KR102609885B1 - Manufacturing apparatus for siliconcarbide single crystal - Google Patents

Abstract

The present invention includes a crucible including an outer peripheral surface,
an induction heating member surrounding the crucible, and
It includes a silicon carbide (SiC) seed crystal member provided inside the crucible,
The crucible includes a material with higher electronic conductivity than the material forming the crucible wrapped around the outer peripheral surface, and provides an apparatus for manufacturing a silicon carbide single crystal including a ring or discontinuous protrusion.

Description

Manufacturing equipment for silicon carbide single crystal {MANUFACTURING APPARATUS FOR SILICONCARBIDE SINGLE CRYSTAL}

The present invention relates to an apparatus for manufacturing silicon carbide single crystals.

Silicon carbide (SiC) single crystal has excellent mechanical strength such as wear resistance, heat resistance, and corrosion resistance, and is widely used as a component material in semiconductor, electronic, automobile, and mechanical fields.

For the growth of silicon carbide single crystals, for example, the Acheson method, in which carbon and silica are reacted in an electric furnace at a high temperature of 2000 degrees (℃) or higher, and the sublimation method, which uses silicon carbide as a raw material and sublimates it at a high temperature of 2000 degrees (℃) or higher to grow a single crystal. There are solution growth methods that apply the crystal pulling method. In addition, a method of chemical deposition using a gas source is being used.

However, it is very difficult to obtain high-purity silicon carbide single crystals with the Acheson method, and chemical vapor deposition may only allow growth to a limited level of thin film thickness. Accordingly, research has been focused on the sublimation method, which grows crystals by sublimating silicon carbide at high temperatures. However, the sublimation method is also generally performed at a high temperature of over 2400°C, and there is a high possibility of various defects such as micropipes and stacking defects occurring, so there is a limit in terms of production cost.

Therefore, there is active research on a solution growth method in which raw metals, including Si, are placed in a graphite crucible, the crucible is heated through induction heating to form a metal melt, and a SiC single crystal is grown on the seed crystal.

In the solution growth method for obtaining silicon carbide single crystals, the driving force for growing single crystals is the formation of supersaturation in the melt due to a temperature gradient. In other words, not only the temperature gradient but also where the high-temperature region and the low-temperature region are located in the melt are important for stable growth. In particular, if a hot spot or cold spot is formed at a specific location, it can accelerate silicon carbide polycrystal precipitation or corrosion of the crucible, making it difficult to obtain a single crystal of the desired shape. In addition, the lower part of the melt is maintained at a higher temperature than the upper part in order to precipitate single crystals from the seed crystals located on the surface of the melt, but in this case, there is a high risk that polycrystals will grow from the point where the surface of the melt and the inner wall of the crucible meet.

To solve this problem, conventionally, a graphite ring was mounted on the crucible to increase the temperature of the desired area.

On the other hand, induction heating performed in the solution growth method is a method of heating a conductor. When an eddy current flows through the object due to electromagnetic induction, Joule heat is generated, and the conductor is heated by this heat. am.

A flow is formed in the metal melt formed by the induction heating, and factors affecting this flow include interfacial force, electromagnetic force, centrifugal force, and buoyancy force. ). Among these, electromagnetic force has a great influence on forming the flow of melt.

Currently, in the solution growth method, the flow of melt formed under the seed is in two directions. However, the flow in the above two directions causes the surface quality of SiC single crystal to deteriorate.

Nevertheless, although the graphite ring installed to control the temperature gradient could increase the partial temperature, the flow direction was still bidirectional, making it difficult to improve the surface quality of the SiC single crystal.

Therefore, there is an urgent need for a method to solve this problem and create not only a temperature gradient but also a flow direction in one direction.

The present invention seeks to provide a device for manufacturing silicon carbide single crystals that provides a desirable flow direction and temperature distribution of metal melt to improve the quality of SiC single crystals.

In addition, the present invention provides a device for manufacturing a silicon carbide single crystal that can increase the SiC single crystal growth rate by increasing the mass transfer rate by controlling the flow direction of the metal melt.

Meanwhile, the technical problem to be solved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly apparent to those skilled in the art from the description below. It will be understandable.

An apparatus for manufacturing a silicon carbide single crystal according to an embodiment of the present invention includes a crucible including an outer peripheral surface,

an induction heating member surrounding the crucible, and

It includes a silicon carbide (SiC) seed crystal member provided inside the crucible,

The crucible includes a ring or discontinuous protrusion on the outer circumferential surface containing a material having greater electronic conductivity than the material forming the crucible.

The ring or discontinuous protrusion may comprise a material with an electronic conductivity exceeding 1E+5 S/m.

One or more discontinuous protrusions are formed on the outer peripheral surface of the crucible, and the total area occupied by the protrusions may be 2 to 40% of the total area of the outer surface forming the outer peripheral surface of the crucible.

The ring or discontinuous protrusion may be formed in a range of 30% to 70% of the height of the crucible.

The ring or discontinuous protrusion may be removable from the crucible.

Detachment of the ring or discontinuous protrusion and the crucible may be possible by mechanical means.

The thickness (T) of the ring or discontinuous protrusion may be 0.5t to 2t of the thickness (t) of the area in the crucible where the ring or discontinuous protrusion is formed.

The width (W) of the ring or discontinuous protrusion may be 1t to 7t of the crucible thickness (t) at the portion of the crucible where the ring or discontinuous protrusion is formed.

The crucible may be made of graphite.

The apparatus for manufacturing a silicon carbide single crystal may further include a rotating member that rotates the crucible.

The apparatus for manufacturing a silicon carbide single crystal may further include a reaction chamber containing the crucible.

The crucible may have a cylindrical outer circumference and a cup shape with an open top.

According to the device for manufacturing a silicon carbide single crystal according to the present invention, it is possible to improve the surface quality of the SiC single crystal by forming the flow of the melt below the seed in one direction in a very simple method, as well as to select an appropriate location. By adjusting the size of the flow, the temperature gradient within the melt can also be lowered, preventing metal mixing, and improving the quality of the single crystal.

In addition, the growth rate of SiC single crystals can also be increased by increasing the mass transfer rate by forming the flow of the melt below the seed upward.

1 is a schematic cross-sectional view of an apparatus for manufacturing a silicon carbide single crystal according to an embodiment;
2 and 3 are perspective views of a ring or discontinuous protrusion according to one embodiment;
Figure 4 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Example 1;
Figure 5 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Example 2;
Figure 6 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Example 3;
Figure 7 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Example 4;
Figure 8 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Example 5;
Figure 9 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Comparative Example 1;
Figure 10 is a simulation image of the temperature difference in the crucible and the flow of melt at the bottom of the seed for Comparative Example 2;
Figure 11 is a simulation image of the temperature difference within the crucible and the flow of melt at the bottom of the seed for Comparative Example 3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, in explaining this description, descriptions of already known functions or configurations will be omitted to make the gist of this description clear.

In order to clearly explain this description, parts that are not related to the description have been omitted, and identical or similar components are given the same reference numerals throughout the specification. In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, so this description is not necessarily limited to what is shown.

In the drawing, the thickness is enlarged to clearly express various layers and areas. Also, in the drawing, the thickness of some layers and regions is exaggerated for convenience of explanation. When a part of a layer, membrane, region, plate, etc. is said to be "on" or "on" another part, this includes not only being "directly above" the other part, but also cases where there is another part in between.

Figure 1 shows a schematic cross-sectional view of an apparatus for manufacturing a silicon carbide single crystal according to an embodiment.

Referring to FIG. 1, a silicon carbide single crystal manufacturing apparatus 100 according to an embodiment includes a crucible 110 including an outer peripheral surface, an induction heating type heating member 120 that surrounds and heats the crucible, and silicon carbide provided inside the crucible. It includes a seed crystal member 130.

Furthermore, the silicon carbide single crystal manufacturing apparatus 100 further includes a rotation member 140 that rotates the crucible 110 and a reaction chamber 150 containing the crucible 110.

Here, the crucible 110 is provided inside the reaction chamber 100 and may be in the shape of a cup with an open top, and the side of the cup shape forms the outer peripheral surface 111. However, without being limited to the above-mentioned form, any form in which the melt for forming a silicon carbide single crystal can be charged is possible, and a cover covering the upper surface may be included depending on the manufacturing process. In this crucible 110, a molten liquid (S) such as silicon or silicon carbide powder, or metal is charged and accommodated.

The crucible 110 may be made of a material containing carbon, such as graphite, graphite, or SiC. However, it is not limited thereto, and a crucible made of ceramic may be used. In this case, a material or source for providing carbon may be provided separately. You can. In detail, it may be made of graphite, which can be used as a source of carbon raw materials.

Meanwhile, the crucible 110 according to an embodiment of the present invention, unlike the prior art, may include a ring or discontinuous protrusion 112 on the outer peripheral surface 111 containing a material with greater conductivity than the material forming the crucible.

The ring or discontinuous protrusion 112 should have a different electronic conductivity than the crucible 110 and may comprise or be made of a material with a greater electronic conductivity. In one example, the ring or discontinuous protrusion 112 may include a material with an electronic conductivity greater than 1E+5 S/m, which is the electronic conductivity of graphite.

Otherwise, if it contains a material with the same electronic conductivity as that of the crucible 110, not only does the flow of the melt (S) generated in the lower part of the seed flow in two directions, but the temperature gradient cannot be lowered, which is a problem in which the quality of the single crystal deteriorates. Even if the electronic conductivity is different from that of the crucible 110, if it contains a smaller material, the temperature gradient may be lowered, but the flow of the melt S is still in two directions, which is not desirable.

Materials that satisfy the above conditions may be, for example, those listed in Table 1 below. Among these, considering that the melt is formed by heating the crucible to a high temperature, tungsten and molyb have a high melting point. Molybdenum and niobium are more preferable, and metals with somewhat low melting points satisfy the above conditions and can be used when manufactured as alloys. That is, the ring or discontinuous protrusion 112 includes one or more selected from the group consisting of tungsten, molybdenum, nickel, iron, platinum, niobium, carbon steel, titanium, and stainless steel. It can be made of one type, or it may be made of more than one type of alloy.

Electric conductivity Melting point Tungsten 1.8E+7 3422 Molybdenum 1.9E+7 2623 Nickel 1.4E+7 1455 Iron 1.0E+7 1538 Platinum 9.4E+6 1768 Niobium 7.0E+6 2477 Carbon steel 7.0E+6 1540 Titanium 2.4E+6 1668 Stainless steel 1.5E+6 1500

The ring or discontinuous protrusion 112 is coupled on the outer peripheral surface 111 of the crucible 110 and may be located at any height, but is at substantially the same level as the surface of the melt S located inside the crucible 110. It may be located at a height or a height lower than the surface of the melt (S). That is, it can be placed at any height overlapping with the melt (S) in order to change the temperature distribution of the melt (S). The height is approximately in the range of 30% to 70% in the height direction of the crucible.

In the case of discontinuous protrusions, the protrusions may all be formed at the same location.

The thickness (T) of the ring or discontinuous protrusion 112 means the protrusion height from the outer peripheral surface 111 of the crucible 110, and is the crucible thickness of the area where the ring or discontinuous protrusion 112 is formed in the crucible 110. Based on (t), it may be 0.5t to 2t.

Outside the above range, if the thickness T of the ring or discontinuous protrusion 112 is excessively large, effective heat transfer may be difficult, and if it is small, it is not sufficient to achieve the desired effect.

In addition, the width (W) of the ring or discontinuous protrusion means the length in the vertical direction of the thickness (T) in the vertical direction, and is the crucible thickness ( It may be 1t to 7t based on t), and in detail, it is more preferable to be 3t to 5t in terms of reducing the temperature gradient.

In fact, additional simulation results described below show that the width of the ring or discontinuous protrusion 112 appears to have a greater effect than the thickness. Additionally, the effect is as long as the ring or discontinuous protrusion is not too small.

Meanwhile, the ring or discontinuous protrusion 112 may be detachable from the outer peripheral surface 111 of the crucible 110, and the detachment may be possible through a mechanical method.

2 and 3 show this detachable type of ring or discontinuous protrusion 112.

Figure 2 is a perspective view of a ring according to one embodiment, and Figure 3 is a perspective view and a cross-sectional view of a discontinuous protrusion according to an embodiment.

First, referring to FIG. 2, the ring 112 surrounds the outer peripheral surface 111 of the crucible 110 in a shape having a constant width. However, the drawing is only an example, and the concept includes all structures with a certain width and a hollow interior.

Referring to FIG. 3, it may be a discontinuous protrusion 112 and is regularly formed on the outer peripheral surface 111 of the crucible 110. Specifically, one or more discontinuous protrusions 112 are formed, and the total area occupied by the protrusions may be 2 to 40% of the total area of the outer surface forming the outer peripheral surface of the crucible.

Meanwhile, the ring in FIG. 2 may include a screw thread-like shape at a portion in contact with the outer peripheral surface 111 of the crucible 110. Although not shown in the drawing, the outer surface of the outer peripheral surface 111 of the crucible 110 also has a ring. Alternatively, it may include corresponding threads for fastening to the inner threads of the discontinuous protrusion 112.

In addition, all of the discontinuous protrusions 112 in FIG. 3 may include protrusions or grooves at portions that contact the outer peripheral surface 111 of the crucible 110, and although not shown in the drawing, the outer peripheral surface 111 of the crucible 110 The outer surface may also include corresponding grooves or protrusions to be fastened to the protrusions or grooves of the discontinuous protrusion 112.

Accordingly, they may be mechanically removable structures.

In this drawing, a structure that is detachable by a mechanical method is shown, but in addition to a structure that is detachable by other methods, the ring or discontinuous protrusion 112 is completely attached to the outer peripheral surface 111 of the crucible 110 by welding, adhesion, etc. Of course, it can be a form.

Returning to FIG. 1 again, other members of the silicon carbide single crystal manufacturing apparatus 100 will be described.

The heating member 120 may heat the crucible 110 to melt or heat the material contained in the crucible 110. The heating member 120 may be positioned to be spaced apart from the outer peripheral surface 111 of the crucible 110. For example, the heating member 120 may have a shape that surrounds the outer peripheral surface 111 of the crucible 110 while being spaced apart.

This specification illustrates an embodiment in which the heating member 120 is located within the chamber 150, but the present invention is not limited thereto and the heating member 120 may be located outside the chamber 150.

The heating member 120 is an induction heating type heating member. Specifically, the heating member 120 includes an induction coil and flows a high-frequency current through the induction coil, thereby heating the crucible 110 by generating heat by eddy current. It's a method.

The silicon carbide seed crystal member 130 is a part where a silicon carbide single crystal is grown, and the seed crystal 131 located in the upper area inside the crucible 300 is in contact with the melt S or is in contact with the melt S. A seed crystal support member 133 that can move in the vertical direction and rotate the seed crystal 131, and a seed crystal shaft 132 that connects the seed crystal 131 and the seed crystal support member 133. Includes.

The lower surface of the seed crystal 131 may be positioned to contact the surface of the melt S located inside the crucible 110 depending on the manufacturing process.

The silicon carbide seed crystal 131 is made of a silicon carbide single crystal. The crystal structure of the silicon carbide seed crystal 131 is the same as that of the silicon carbide single crystal to be manufactured. For example, when manufacturing a 4H polytype silicon carbide single crystal, the 4H polytype silicon carbide seed crystal 131 can be used. When using the 4H polymorph silicon carbide seed crystal 131, the crystal growth plane is the (0001) plane or (000-1) plane, or is tilted at an angle of 8 degrees or less from the (0001) plane or (000-1) plane. It could be a photo plane.

The seed crystal shaft 132 is extended to connect to the upper surface of the silicon carbide seed crystal 131, supports the silicon carbide seed crystal 131, and allows the silicon carbide seed crystal 131 to be located inside the crucible 110. do.

The seed crystal shaft 132 may be coupled to the seed crystal rotating rod 133 to rotate together, and the seed crystal shaft 132 may move or rotate up and down by the seed crystal rotating rod 133.

The rotation member 140 may be coupled to the lower side of the crucible 110 to rotate the crucible 110. By rotating the crucible 110, it is possible to provide a melt (S) of uniform composition, so a high-quality silicon carbide single crystal can be grown on the silicon carbide seed crystal 131.

The reaction chamber 150 is in a sealed form including an empty internal space. The interior of the reaction chamber 150 may be maintained in an atmosphere such as constant pressure. Although not shown, a vacuum pump and a gas tank for atmosphere control may be connected to the reaction chamber 150. The inside of the reaction chamber 150 can be made into a vacuum state using a vacuum pump and an atmosphere control gas tank, and then filled with an inert gas such as argon gas.

Hereinafter, with reference to FIGS. 4 to 11, the temperature difference within the crucible and the melt flow at the bottom of the seed according to Examples and Comparative Examples will be examined. Figures 4 to 8 are simulation images of the temperature difference and melt flow for Examples 1 to 5, and Figures 9 to 11 are simulation images of the temperature difference and melt flow for Comparative Examples 1 to 3.

The electronic conductivity of the materials used below is disclosed in previously disclosed literature.

First, Figure 4 shows a case where a ring made of tungsten (when the crucible wall thickness is t, thickness: t, width: 3t) is attached to the crucible according to Example 1, and the electronic conductivity is about 1.8E+7. and is greater than the electronic conductivity of a crucible made of graphite.

Referring to FIG. 4, the temperature gradient was lowered by the metal ring, and the temperature difference (△T) between the highest temperature and the lowest temperature was 1.95°C, and it was confirmed that the melt flow at the bottom of the seed was in one direction.

Next, Figures 5 to 8 show a case where a ring made of tungsten was attached in the same manner as in Example 1, but the thickness and width were different.

Figure 5 shows a tungsten ring with a thickness of 0.5t and a width of t, Figure 6 shows a tungsten ring with a thickness of 0.5t and a width of 5t, and Figure 7 shows a ring with a thickness of 1.5t and a width of 5t. Figure 8 shows a tungsten ring with a thickness of 1.5t and a width of t attached.

Referring to Figures 5 to 8, the melt flow at the bottom of the seed is in one direction. However, there is a certain difference in the temperature gradient, and from this, it can be confirmed that there is a difference in the temperature gradient depending on the thickness and width of the ring. In the case of Figure 5, the temperature difference (△T) between the highest temperature and the lowest temperature is 2.886°C, in the case of Figure 6, the temperature difference (△T) between the highest temperature and the lowest temperature is 1.61°C, and in the case of Figure 7, the highest temperature - the lowest temperature The temperature difference (△T) is 1.522°C, and in the case of Figure 8, the temperature difference (△T) between the highest temperature and the lowest temperature is 2.439°C.

From this, it can be seen that the width of the ring or protrusion is more important in lowering the temperature gradient, and is more desirable when it is 3t to 5t.

Next, Figure 9 shows a case where a ring made of Cu-Fe alloy or clay (when the crucible wall thickness is t, thickness: t, width: 3t) was used according to Comparative Example 1, and the electronic conductivity was about 1E. +3 S/m, which is smaller than the electronic conductivity of a crucible made of graphite.

Referring to FIG. 9, the temperature gradient can be lowered to a certain extent by the metal ring (ΔT = 3.94°C), but it can be seen that the melt flow at the bottom of the seed is still in two directions.

Figure 10 shows the case of using a graphite ring (thickness: t, width: 3t, when the crucible wall thickness is t) according to Comparative Example 2, the electronic conductivity is 1E+5 S/m, and the electronic conductivity of the crucible is same.

Referring to FIG. 10, compared to Comparative Example 3 below where a ring is not attached to the outer peripheral surface of the crucible, the temperature gradient can be lowered to a certain extent (△T = 4.86°C), but there is still a large temperature difference, and the temperature gradient at the bottom of the seed is still large. It can be seen that the melt flow is still in two directions.

Figure 11 shows a case in which no ring or wire of any kind is mounted on the outer peripheral surface of the crucible, according to Comparative Example 3.

Referring to Figure 11, it can be seen that the temperature gradient cannot be lowered, the temperature difference is significant (△T = 4.92°C), and the melt flow in the lower part of the seed is in two directions.

Although specific embodiments of the present invention have been described and shown above, it is known in the art that the present invention is not limited to the described embodiments, and that various modifications and changes can be made without departing from the spirit and scope of the present invention. This is self-evident to those who have it. Accordingly, such modifications or variations should not be understood individually from the technical idea or viewpoint of the present invention, and the modified embodiments should be regarded as falling within the scope of the claims of the present invention.

Claims (12)

A crucible comprising an outer circumferential surface,
an induction heating member surrounding the crucible, and
It includes a silicon carbide (SiC) seed crystal member provided inside the crucible,
The crucible includes a discontinuous protrusion on the outer circumferential surface comprising a material having an electronic conductivity greater than 1E+5 S/m than the material forming the crucible,
The crucible is made of graphite,
An apparatus for manufacturing a silicon carbide single crystal, wherein one or more discontinuous protrusions are formed, and all of the discontinuous protrusions are formed at the same position based on the height direction of the crucible. delete The apparatus for manufacturing a silicon carbide single crystal according to claim 1, wherein the discontinuous protrusion has a total area of 2 to 40% of the total area of the outer surface forming the outer peripheral surface of the crucible. According to paragraph 1,
A device for manufacturing a silicon carbide single crystal, wherein the discontinuous protrusion is formed in a range of 30% to 70% in the height direction of the crucible. According to paragraph 1,
The discontinuous protrusion is a device for manufacturing a silicon carbide single crystal that is detachable from the crucible. According to clause 5,
A device for manufacturing a silicon carbide single crystal in which the discontinuous protrusion and the crucible can be detached by a mechanical method. According to paragraph 1,
The thickness (T) of the discontinuous protrusion is 0.5t to 2t of the thickness (t) of the portion in the crucible where the discontinuous protrusion is formed. According to paragraph 1,
The width (W) of the discontinuous protrusion is 1t to 7t of the crucible thickness (t) at the portion where the discontinuous protrusion 112 is formed in the crucible. delete According to paragraph 1,
The apparatus for manufacturing a silicon carbide single crystal further includes a rotating member that rotates the crucible. According to paragraph 1,
The apparatus for manufacturing a silicon carbide single crystal further includes a reaction chamber containing the crucible. The apparatus for manufacturing a silicon carbide single crystal according to claim 1, wherein the crucible has a cylindrical outer peripheral surface and a cup shape with an open upper surface.

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