A silicon molten liquid level detection device and a single crystal furnace

Abstract

The present invention provides a detection device for the position of the silicon melt surface and a single crystal furnace, the detection device comprising: a double-headed hook, the double-headed hook is located on the inner side of the combined sleeve, the upper end of the double-headed hook is fixedly connected to the side wall of the combined sleeve, the lower end of the double-headed hook extends downward from the bottom of the combined sleeve, and is used to form a reflection on the silicon melt surface; a detection unit, the detection unit is used to capture the reflection image formed by the lower end of the double-headed hook on the silicon melt surface. According to the detection device of the embodiment of the present invention, by using the double-headed hook to form a stable and clear reflection on the silicon melt surface, the detection unit can accurately capture the reflection and then measure the exact position of the silicon melt surface, thereby ensuring the accuracy of the adjustment of various parameters in the crystal pulling process and improving the quality of the obtained crystal rod.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal preparation, and in particular to a device for detecting the liquid level position of a silicon melt and a single crystal furnace. Background Art

[0002] With the continuous improvement of the process of the microelectronics industry, higher requirements are placed on the quality of silicon wafer materials. Good quality means controlling the crystal defects in the crystal rod. The generation of these defects is related to the axial temperature difference G of the crystal rod, and the axial temperature difference G can be adjusted according to the design of the hot zone and process optimization. The combined sleeve design can adjust the crystal rod G and ΔG (the difference between the axial temperature difference at the edge of the crystal rod and the axial temperature difference at the center of the crystal rod), adjust the stability of the solid-liquid-gas three-phase junction of the silicon melt, and adjust the smoothness of the argon flow in the furnace, which is beneficial to the defect-free growth of the crystal rod. On the other hand, some important parameters in the crystal pulling process can be optimized and processed precisely. One of the important parameters is the melt gap, which is the distance between the silicon melt liquid level and the bottom of the guide tube. The measurement and control of the melt gap is an important parameter indicator in the crystal pulling process. The melt gap should be measured after the material is quenched, and the melt gap should be adjusted to the set value by adjusting the liquid level position. In the subsequent crystal rod pulling process, the melt will continue to decrease during the pulling process, and the liquid level will continue to drop. At the same time, the crucible must continue to rise, which requires the melt gap to be monitored in real time and accurately adjusted. However, in the prior art, the detection accuracy of the silicon melt liquid level position is low, which cannot meet the needs of high-precision adjustment of crystal pulling process parameters, and the quality of the silicon wafer material finally prepared cannot meet the increasingly high requirements of the current market. Summary of the invention

[0003] In view of this, the present invention provides a silicon melt liquid level detection device and a single crystal furnace, which can solve the problem that the silicon melt liquid level detection accuracy in the prior art is low and cannot meet the control requirements of the high-quality silicon rod preparation process.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] In one aspect, an embodiment of the present invention provides a device for detecting the liquid level of a silicon melt, which is applied to a single crystal furnace. The single crystal furnace includes a crucible, a guide tube and a combined sleeve located directly above the crucible, and the combined sleeve is arranged at an opening of the inner bottom of the guide tube. The detection device includes:

[0006] A double-ended hook, wherein the double-ended hook is located on the inner side of the combined sleeve, the upper end of the double-ended hook is fixedly connected to the side wall of the combined sleeve, and the lower end of the double-ended hook extends downward from the bottom of the combined sleeve to form a reflection on the surface of the silicon melt;

[0007] A detection unit is used to capture the reflection image formed by the lower end of the double-headed hook on the surface of the silicon melt.

[0008] Optionally, the double-headed hook includes a plug connector, a connecting rod and an imaging body, the two ends of the connecting rod are respectively connected to the plug connector and the imaging body, the plug connector is inserted and fixed in the side wall of the combination sleeve, the imaging body includes a first contact head and a second contact head, and the horizontal distance between the first contact head and the axis of the combination sleeve is greater than the horizontal distance between the second contact head and the axis of the combination sleeve.

[0009] Optionally, the longitudinal cross-section of the plug connector is triangular or polygonal, and the side wall of the combined sleeve is provided with a plug hole that matches the shape of the plug connector.

[0010] Optionally, the detection unit is a CCD camera.

[0011] Optionally, the distance between the bottom of the first contact head and the surface of the molten silicon is greater than the distance between the bottom of the second contact head and the surface of the molten silicon.

[0012] Optionally, the first contact head and the second contact head are formed as cylinders, the imaging body further comprises a connecting block, the connecting block is fixedly connected to the connecting rod, the upper end of the first contact head is fixedly connected to the bottom surface of the connecting block, and the bottom surface of the connecting block is formed into a polygon.

[0013] Optionally, the connecting rod and the second contact head are an integral structure.

[0014] Optionally, the combined sleeve includes an inner tube, an outer tube and a thermal insulation layer, the outer tube is sleeved on the outer periphery of the inner tube, the thermal insulation layer is arranged between the inner tube and the outer tube, a plurality of heat-conducting holes are evenly distributed on the side wall of the thermal insulation layer, a plurality of annular grooves are formed on the outer peripheral surface of the outer tube, and the plurality of annular grooves are arranged at intervals along the axial direction of the outer tube.

[0015] Optionally, the inner cylinder is made of graphite material, and the thermal insulation layer is made of carbon fiber thermal insulation felt.

[0016] Another embodiment of the present invention further provides a single crystal furnace, which includes a crucible and a guide tube and a combined sleeve located directly above the crucible, wherein the combined sleeve is arranged at the opening of the inner bottom of the guide tube, and also includes a silicon melt liquid level position detection device as described in any of the above items.

[0017] The beneficial effects of the above technical solution of the present invention are as follows:

[0018] According to the detection device of the embodiment of the present invention, a double-headed hook is used to form a stable and clear reflection on the surface of the silicon melt, so that the detection unit can accurately capture the reflection and then measure the exact position of the silicon melt surface, thereby ensuring the accuracy of the adjustment of various parameters in the crystal pulling process and improving the quality of the obtained crystal rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a single crystal furnace provided in an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a detection device provided by an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of a double-ended lifting hook provided in an embodiment of the present invention;

[0022] Figure 4 Schematic diagram of the structure of the inner cylinder in an embodiment of the present invention;

[0023] Figure 5 is a schematic cross-sectional view of an inner cylinder in an embodiment of the present invention;

[0024] Figure 6 is a schematic diagram of a heat insulation layer in an embodiment of the present invention;

[0025] Figure 7 is a schematic diagram of an outer cylinder in an embodiment of the present invention;

[0026] Figure 8 for Figure 7 Enlarged schematic diagram of part A. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0028] Please refer to Figure 1 , is a schematic diagram of a single crystal furnace provided in an embodiment of the present invention. Figure 1As shown, an embodiment of the present invention provides a device for detecting the liquid level position of molten silicon, which is applied to a single crystal furnace. The single crystal furnace includes a crucible and a guide tube 1 and a combined sleeve 2 located directly above the crucible, wherein the crucible may include a graphite crucible 4 and a quartz crucible 5 located inside the graphite crucible 4, the quartz crucible 5 is used to hold molten silicon 6, the guide tube 1 is arranged above the crucible, the guide tube 1 is in a shape with a large opening at the upper end and a small opening at the lower end, the combined sleeve 2 is built on the inner bottom of the guide tube 1, and the bottom of the combined sleeve 2 extends out of the bottom of the guide tube 1.

[0029] Please refer to Figure 2 , is a schematic diagram of a detection device provided in an embodiment of the present invention. Figure 2 As shown, the detection device for the liquid level position of the molten silicon in the embodiment of the present invention includes a double-headed hook 8 and a detection unit, wherein the double-headed hook 8 is arranged on the inner side of the combined sleeve 2, and in the installed state, the upper end of the double-headed hook 8 is fixedly connected to the side wall of the combined sleeve 2, and the lower end of the double-headed hook 8 extends downward from the bottom of the combined sleeve 2, and the lower end of the double-headed hook 8 will form a clear reflection on the liquid surface of the molten silicon 6, and the detection unit is used to capture the reflection formed by the lower end of the double-headed hook 8 on the liquid surface of the molten silicon 6 and form an image, and the distance between the bottom of the double-headed hook 8 and the liquid surface of the molten silicon 6 can be further calculated based on the reflection imaging, and finally the accurate liquid level position of the molten silicon 6 can be obtained.

[0030] When the combined sleeve 2 is assembled, when a common quartz hook is used to form a reflection on the liquid surface of the silicon melt 6, the reflection of the quartz hook on the liquid surface is easily blurred and unclear due to the interference of the crystal rod 3 because the distance between the quartz hook and the crystal rod 3 is very close. In the crystal pulling equal diameter process stage, the liquid surface of the silicon melt 6 needs to be detected and adjusted in real time. However, since the blurred reflection is difficult to be captured in real time, it is difficult to achieve real-time detection and adjustment of the liquid surface position of the silicon melt 6.

[0031] Therefore, please refer to Figure 3 , is a schematic diagram of a double-ended hook provided in an embodiment of the present invention. Figure 3As shown, the double-headed hook 8 in the embodiment of the present invention may specifically include a plug connector 81, a connecting rod 82 and an imaging body 83, wherein, in the installed state, the upper end of the connecting rod 82 is connected to the plug connector 81, and the lower end of the connecting rod 82 is connected to the imaging body 83, the plug connector 81, the connecting rod 82 and the imaging body 83 may be integrally arranged, the upper portion of the connecting rod 82 may be bent at a certain angle, optionally, for example, the angle is 80° to 90°, one end of the plug connector 81 is connected to the bent end portion of the connecting rod 82, the plug connector 81 is inserted and fixed in the side wall of the combined sleeve 2, thereby realizing the fixation of the spatial position of the double-headed hook 8, and the bent portions of the plug connector 81 and the connecting rod 82 may enable the imaging body 83 to be away from the crystal rod 8 located in the middle area of ​​the combined sleeve 2, and may also enable a certain distance between the imaging body 83 and the inner side wall of the combined sleeve 2, thereby ensuring that a clear reflection may be formed on the liquid surface of the silicon melt 6. Optionally, the imaging body 83 includes a first contact head 81 and a second contact head 82, wherein, in the installed state, the horizontal distance between the first contact head 81 and the axis of the combination sleeve 2 is greater than the horizontal distance between the second contact head 82 and the axis of the combination sleeve 2, that is, the first contact head 81 is farther away from the crystal rod 3 pulled along the axis of the combination sleeve 2 than the second contact head 82, which means that the first contact head 81 is less interfered by the crystal rod 3, and the imaging of the liquid surface of the silicon melt 6 is clearer and will not be blurred, which can ensure the integrity of the reflection during the crystal pulling time, thereby ensuring the real-time detection of the liquid surface of the silicon melt 6 during the pulling process and the accuracy of adjustment.

[0032] In the embodiment of the present invention, in the installed state, the longitudinal cross-section of the plug connector 81 is triangular or polygonal, that is, the plug connector 81 can be formed into a triangular prism or a polygonal prism shape, and a plug hole matching the shape of the plug connector 81 is provided on the side wall of the combined sleeve 2, and the plug connector 81 is inserted into the plug hole to achieve a fixed connection. Moreover, since the longitudinal cross-section of the plug connector is triangular or polygonal, it is ensured that the double-headed hook 8 will not be deflected by the influence of the argon gas flow during the crystal pulling process, thereby avoiding the double-headed hook 8 from being unable to maintain vertical stability and introducing measurement errors.

[0033] In the embodiment of the present invention, the first contact head 831 and the second contact head 832 are formed into a cylindrical shape, that is, in the installed state, the cross-sectional shape of the first contact head 831 and the second contact head 832 are both circular, and the imaging body 83 also includes a connecting block 833, and the connecting block 833 is used to connect the first contact head 831. Specifically, the connecting block 833 is embedded and fixed in the connecting rod 82, and the angle formed by the plug connector 81 and the vertical part of the connecting rod 82 is the same as the angle formed by the connecting block 833 and the vertical part of the connecting rod 82.

[0034] In the embodiment of the present invention, the distance between the bottom of the first contact head 831 and the liquid surface of the silicon melt 6 is greater than the distance between the bottom of the second contact head 832 and the liquid surface of the silicon melt 6, that is, in the vertical direction, the second contact head 832 is closer to the silicon melt 6, so that when the silicon material has just completely melted, the guide tube 1 and the combined sleeve 2 at the lower end thereof can be lowered so that the bottom of the second contact head 832 fixed thereon just contacts with the liquid surface of the silicon melt 6, and the initial liquid surface position of the silicon melt 6 can be determined at this time; after the initial liquid surface position is determined, in the subsequent crystal rod pulling process, the silicon melt 6 will continue to decrease, so that the liquid surface will continue to drop, and at the same time the crucible needs to continue to rise, and in this process, the liquid surface position of the silicon melt 6 needs to be adjusted. Real-time monitoring and precise adjustment can be performed. At this time, a reflection can be formed on the liquid surface of the silicon melt 6 through the first contact head 831. The reflection formed on the liquid surface of the silicon melt 6 by the lower end of the first contact head 831 can be captured by the detection unit and imaged. According to the reflection imaging, the distance between the bottom of the double-headed hook 8 and the liquid surface of the silicon melt 6 can be further calculated, and finally the accurate liquid surface position of the silicon melt 6 can be obtained. In addition, the first contact head 81 is farther away from the crystal rod 3 pulled along the axis of the combined sleeve 2, which means that the first contact head 81 is less interfered by the crystal rod 3, and the image of the liquid surface of the silicon melt 6 is clearer and will not be blurred, which can ensure the integrity of the reflection within the crystal pulling time, thereby ensuring the accuracy of real-time detection and adjustment of the liquid surface of the silicon melt 6 in the pulling process. It can be seen that the first contact head 831 and the second contact head 832 can play different roles at different times.

[0035] In the embodiment of the present invention, the upper end of the first contact head 831 is fixedly connected to the bottom surface of the connecting block 833, and the bottom surface of the connecting block 833 is formed into a polygon, such as a rectangle, a pentagon, a hexagon, etc., thereby, the connecting block 833 will form a reflection on the liquid surface of the silicon melt 6 together with the first contact head 831, and the polygonal shape makes the reflection formed by the bottom of the first contact head 831 on the liquid surface of the silicon melt 6 clearer, which is conducive to the real-time and accurate detection of the liquid level position of the silicon melt 6.

[0036] In the embodiment of the present invention, the connecting rod 82 can be an integral structure with the second contact head 832, that is, in the vertical state, the lower end of the connecting rod 82 is directly formed into a cylindrical second contact head 832; of course, the connecting block 833 and the first contact head 831 can also be an integral structure, and there is a certain distance between the first contact head 831 and the second contact head 832 to ensure that the reflections of the two on the liquid surface of the silicon melt 6 will not be connected into one piece, so as not to increase the difficulty of detection and reduce the accuracy of detection.

[0037] In the embodiment of the present invention, optionally, the detection unit is a CCD camera, and the detection unit can image by acquiring the reflection of the first contact head 831 on the liquid surface of the silicon melt 6, and then calculate and analyze the liquid surface position of the silicon melt 6.

[0038] like Figure 4-8 As shown, in the embodiment of the present invention, the combined sleeve 2 is arranged in the guide tube 1, and the combined sleeve 2 may include: an inner tube 21, an insulation layer 22 and an outer tube 23, wherein the minimum inner diameter of the inner tube 21 is greater than the diameter of the crystal rod 3, so that the crystal rod 3 can pass through the internal space of the inner tube 21; and the outer tube 23 is sleeved outside the inner tube 21, and a circle of outer flange is formed at one end of the outer tube 23, and the outer flange is used to overlap with the bottom of the guide tube 1, that is, the combined sleeve 2 is arranged at the bottom of the guide tube 1, and the inner diameter of the guide tube 1 gradually decreases. The combined sleeve 2 can be laid on the inner wall of the guide tube 1 by the outer flange to achieve limited fixation; the insulation layer 22 is arranged between the inner tube 21 and the outer tube 23, and the insulation layer 22 has a good thermal insulation effect. By arranging the combined sleeve 2 at the inner bottom of the guide tube 1, the adjustable range of the axial temperature difference G of the crystal rod can be widened, and then the difference ΔG between the axial temperature difference at the edge of the crystal rod and the axial temperature difference at the center of the crystal rod is close to the ideal value, so as to obtain a larger crystal rod with a defect-free area, thereby improving the overall quality of the grown crystal rod.

[0039] In some embodiments of the present invention, the inner diameter of the inner cylinder 21 gradually decreases from one end to the other end, that is, in the vertically installed state, the inner diameter of the inner cylinder 21 gradually decreases from top to bottom, and the axial cross-section of the inner cylinder 21 is conically arranged, that is, the thickness of the inner cylinder 21 gradually increases from top to bottom. By setting the inner cylinder 21 into such a shape, the thicker bottom of the inner cylinder 21 can be used to well block a part of the heat transferred by the high-temperature melt below, so as to avoid the problem that the axial temperature difference at the edge of the crystal rod becomes smaller, while the axial temperature difference at the center of the crystal rod remains basically unchanged, thereby increasing ΔG.

[0040] In some optional embodiments, the material of the inner cylinder 21 and the outer cylinder 23 can be any one of graphite and molybdenum. The inner cylinder 21 and the outer cylinder 23 can be made of the same material or different materials. The chemical properties of graphite and molybdenum are stable, corrosion-resistant and high-temperature resistant, which can ensure stability in a high-temperature single crystal furnace.

[0041] like Figure 6As shown, in some embodiments of the present invention, the heat insulation layer 22 is arranged between the inner cylinder 21 and the outer cylinder 23, and the side wall of the heat insulation layer 22 is evenly distributed with a plurality of heat conduction holes 221. Since the heat insulation layer 22 has a good heat insulation effect, and a certain amount of heat can be transmitted to the surface of the crystal rod 3 through the heat conduction holes 221, the heat value transmitted to the surface of the crystal rod 3 can be controlled by controlling the number of heat conduction holes 221, thereby realizing the regulation and control of the axial temperature difference of the crystal rod 3, so that the crystal rod obtains a larger defect-free area. In an optional embodiment, the heat insulation layer 22 can be specifically a carbon fiber heat insulation felt, which has a good heat insulation effect and is resistant to high temperatures, and can adapt to the high temperature in the single crystal furnace.

[0042] like Figure 7-8 As shown, in the embodiment of the present invention, the outer circumferential surface of the outer cylinder 23 is formed with a plurality of annular convex patterns, and the plurality of annular convex patterns are arranged at intervals along the axial direction of the outer cylinder 23. These annular convex patterns can increase the axial transmission of heat, so that the axial temperature difference of the crystal rod 3 is maintained within a relatively ideal range, so as to form an environment conducive to the growth of defect-free crystal rods. In some optional embodiments, the plurality of annular convex patterns can be wavy around the outer circumference of the outer cylinder 23, or can be spirally around the outer circumference of the outer cylinder 23.

[0043] In some embodiments of the present invention, a monitoring gap is provided on the same side of the inner cylinder 21, the thermal insulation layer 22 and the outer cylinder 23, and the monitoring gap is used to provide a monitoring channel for the crystal rod diameter monitoring unit 7 (Auto Diameter Control, ADC for short); that is, since the combined sleeve 2 is arranged at the bottom of the guide cylinder 1 and surrounds the crystal rod 3, in order to facilitate real-time monitoring of the diameter of the crystal rod 3, it is necessary to provide a monitoring gap on the combined sleeve 2, that is, to provide a monitoring gap on the same side of the inner cylinder 21, the thermal insulation layer 22 and the outer cylinder 23 to provide a detection channel, so that the crystal rod diameter monitoring unit 7 can monitor the diameter of the crystal rod 3 through the monitoring gap.

[0044] In summary, the detection device according to the embodiment of the present invention utilizes a double-headed hook to form a stable and clear reflection on the surface of the silicon melt, so that the detection unit can accurately capture the reflection and then measure the exact position of the silicon melt surface, thereby ensuring the accuracy of the adjustment of various parameters during the crystal pulling process and improving the quality of the obtained crystal rod.

[0045] Another embodiment of the present invention further provides a single crystal furnace, the single crystal furnace comprising a crucible and a guide tube and a combined sleeve located directly above the crucible, the combined sleeve being arranged at the opening of the inner bottom of the guide tube, and the single crystal furnace further comprising a detection device for the position of the liquid level of the molten silicon as described in the above embodiment. Since the detection device in the above embodiment has the above beneficial effects, the single crystal furnace in the embodiment of the present invention also has the above beneficial effects accordingly, and in order to avoid repetition, it will not be described here.

[0046] The above are some embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A device for detecting the liquid level of silicon melt, applied to a single crystal furnace, wherein the single crystal furnace comprises a crucible, a guide tube and a combined sleeve located directly above the crucible, wherein the combined sleeve is arranged at an opening of the inner bottom of the guide tube, It is characterized in that The detection device comprises: A double-ended hook, wherein the double-ended hook is located on the inner side of the combined sleeve, the upper end of the double-ended hook is fixedly connected to the side wall of the combined sleeve, and the lower end of the double-ended hook extends downward from the bottom of the combined sleeve to form a reflection on the surface of the silicon melt; A detection unit, the detection unit is used to capture the reflection image formed by the lower end of the double-headed hook on the liquid surface of the silicon melt; The double-headed hook includes a plug connector, a connecting rod and an imaging body, the imaging body includes a first contact head and a second contact head, the first contact head and the second contact head are formed into a cylinder, the imaging body also includes a connecting block, the connecting block is fixedly connected to the connecting rod, the upper end of the first contact head is fixedly connected to the bottom surface of the connecting block, and the bottom surface of the connecting block is formed into a polygon.

2. The detection device according to claim 1, It is characterized in that The two ends of the connecting rod are respectively connected to the plug connector and the imaging body, the plug connector is inserted and fixed in the side wall of the combination sleeve, and the horizontal distance between the first contact head and the axis of the combination sleeve is greater than the horizontal distance between the second contact head and the axis of the combination sleeve.

3. The detection device according to claim 2, It is characterized in that The longitudinal cross section of the plug connector is triangular or polygonal, and the side wall of the combined sleeve is provided with a plug hole matching the shape of the plug connector.

4. The detection device according to claim 1, It is characterized in that The detection unit is a CCD camera.

5. The detection device according to claim 2, It is characterized in that The distance between the bottom of the first contact head and the surface of the molten silicon is greater than the distance between the bottom of the second contact head and the surface of the molten silicon.

6. The detection device according to claim 2, It is characterized in that The connecting rod and the second contact head are an integral structure.

7. The detection device according to claim 1, It is characterized in that The combined sleeve comprises an inner tube, an outer tube and a heat insulation layer, wherein the outer tube is sleeved on the outer periphery of the inner tube, the heat insulation layer is arranged between the inner tube and the outer tube, a plurality of heat conduction holes are evenly distributed on the side wall of the heat insulation layer, a plurality of annular grooves are formed on the outer peripheral surface of the outer tube, and the plurality of annular grooves are arranged at intervals along the axial direction of the outer tube.

8. The detection device according to claim 7, It is characterized in that The material of the inner cylinder is graphite material, and the material of the heat insulation layer is carbon fiber heat insulation felt.

9. A single crystal furnace, It is characterized in that The single crystal furnace includes a crucible, a guide tube and a combined sleeve located directly above the crucible, the combined sleeve is arranged at the opening of the inner bottom of the guide tube, and also includes a detection device for the liquid level position of the silicon melt as described in any one of claims 1-8.

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