Single crystal growth furnace

Abstract

The utility model discloses a single crystal growth furnace, the single crystal growth furnace comprises a furnace body and a heating mechanism, the furnace body encloses to form a furnace chamber; the heating mechanism is located in the furnace cavity and comprises a lower heater, a side heater and an upper heater assembly, and the lower heater, the side heater and the upper heater assembly define a heating cavity used for containing a heating container and heating raw materials. The upper heater assembly comprises an inner heater and an outer heater which are independently arranged. According to the single crystal growth furnace provided by the invention, through the combined action of the inner heater and the outer heater, the temperature of each part of the crystal growth region is uniform, the temperature difference between the middle position and the edge position of the crystal growth region is reduced, and the radial temperature gradient of the crystal growth region is reduced, so that the stress of growing crystals is reduced; crystal cracking is avoided, and the uniformity of the resistivity of the crystal wafer is improved.

Description

Technical Field

[0001] This application relates to the field of crystal preparation, and more particularly to a single crystal growth furnace. Background Technology

[0002] The mainstream method for preparing silicon carbide single crystals is the physical vapor transport (PVT) method. In PVT, a graphite crucible is used within a medium-frequency induction heating coil. Due to the skin effect, magnetically induced eddy currents are mainly concentrated on the surface of the crucible, generating resistance heat that raises the temperature of the graphite crucible. The temperature is then transferred to the powder and seed crystal inside the crucible through heat conduction, radiation, and convection, gradually increasing their temperature as well.

[0003] Since the medium-frequency induction heating method uses the crucible wall as the heat source, the heating method of growing silicon carbide single crystals by physical vapor transport will result in an excessive radial temperature gradient inside the crucible. An excessive radial temperature gradient is not conducive to crystal growth, resulting in large thermal stress in the grown single crystal, which often makes the crystal prone to cracking. Utility Model Content

[0004] To address the aforementioned problems, the purpose of this application is to provide a single crystal growth furnace that can reduce the stress on the grown crystal and prevent crystal cracking.

[0005] To achieve the above objectives, this application provides a single crystal growth furnace, which includes a furnace body and a heating mechanism. The furnace body encloses a furnace cavity. The heating mechanism is located inside the furnace cavity and includes a lower heater, a side heater, and an upper heater assembly. The lower heater, side heater, and upper heater assembly enclose a heating cavity for accommodating a heating container and heating the raw material. The upper heater assembly includes an independently disposed inner heater and an outer heater.

[0006] Define a preset plane perpendicular to the axis of the furnace cavity. The orthographic projection of the inner heater in the preset plane is the inner projection, and the orthographic projection of the outer heater in the preset plane is the outer projection. The inner projection is located inside the outer projection.

[0007] Furthermore, the outer heater is configured as an annular shape, and the ratio of the outer diameter of the outer heater to the inner diameter of the side heater ranges from 0.8 to 1.1, while the ratio of the inner diameter of the outer heater to the inner diameter of the side heater ranges from 0.5 to 0.8.

[0008] Furthermore, the inner heater is configured as an annular shape, and the ratio of the outer diameter of the inner heater to the inner diameter of the side heater ranges from 0.3 to 0.6, while the ratio of the inner diameter of the inner heater to the inner diameter of the side heater ranges from 0.1 to 0.3.

[0009] Furthermore, the inner heater is set at the same height as the outer heater, and the inner heater is located inside the outer heater.

[0010] Furthermore, a preset plane is defined that is perpendicular to the axis of the furnace cavity. The orthographic projection of the inner heater in the preset plane is the inner projection, and the orthographic projection of the outer heater in the preset plane is the outer projection. The overlapping area of ​​the inner projection and the outer projection is 0.

[0011] Furthermore, the power of the internal heater is greater than or equal to the power of the external heater.

[0012] Furthermore, the external heater is positioned higher than the internal heater.

[0013] Furthermore, at least one of the internal heater or the external heater is configured to be movable along the axis of the furnace cavity.

[0014] Furthermore, at least one of the inner heater or the outer heater is a graphite heating ring.

[0015] Furthermore, an upper temperature measuring channel extending along the axis of the furnace cavity is formed at the top of the furnace body, and a lower temperature measuring channel extending along the axis of the furnace cavity is formed at the bottom of the furnace body.

[0016] In summary, the single crystal growth furnace provided in this application is equipped with an upper heater assembly including an inner heater and an outer heater. The combined action of the inner heater and the outer heater makes the temperature uniform throughout the crystal growth region, reduces the temperature difference between the middle and edge positions of the crystal growth region, reduces the radial temperature gradient of the crystal growth region, thereby reducing the stress on the grown crystal, avoiding crystal cracking, and improving the uniformity of the resistivity of the crystal wafer. Attached Figure Description

[0017] Figure 1 This is a three-dimensional schematic diagram of the single crystal growth furnace provided in this application;

[0018] Figure 2 This is a structural cross-sectional schematic diagram of the single crystal growth furnace provided in this application;

[0019] Figure 3 This is a schematic cross-sectional view of the structure of the single crystal growth furnace provided in this application, showing that the outer heater is positioned higher than the inner heater.

[0020] Figure 4 This is a schematic cross-sectional view of the structure of a single crystal growth furnace provided in this application, in which the external heater is configured to move along the furnace cavity axis.

[0021] Figure 5 This is a top view of the upper heater assembly in the single crystal growth furnace provided in this application;

[0022] Figure 6 This is a schematic diagram of the dimensions of the upper heater assembly and the side heater in the single crystal growth furnace provided in this application;

[0023] Figure 7This is a schematic diagram of the stress distribution of wafers obtained by existing single crystal growth furnaces;

[0024] Figure 8 This is a schematic diagram of the stress distribution of a wafer prepared using a single crystal growth furnace according to the present application;

[0025] In the figure: 100, Single crystal growth furnace; 11, Furnace body; 111, Furnace cavity; 112, Upper temperature measuring channel; 113, Lower temperature measuring channel; 12, Heating mechanism; 121, Lower heater; 122, Side heater; 123, Upper heater assembly; 1231, Inner heater; 1232, Outer heater; 1233, Adjustment component; 124, Heating chamber; 101, First straight line; 102, Preset plane; 200, Heating container. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, this application provides a single crystal growth furnace 100, including a furnace body 11 and a heating mechanism 12. The furnace body 11 encloses a furnace cavity 111, and may be made of heat-insulating material to prevent heat loss. The heating mechanism 12 is located within the furnace cavity 111 and includes a lower heater 121, a side heater 122, and an upper heater assembly 123, which together form a heating chamber 124. The lower heater 121 is located at the bottom of the furnace cavity 111 and is used to heat the bottom region of the heating chamber 124; specifically, the lower heater 121 is mainly used to heat the raw materials. The side heater 122 is disposed against the inner wall of the furnace cavity 111 and has an annular structure extending along a first straight line 101. One end of the side heater 122 extends upward along the first straight line 101 to a position near the upper heater assembly 123, and the other end of the side heater 122 extends downward along the first straight line 101 to a position near the lower heater 121. Specifically, the upper edge of the side heater 122 is near the bottom of the upper heater assembly 123, and the lower edge of the side heater 122 is near the top of the lower heater 121. The upper heater assembly 123 is located at the top of the furnace cavity 111 and is mainly used to heat the crystal growth region. The heating cavity 124 is used to house the heating container and heat the raw material. The raw material is heated in the heating cavity 124 and grows into a single crystal, which grows in the top region of the heating cavity 124. For ease of explanation, the region where the single crystal grows is referred to as the crystal growth region. A first straight line 101 parallel to the extension direction of the furnace body 11 is defined, and the first straight line 101 is parallel to the axis of the furnace cavity 111.

[0028] In this embodiment, the upper heater assembly 123 includes an inner heater 1231 and an outer heater 1232, which are independently configured. A preset plane 102 is defined perpendicular to the axis of the furnace cavity 111. The orthographic projection of the inner heater 1231 onto the preset plane 102 is the inner projection, and the orthographic projection of the outer heater 1232 onto the preset plane 102 is the outer projection. The inner heater 1231 and outer heater 1232 are independently configured, and viewed from the axial direction of the furnace cavity 111, the inner heater 1231 is substantially located inside the outer heater 1232, and the outer heater 1232 is substantially located outside the inner heater 1231. The outer heater 1232 is used to heat the edge of the crystal growth region, and the inner heater 1231 is used to heat the middle of the crystal growth region. This avoids low temperatures in the middle of the crystal growth region, ensuring uniform heating of the crystal growth region, reducing the radial temperature gradient of the crystal growth region, and improving the uniformity of the crystal wafer resistivity. The inner heater 1231 and the outer heater 1232 are independent heating devices. The power settings of the inner heater 1231 and the outer heater 1232 do not affect each other, and the inner heater 1231 and the outer heater 1232 can be adjusted independently to meet different heating needs.

[0029] Based on the above description, the single crystal growth furnace 100 provided in this application includes an upper heater assembly 123 comprising an inner heater 1231 and an outer heater 1232 within the furnace body 11. This improves the freedom of heating control within the furnace body. In actual production, the inner heater 1231 is controlled to heat the central position of the crystal growth region, increasing the temperature at the central position and preventing low temperatures in the central position. The combined action of the inner heater 1231 and the outer heater 1232 ensures uniform temperature throughout the crystal growth region, reducing the temperature difference between the central and edge positions, lowering the radial temperature gradient of the crystal growth region, thereby reducing stress on the grown crystal, preventing crystal cracking, and improving the uniformity of the crystal wafer resistivity.

[0030] For clearer illustration, the heating container 200 is also shown in the accompanying drawings. The heating container 200 can specifically be configured as a crucible or other heating container. The heating container 200 is used to hold the crystal growth raw materials, and its top also provides a growth interface for crystal growth. The top of the heating container 200 corresponds substantially to the aforementioned crystal growth region. It should be noted that although the heating container 200 is included in the description of this application, this is only for clearer illustration of the single crystal growth furnace 100 provided in this application; the heating container 200 is not part of the single crystal growth furnace 100.

[0031] As one implementation method, at least one of the inner heater 1231 or the outer heater 1232 is a graphite heating ring. Graphite material has characteristics such as high thermal conductivity, high temperature resistance and chemical stability. In the single crystal growth furnace 100, the inner heater 1231 or the outer heater 1232 is made of graphite material, which can improve the heating uniformity, avoid the damage to the crystal structure caused by local overheating, and also reduce the risk of metal contamination, ensuring a clean crystal growth environment.

[0032] As one implementation method, such as Figure 2 As shown, an upper temperature measuring channel 112 extending along the axis of the furnace cavity 111 is formed at the top of the furnace body 11. That is, the top of the furnace body 11 has an opening that extends along the direction of the first straight line 101 to form the upper temperature measuring channel 112. The temperature measuring element measures the temperature of the area at the top of the furnace body 11 through the upper temperature measuring channel 112, mainly measuring the temperature of the crystal growth area. A lower temperature measuring channel 113 extending along the axis of the furnace cavity 111 is formed at the bottom of the furnace body 11. That is, the bottom of the furnace body 11 also has an opening that extends along the direction of the first straight line 101 to form the lower temperature measuring channel 113. The temperature measuring element measures the temperature of the area at the bottom of the furnace body 11 through the lower temperature measuring channel 113, mainly measuring the temperature of the raw materials. Optionally, the openings of the upper temperature measuring channel 112 and the lower temperature measuring channel 113 can be located at the center of the top and bottom of the furnace body 11, or at other locations at the top and bottom of the furnace body 11.

[0033] As one implementation method, such as Figure 2 As shown, the inner heater 1231 and the outer heater 1232 can be set at approximately the same height, with the inner heater 1231 located inside the outer heater 1232. The outer heater 1232 is located outside the inner heater 1231, and heats the edge of the crystal growth region by heating the outer portion of the top of the heating container 200. The inner heater 1231 heats the middle portion of the top of the heating container 200, thus preventing low temperatures in the middle of the crystal growth region. The combined heating of the crystal growth region by the inner heater 1231 and the outer heater 1232 ensures uniform temperature throughout the crystal growth region, reduces the temperature difference between the middle and edge positions, lowers the radial temperature gradient, and improves the uniformity of the crystal wafer resistivity.

[0034] As one implementation method, such as Figure 2As shown, a preset plane 102 is defined perpendicular to the axis of the furnace cavity 111. The orthographic projection of the inner heater 1231 in the preset plane 102 is the inner projection, and the orthographic projection of the outer heater 1232 in the preset plane 102 is the outer projection. The overlapping area of ​​the inner and outer projections is 0. The inner heater 1231 and the outer heater 1232 do not overlap. The inner heater 1231 and the outer heater 1232 are independently set in the top area of ​​the heating container 200. The operating status of the inner heater 1231 and the outer heater 1232 can be independently adjusted. In particular, the power of the heater 1241 and the outer heater 1232 can be independently adjusted to meet different heating needs.

[0035] As one implementation, the power of the inner heater 1231 is configured to be greater than or equal to the power of the outer heater 1232. This is used to raise the temperature at the top center of the heating container 200, thereby raising the temperature at the center of the crystal growth region. This causes the crystal growth region to bulge slightly, resulting in an ideal crystal growth interface. This allows for control over the crystal growth interface, solving the problem of difficulty in controlling the growth cross-section of large-sized crystals such as 8-inch, 10-inch, and 12-inch crystals. Optionally, the heating power of the outer heater 1232 can also be reduced, thereby lowering the temperature at the top edge of the heating container 200. This also causes the crystal growth region to bulge slightly, achieving control over the crystal growth cross-section.

[0036] As one implementation method, such as Figure 3 As shown, the external heater 1232 can be configured to be higher than the internal heater 1231. The distance from the external heater 1232 to the top region of the heating container 200 is greater than the distance from the internal heater 1231 to the top region of the heating container 200. By increasing the distance from the external heater 1232 to the crystal growth region, the heat applied to the crystal growth region by the external heater 1232 is reduced; or by decreasing the distance from the internal heater 1231 to the crystal growth region, the heat applied to the crystal growth region by the internal heater 1231 is increased. This increases the temperature at the middle position of the top of the heating container 200, causing the crystal growth region to convex slightly, obtaining an ideal crystal growth interface, and achieving control over the crystal growth cross section.

[0037] As one implementation method, such as Figure 4As shown, at least one of the inner heater 1231 or the outer heater 1232 is configured to be movable along the axis of the furnace cavity 111. Taking the outer heater 1232 as an example, an adjusting member 1243 is provided connected to the outer heater 1232, and the distance between the outer heater 1232 and the top of the heating container 200 is adjusted by the adjusting member 1243. As the crystal continues to grow, the crystal thickens, and the growing crystal gradually extends to the bottom of the furnace cavity 111 along the direction of the first straight line 101. At this time, the radial gradient and axial gradient of the crystal continuously change with the crystal growth. The inner heater 1231 or the outer heater 1232 is moved by the adjusting member 1243 to heat the crystal. Optionally, an adjusting member 1243 connected to the inner heater 1231 can also be provided to adjust the position of the inner heater 1231 for heating the crystal. In addition, adjusting members can be connected to both the outer heater 1232 and the inner heater 1231 simultaneously, giving both the outer heater 1232 and the inner heater 1231 adjustment freedom.

[0038] As one implementation method, such as Figure 5 As shown, the external heater 1232 is configured as a ring to uniformly heat the crystal growth region. Figure 6 As shown, the ratio of the outer diameter L1 of the external heater 1232 to the inner diameter L5 of the side heater 122 ranges from 0.8 to 1.1, and the ratio of the inner diameter L2 of the external heater 1232 to the inner diameter L5 of the side heater 122 ranges from 0.5 to 0.8. The external heater 1232 can basically cover the edge of the top of the heating container 200, thereby uniformly heating the edge of the crystal growth region, making the temperature uniform throughout the crystal growth region and reducing the radial temperature gradient of the crystal growth region. Within the above range, it can avoid heat overflow and energy waste caused by the external heater 1232 being too large, and it can also avoid the existence of heating blind spots at the edge of the crystal growth region caused by the external heater 1232 being too small, ensuring that the thermal field at the edge of the heating container 200 and the crystal growth region form effective thermal coupling. The ratio of the inner diameter L2 of the external heater 1232 to the inner diameter L5 of the side heater 122 is within the above range. This can avoid thermal interference to the middle position of the crystal growth region caused by the inner diameter L2 of the external heater 1232 being too large, avoid the overlap of the thermal fields of the external heater 1232 and the internal heater 1231, and also avoid abrupt changes in the radial temperature gradient caused by the inner diameter L2 of the external heater 1232 being too small.

[0039] As one implementation method, such as Figure 5 As shown, the internal heater 1231 is configured as a ring to uniformly heat the crystal growth region. Figure 6As shown, the ratio of the outer diameter L3 of the inner heater 1231 to the inner diameter L5 of the side heater 122 ranges from 0.3 to 0.6, and the ratio of the inner diameter L4 of the inner heater 1231 to the inner diameter L5 of the side heater 122 ranges from 0.1 to 0.3. The heating range of the inner heater 1231 can basically cover the middle position of the top of the heating container 200. The inner heater 1231 uniformly heats the middle position of the crystal growth region through the top of the heating container 200, increasing the temperature of the middle position of the crystal growth region and avoiding low temperature in the middle position of the crystal growth region, thereby reducing the temperature difference between the middle position and the edge position of the crystal growth region. Within the above range, it can avoid the overlap of the thermal field of the inner heater 1231 with the outer heater 1242 due to the inner heater 1231 being too large, and avoid insufficient heating of the heating container 200 by the inner heater 1231; it can also avoid insufficient heating of the middle position of the crystal growth region due to the inner heater 1231 being too small. The ratio of the inner diameter L4 of the inner heater 1231 to the inner diameter L5 of the side heater 122 is within the above range. This can avoid the lack of heating in the central region of the crystal growth area due to the inner diameter L4 of the inner heater 1231 being too large, and can also avoid the radial heat accumulation phenomenon in the middle position of the crystal growth area due to the inner diameter L4 of the inner heater 1231 being too small.

[0040] The stress distribution of crystal wafers produced by existing equipment (i.e., single crystal growth furnaces without the upper heating component 123 described in this application) is as follows: Figure 7 As shown, in existing crystal preparation methods, a significant radial temperature gradient exists in the crystal growth region. This large radial temperature gradient leads to substantial thermal stress in the grown single crystal, making it prone to cracking. The stress distribution of the crystal wafer obtained by the single crystal growth furnace 100 provided in this application is shown in the figure. Figure 8 As shown, by uniformly heating the crystal growth region, the radial temperature gradient of the crystal growth region is reduced, thereby reducing the thermal stress inside the grown crystal and preventing crystal cracking.

[0041] Based on the above description, the single crystal growth furnace 100 provided in this application includes an upper heater assembly 123 comprising an inner heater 1231 and an outer heater 1232 within the furnace body 11, thereby increasing the freedom of heating control within the furnace body. In actual production, the inner heater 1231 is controlled to heat the central position of the crystal growth region, preventing low temperatures in the central position. The combined action of the inner heater 1231 and the outer heater 1232 ensures uniform temperature throughout the crystal growth region, reducing the temperature difference between the central and edge positions, lowering the radial temperature gradient, reducing stress on the grown crystal, preventing crystal cracking, and improving the uniformity of crystal wafer resistivity. Furthermore, the heating power of the inner heater 1231 and the outer heater 1232 can be controlled separately to obtain crystal growth cross-sections with different states such as convex, flat, and concave, thereby achieving control over the growth cross-section of large-size crystals.

[0042] Finally, it should be noted that the above are only some preferred embodiments of this application and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A single crystal growth furnace (100), characterized in that, include: Furnace body (11), the furnace body enclosing to form furnace cavity (111); as well as A heating mechanism (12) is located inside the furnace cavity (111). The heating mechanism (12) includes a lower heater (121), a side heater (122), and an upper heater assembly (123). The lower heater (121), the side heater (122), and the upper heater assembly (123) enclose a heating cavity (124) for accommodating a heating container and heating raw materials. The upper heater assembly (123) includes an independently configured inner heater (1231) and an outer heater (1232). Define a preset plane (102) perpendicular to the axis of the furnace cavity (111). The orthographic projection of the inner heater (1231) in the preset plane (102) is the inner projection, and the orthographic projection of the outer heater (1232) in the preset plane (102) is the outer projection. The inner projection is located inside the outer projection.

2. The single crystal growth furnace (100) according to claim 1, characterized in that: The outer heater (1232) is configured as an annular shape, and the ratio of the outer diameter of the outer heater (1232) to the inner diameter of the side heater is in the range of 0.8 to 1.1, and the ratio of the inner diameter of the outer heater (1232) to the inner diameter of the side heater is in the range of 0.5 to 0.

8.

3. The single crystal growth furnace (100) according to claim 1, characterized in that: The inner heater (1231) is configured as an annular shape, and the ratio of the outer diameter of the inner heater (1231) to the inner diameter of the side heater is in the range of 0.3 to 0.6, and the ratio of the inner diameter of the inner heater (1231) to the inner diameter of the side heater is in the range of 0.1 to 0.

3.

4. The single crystal growth furnace (100) according to claim 1, characterized in that: The inner heater (1231) is set at the same height as the outer heater (1232), and the inner heater (1231) is located inside the outer heater (1232).

5. The single crystal growth furnace (100) according to claim 4, characterized in that: The overlapping area of ​​the inner projection and the outer projection is 0.

6. The single crystal growth furnace (100) according to claim 4, characterized in that: The power of the inner heater (1231) is greater than or equal to the power of the outer heater (1232).

7. The single crystal growth furnace (100) according to claim 1, characterized in that: The external heater (1232) is positioned higher than the internal heater (1231).

8. The single crystal growth furnace (100) according to claim 1, characterized in that: At least one of the inner heater (1231) or the outer heater (1232) is configured to be movable along the axis of the furnace cavity (111).

9. The single crystal growth furnace (100) according to claim 1, characterized in that: At least one of the inner heater (1231) or the outer heater (1232) is a graphite heating ring.

10. The single crystal growth furnace (100) according to claim 1, characterized in that: The top of the furnace body forms an upper temperature measuring channel (112) extending along the axis of the furnace cavity (111), and the bottom of the furnace body forms a lower temperature measuring channel (113) extending along the axis of the furnace cavity (111).

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