Auxiliary device for liquid level calibration of single crystal furnace

Abstract

The utility model provides a single crystal furnace liquid level calibration auxiliary device, which comprises a camera, a liquid level reference rod and a liquid level calibration rod, the liquid level reference rod is arranged between a guide cylinder and a crucible and is used for indicating the initial liquid level of silicon liquid in the crucible; and in the lifting process of the crucible, the inverted image of the liquid level calibration rod in the silicon liquid provides a camera shooting reference point for the camera. According to the liquid level calibration auxiliary device for the single crystal furnace, the crucible lifting proportion coefficient is obtained by collecting the pixel difference and the crucible lifting ratio in advance, and the distance from the liquid level calibration rod to the fixed point on the guide cylinder is monitored in the crystal pulling process to assist in monitoring and regulating the liquid level, so that the accurate regulation of the liquid level of silicon liquid is realized, and the accuracy of the crystal pulling process is improved. Errors caused by different crucible sizes and different positions of silicon liquid in a conventional liquid level monitoring method are avoided, the single crystal defect caused by fluctuation of the liquid level position is avoided, and a foundation is laid for an advanced process.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor production, in particular to a single crystal furnace liquid level calibration auxiliary device. Background Art

[0002] When producing single crystal silicon rods, a heater is needed to heat the polysilicon material in the crucible until it melts, and then the direct pulling method is used to pull the single crystal silicon rod. During the process of pulling the single crystal silicon rod, due to the reduction of silicon liquid, the height of the crucible needs to be raised to ensure a stable liquid level, so that the crystal pulling is smooth and the crystal pulling quality is guaranteed.

[0003] The methods used to monitor the liquid level in the prior art include the "weight method-center of circle method". The CZ single crystal furnace calculates the weight of the remaining material in the crucible through a weight sensor, and sets the weight loss of one kilogram of silicon material-crucible lifting distance in the program, so that the system will calculate a target liquid level value, and the camera on the single crystal furnace measures a current liquid level value by capturing pixel values. The system adjusts the crucible lifting speed by comparing the current liquid level value with the target liquid level value to control the liquid surface distance. The disadvantage of this method is that the weight loss of one kilogram of silicon material-crucible lifting distance value varies with the inner diameter of the crucible and the position of the silicon liquid in the crucible, and the difference is large, so the liquid surface distance cannot be accurately controlled. Utility Model Content

[0004] The utility model aims to provide a single crystal furnace liquid level calibration auxiliary device to solve the above-mentioned problems.

[0005] The technical solution adopted by the utility model is: a single crystal furnace liquid level calibration auxiliary device, which includes: a camera, a liquid level reference rod and a liquid level calibration rod, the liquid level reference rod is arranged between the guide tube and the crucible, and is used to indicate the initial liquid level of the silicon liquid in the crucible; during the lifting and lowering process of the crucible, the reflection of the liquid level calibration rod in the silicon liquid provides a shooting reference point for the camera.

[0006] Preferably, the liquid level reference rod is in an inverted L-shape, and penetrates through and is hung on the lower edge of the guide tube.

[0007] Preferably, a limit portion is provided at the transverse end of the liquid level reference rod, and the limit portion is clamped to the lower edge of the guide tube.

[0008] Preferably, the bottom end of the liquid level reference rod is 20 cm to 30 cm away from the lower edge of the guide tube.

[0009] Preferably, the liquid level calibration rod comprises a vertical portion and a horizontal portion, the top of the vertical portion is provided with a thread, which passes through the lower edge of the guide tube and is fastened by a nut.

[0010] Preferably, the length of the vertical portion is 50 mm to 80 mm.

[0011] Preferably, the horizontal portion extends 20 mm to 30 mm in a direction away from the axis of the guide tube.

[0012] Preferably, the liquid level reference rod is a quartz liquid level reference rod, and the liquid level calibration rod is a quartz liquid level calibration rod.

[0013] Preferably, the camera is a CCD camera, which is installed on the single crystal furnace wall above the liquid level calibration rod.

[0014] The beneficial effect of the utility model is that the single crystal furnace liquid level calibration auxiliary device obtains the crucible lifting proportional coefficient by pre-collecting the pixel difference and the crucible lifting ratio, and then monitors the distance from the liquid level calibration rod to the fixed point on the guide tube during the crystal pulling process to assist in monitoring and regulating the liquid level, thereby realizing precise regulation of the silicon liquid level, avoiding the errors caused by the different crucible sizes and the positions of the silicon liquid therein in the conventional liquid level monitoring methods, avoiding the single crystal defects caused by the fluctuations in the liquid level position, and laying a foundation for advanced processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the overall structure diagram of the embodiment of the utility model;

[0016] Figure 2 It is a structural diagram of the liquid level reference rod in the embodiment of the utility model;

[0017] Figure 3 It is a structural diagram of the liquid level calibration rod in the embodiment of the utility model.

[0018] In the figure:

[0019] 1. Camera; 2. Liquid level reference rod; 2-1. Limiting part; 3. Liquid level calibration rod; 3-1. Vertical part; 3-2. Horizontal part; 4. Flow guide tube; 5. Crucible; 6. Nut. DETAILED DESCRIPTION

[0020] The technical solution of the embodiment of the utility model is described in detail below with reference to the accompanying drawings.

[0021] In the description of the embodiments of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "set" and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood by specific circumstances.

[0022] Reference Figure 1 , a single crystal furnace liquid level calibration auxiliary device, comprising: a camera 1, a liquid level reference rod 2 and a liquid level calibration rod 3, the liquid level reference rod 2 is arranged between the guide tube 4 and the crucible 5, and is used to indicate the initial liquid level of the silicon liquid in the crucible 5; the liquid level calibration rod 3 is arranged between the guide tube 4 and the crucible 5, the camera 1 is a CCD camera, which is installed on the single crystal furnace wall above the liquid level calibration rod 3, during the lifting process of the crucible 5, the reflection of the liquid level calibration rod 3 in the silicon liquid provides a shooting reference point for the camera 1.

[0023] The method of using this auxiliary device is:

[0024] (1) Before collecting the liquid level calibration coefficient, lift the crucible 5 so that the bottom end of the liquid level reference rod 2 contacts the silicon liquid. At this time, the distance between the lower edge of the guide tube 4 and the silicon liquid is the length of the liquid level reference rod 2. Then lower the height of the crucible 5. In the process of lowering the height of the crucible 5, the distance from the lower edge of the guide tube 4 to the surface of the silicon liquid is always quantifiable and controllable.

[0025] (2) When the height of the crucible 5 is lowered to an appropriate position (referring to an appropriate silicon liquid level), the camera 1 is used to collect pixel values ​​of a first image including the reflection of the liquid level calibration rod 3 in the silicon liquid. After the crucible 5 is raised (or lowered) to a specified height, the camera 1 is used to collect pixel values ​​of a second image including the reflection of the liquid level calibration rod 3 in the silicon liquid. During the two image collection processes, the reflection of the liquid level calibration rod 3 in the silicon liquid is always the camera reference point of the camera 1. After the collection is completed, the above data is transmitted to the computer system through the camera 1. The computer system subtracts the first image pixel value from the second image pixel value and divides it by the specified height of the crucible 5 to obtain the crucible 5 lifting and lowering proportional coefficient. In specific implementation, the above crucible 5 lifting and lowering proportional coefficient should be obtained through multiple data collection and analysis.

[0026] (3) Before single crystal pulling, camera 1 collects the distance between the reflection of liquid level calibration rod 3 in silicon liquid and a calibration point (an arbitrary point specified artificially) on guide tube 4, as well as the pixel value of the third image including the reflection of liquid level calibration rod 3 in silicon liquid at this time; during single crystal pulling, camera 1 monitors in real time the distance between the reflection of liquid level calibration rod 3 in silicon liquid and the above calibration point, as well as the pixel value of the fourth image including the reflection of liquid level calibration rod 3 in silicon liquid at this time. When the distance does not meet the preset value, the computer system calculates the distance that crucible 5 should be raised or lowered based on the difference between the third image pixel value and the fourth image pixel value and the lifting ratio coefficient of crucible 5, and controls its lifting or lowering, so that the silicon liquid level is accurately regulated to ensure smooth crystal pulling and high crystal pulling quality.

[0027] In this embodiment, the liquid level reference rod 2 and the liquid level calibration rod 3 are both detachably arranged at the lower edge of the guide tube 4. Figure 2 The liquid level reference rod 2 is in an inverted L shape, and a limit portion 2-1 is provided at its transverse end. When installed on the guide tube 4, the vertical end of the liquid level reference rod 2 passes through the lower edge of the guide tube 4, and the transverse end rests on the inner side of the guide tube 4. During the initial calibration of the liquid level, the guide tube 4 does not rise or fall or move, and the vertical end of the liquid level reference rod 2 remains vertical. After completing the above-mentioned initial calibration process, the liquid level reference rod 2 has no effect in this production cycle. During the single crystal production process, the lifting and lowering of the guide tube 4 may cause the liquid level reference rod 2 to shake. At this time, the limit portion 2-1 clamps the above-mentioned through hole to prevent the liquid level reference rod 2 from falling.

[0028] In this embodiment, the liquid level reference rod 2 is used to find the initial liquid level, so that in the subsequent data collection and liquid level control process, the distance between the silicon liquid surface and the lower edge of the guide tube 4 is measurable and controllable.

[0029] In some implemented embodiments, the bottom end of the liquid level reference rod 2 is 20 cm to 30 cm away from the bottom edge of the guide tube 4. Generally, the distance is a whole ten to facilitate the first step of lowering the crucible 5 and adjusting the silicon liquid level to a specified height.

[0030] Reference Figure 3The liquid level calibration rod 3 includes a vertical portion 3-1 and a horizontal portion 3-2. The top of the vertical portion 3-1 is provided with a thread, which penetrates the lower edge of the guide tube 4 and is fastened by a nut 6; the horizontal portion 3-2 extends in a direction away from the axis of the guide tube 4, which can make its reflection in the silicon liquid more obvious, and will not accidentally touch the single crystal silicon rod to avoid breaking the bud. Compared with directly using the reflection of the lower edge of the guide tube 4 for data collection and liquid level control, adding the liquid level calibration rod 3 can make the reflection signal stable. This is because the lower edge area of ​​the guide tube 4 is large. During the lifting process of the crucible 5, its reflection in the silicon liquid will appear blurred or disappear, and it is impossible to provide a stable camera reference point for the camera 1, which makes the collection and calculation of the lifting proportional coefficient of the crucible 5 inaccurate, and the subsequent crucible lifting distance and silicon liquid level adjustment inaccurate.

[0031] In some feasible embodiments, the length of the vertical portion 3 - 1 of the liquid level calibration rod 3 is 50 mm to 80 mm, and the length of the horizontal portion 3 - 2 is 20 mm to 30 mm.

[0032] In order to prevent impurities from falling into the silicon liquid, the liquid level reference rod 2 is configured as a high-temperature resistant quartz liquid level reference rod 2, and the liquid level calibration rod 3 is a high-temperature resistant quartz liquid level calibration rod 3.

[0033] Compared with the prior art, the single crystal furnace liquid level calibration auxiliary device obtains the crucible 5 lifting and lowering proportional coefficient by pre-collecting the pixel difference and the crucible lift ratio, and then monitors the distance from the liquid level calibration rod 3 to the fixed point on the guide tube 4 during the crystal pulling process to assist in monitoring and controlling the liquid level, thereby achieving precise control of the silicon liquid level, avoiding the errors caused by the different sizes of the crucible 5 and the position of the silicon liquid therein in conventional liquid level monitoring methods, and avoiding single crystal defects caused by fluctuations in the liquid level position, thus laying the foundation for advanced processes.

[0034] The above are preferred implementations of the present utility model. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present utility model. These improvements and modifications should also be regarded as the protection scope of the present utility model.

Claims

1. A single crystal furnace liquid level calibration auxiliary device, characterized in that: include: A camera, a liquid level reference rod and a liquid level calibration rod, wherein the liquid level reference rod is arranged between the guide tube and the crucible and is used to indicate the initial liquid level of the silicon liquid in the crucible; During the lifting and lowering process of the crucible, the reflection of the liquid level calibration rod in the silicon liquid provides a photographing reference point for the camera.

2. The single crystal furnace liquid level calibration auxiliary device according to claim 1, characterized in that: The liquid level reference rod is in an inverted L shape, and penetrates through and is hung on the lower edge of the guide tube.

3. The single crystal furnace liquid level calibration auxiliary device according to claim 2, characterized in that: A limiting portion is provided at the transverse end of the liquid level reference rod, and the limiting portion is clamped to the lower edge of the guide tube.

4. The single crystal furnace liquid level calibration auxiliary device according to claim 2, characterized in that: The bottom end of the liquid level reference rod is 20 cm to 30 cm away from the lower edge of the guide tube.

5. The single crystal furnace liquid level calibration auxiliary device according to any one of claims 1 to 4, characterized in that: The liquid level calibration rod comprises a vertical portion and a horizontal portion. A thread is provided at the top of the vertical portion, which passes through the lower edge of the guide tube and is fastened by a nut.

6. The single crystal furnace liquid level calibration auxiliary device according to claim 5, characterized in that: The length of the vertical portion is 50 mm to 80 mm.

7. The single crystal furnace liquid level calibration auxiliary device according to claim 5, characterized in that: The horizontal portion extends 20 mm to 30 mm in a direction away from the axis of the guide tube.

8. The single crystal furnace liquid level calibration auxiliary device according to any one of claims 1-4, 6-7, characterized in that: The liquid level reference rod is a quartz liquid level reference rod, and the liquid level calibration rod is a quartz liquid level calibration rod.

9. The single crystal furnace liquid level calibration auxiliary device according to claim 8, characterized in that: The camera is a CCD camera, which is installed on the single crystal furnace wall above the liquid level calibration rod.

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