface of seed crystal) of the ingot, and the defect density value of the wafer made from the ingot was relatively high.

While the preferred embodiments of the present invention have been described in detail, the scope of the appended claims should not be limited thereto, and various modifications and improvements that can be made by those skilled in the art using the basic concept of the present invention defined in the appended claims are also within the scope of the appended claims.

Claims

1. A method for producing a silicon carbide ingot, characterized in that,

the method comprises the following steps:

a preparation step of adjusting the internal space of a reaction vessel in which a silicon carbide raw material and seed crystals are placed to a high vacuum atmosphere,

a step of injecting an inert gas into the inner space and heating up by a heating unit surrounding the reaction vessel to sublimate the silicon carbide raw material to induce growth of a silicon carbide ingot on the seed crystal, and

a cooling step of cooling the temperature of the internal space to room temperature;

the performing step includes a process in which the heating unit moves;

the heating unit is moved so that the relative position with respect to the seed crystal is away from the seed crystal at a speed of 0.1mm/hr to 0.48 mm/hr.

2. A method for producing a silicon carbide ingot as set forth in claim 1 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the performing step sequentially comprises a pre-growth process and a growth process;

the pre-growth process comprises the following steps in sequence:

a first process of changing the high vacuum atmosphere in the preparation step to an inert atmosphere,

a second process of increasing the temperature of the inner space using the heating unit, an

A third process of reducing the pressure of the internal space to reach a growth pressure and raising the temperature to bring the temperature of the internal space to a growth temperature;

the growing process is a process of maintaining the inner space at the growth temperature and the growth pressure and inducing the ingot to grow;

the movement of the heating unit is performed during the growth process.

3. A method for producing a silicon carbide ingot as set forth in claim 2 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the maximum heating area is an area corresponding to a position of the center of the heating unit in the inner space,

the temperature of the maximum heating zone is 2100 ℃ to 2500 ℃.

4. A method for producing a silicon carbide ingot as set forth in claim 3 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the inner space has a secondary heating zone,

the temperature of the secondary heating zone is a temperature 110 to 160 ℃ lower than the temperature of the maximum heating zone,

the heating unit moves to maintain the temperature of the secondary heating area.

5. A method for producing a silicon carbide ingot as set forth in claim 2 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the temperature difference is a difference between an upper temperature of the inner space and a lower temperature of the inner space,

the temperature difference in the first process is 40 ℃ to 60 ℃.

6. A method for producing a silicon carbide ingot as set forth in claim 1 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the total moving distance of the heating unit is more than 10 mm.

7. A method for producing a silicon carbide ingot as set forth in claim 2 wherein the silicon carbide ingot is heated in the presence of a catalyst,

the temperature difference during the growth process is 70 ℃ to 120 ℃ greater than the temperature difference during the first process.

8. A silicon carbide ingot, characterized in that,

comprising a front face and a back face as its opposite face,

the back surface is a surface cut from the seed crystal,

the difference between the height of the center of the front face and the height of the edge is 0.01mm to 3mm based on the rear face, and the maximum height in the direction perpendicular to the rear face is 15mm or more,

the density of the microtubes is 1/cm²The basal plane dislocation density is 1300/cm²The etch pit density was 12000/cm²The following.

9. A system for manufacturing a silicon carbide ingot,

the method comprises the following steps:

a reaction vessel having an interior space,

a heat insulating material disposed on an outer surface of the reaction vessel to surround the reaction vessel, and

a heating unit for adjusting a temperature of the reaction vessel or the inner space;

a silicon carbide seed crystal is located in an upper portion of the interior space,

the raw material is positioned at the lower part of the inner space;

comprises a moving unit for changing the relative position between the heating unit and the reaction vessel in the vertical direction;

growing a silicon carbide ingot from the seed crystal;

10. A system for manufacturing a silicon carbide ingot as set forth in claim 9 wherein the silicon carbide ingot is heated in the furnace,

the temperature of the heating unit during movement is 2100 ℃ to 2500 ℃ on the basis of the maximum heating area;

the secondary heating area is positioned at the upper part of the inner space;

the temperature of the secondary heating zone is a temperature 110 to 160 ℃ lower than the temperature of the maximum heating zone.