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CN-122015709-A - Method for evaluating opening degree of straight-pulled monocrystalline silicon shoulder-relief edge line

CN122015709ACN 122015709 ACN122015709 ACN 122015709ACN-122015709-A

Abstract

The invention discloses a method for evaluating the opening degree of a straight-pulled monocrystalline silicon shoulder-line, and belongs to the field of straight-pulled monocrystalline silicon growth. The method comprises the steps of (1) obtaining a shouldering image in a single crystal furnace in real time through an image acquisition system, (2) processing the image, determining the edge of the crystal bar, respectively calculating the maximum diameter D max of the circular arc represented by the shouldering crystal bar and the minimum diameter D min of the circular arc represented by the ridge line after the shouldering, calculating evaluation parameters at least comprising the opening degree delta D and the opening tendency degree K, wherein the opening degree delta D=D max -D min , the opening tendency degree K is the ratio of the change rate of D max to the change rate of D min , and (4) comparing the opening degree delta D and the opening tendency degree K with a preset threshold range, evaluating the state of the shouldering process based on the comparison result, and outputting evaluation information. The method can effectively avoid the edge and line breakage, improve the shoulder success rate and the production efficiency, and reduce the dependence on the experience of operators.

Inventors

  • NING YONGDUO
  • Gu Ximeng
  • YAN JUNYAO

Assignees

  • 山东有研半导体材料有限公司
  • 有研半导体硅材料股份公司

Dates

Publication Date
20260512
Application Date
20251230

Claims (10)

  1. 1. A method for evaluating the opening degree of a straight-pulled monocrystalline silicon shoulder-strap edge line, which is characterized by comprising the following steps: (1) Acquiring a shouldering image in the single crystal furnace in real time through an image acquisition system; (2) Processing the image, determining the edge of the crystal bar, and respectively calculating to obtain the maximum diameter D max of the representative circular arc of the shouldered crystal bar and the minimum diameter D min of the representative ridge line after the ridge is opened; (3) Calculating an evaluation parameter, wherein the evaluation parameter at least comprises an opening degree delta D and an opening trend degree K, and the opening degree delta D=D max -D min , and the opening trend degree K is the ratio of the change rate of D max to the change rate of D min ; (4) And comparing the opening edge degree delta D and the opening edge trend degree K with a preset threshold range, evaluating the state of the shoulder placing process based on a comparison result, and outputting evaluation information.
  2. 2. The method for evaluating the degree of opening of a shoulder-line of a czochralski crystal of claim 1, wherein in step (2), the image is subjected to graying, edge detection, and contour fitting to determine the edge of the ingot.
  3. 3. The method for evaluating the edge opening degree of the straight pulled single crystal shouldered edge line according to claim 2, wherein the algorithm adopted by the edge detection is a Sobel operator, a Canny edge detection or a Scharr operator.
  4. 4. The method for evaluating the opening degree of a straight-pulled single-crystal shouldered ridge according to claim 1, wherein in the step (3), the opening tendency degree K is calculated by deriving the change curves of D max and D min with time or the crystal length respectively to obtain the change rates V max and V min , and calculating k=v max /V min .
  5. 5. The method for evaluating the opening degree of a straight pulled single crystal shoulder line according to claim 1, wherein in the step (4), the preset threshold range of the opening degree Δd is 0 to 4mm, and the preset threshold range of the opening tendency degree K is 1.0 to 1.4.
  6. 6. The method for evaluating the opening degree of a straight-pulled single-crystal shouldered ridge according to claim 5, wherein in the step (4), the evaluation information comprises that when the opening tendency degree K is 1.0, the edge line is evaluated to be not opened, or the maximum diameter and the minimum diameter of the edge line after opening are amplified in parallel, when the opening tendency degree K is between 1.0 and 1.4, the single-crystal is evaluated to be being opened at an increased speed, and when the opening tendency degree K is greater than 1.4, the straight-pulled single-crystal is evaluated to be too fast in shouldered, and the risk of broken edges or broken lines exists.
  7. 7. The method for evaluating the degree of opening of a shoulder line of a Czochralski crystal of claim 1, wherein the evaluation information output in step (4) is used to prompt adjustment of crystal pulling process parameters including pull rate and heating power.
  8. 8. The method for evaluating the opening degree of a straight-pulled single-crystal shoulder-line according to claim 7, wherein if the opening tendency degree value increases and the opening degree is also continuously increasing, the pulling speed is increased or a temperature-rise temperature control closed loop is opened to raise the temperature, after the pulling speed or the temperature control is adjusted, the opening tendency degree and the opening degree are continuously monitored in real time, if the opening tendency degree has a decreasing tendency, the temperature-rise temperature control closed loop is closed, and if the opening tendency degree value decreases rapidly, the pulling speed is reduced.
  9. 9. The method for evaluating the opening degree of the straight pulled single crystal shouldering ridge according to claim 1, wherein the steps (1) to (4) are circularly executed with 10-60 seconds as a period, so that the real-time monitoring and evaluation of the shouldering process are realized.
  10. 10. A czochralski silicon, characterized in that, in the shoulder-strap stage of the czochralski silicon, the degree of opening of the shoulder-strap edge of the czochralski silicon is evaluated by the method of any one of claims 1 to 9.

Description

Method for evaluating opening degree of straight-pulled monocrystalline silicon shoulder-relief edge line Technical Field The invention relates to a method for evaluating the opening degree of a straight-pulled monocrystalline silicon shoulder-line, belonging to the field of straight-pulled monocrystalline silicon growth. Background The Czochralski method, also called Czochralski method, is characterized in that high-purity polysilicon is put into a quartz crucible, heated and melted in a single crystal furnace, and then pulled into a crystal rod by using seed crystals with a certain crystal orientation, is the most main and most extensive method for preparing silicon single crystals in the semiconductor industry at present, and accounts for more than 90% of the production quantity of all silicon single crystals. The technological process mainly comprises the following steps of loading, melting, stabilizing, seeding, shouldering, isodiametric and ending, wherein the shouldering is the most critical technological step affecting crystallization, and the main purpose of the step is to stably and controllably amplify the diameter of the defect-free fine crystal after dislocation removal to the diameter of a target crystal rod, thereby laying a foundation for subsequent isodiametric growth. Currently mainstream single crystal silicon products of 8 inch, 12 inch and larger sizes, mostly single crystals with <100> crystal orientation, have four ridge stripes, called four ridge lines. When the silicon single crystal with the <100> crystal orientation is produced and shouldered, if the shouldering is rapid, the (111) crystal face group can be gradually opened from the prismatic line state and then grows in a plane shape or a step shape along with the continuous expansion of the diameter, namely four open edges or wide faces are formed, as shown in figure 1. In the traditional crystal pulling experience, the opening degree of the ridge, namely the expansion speed of an open edge and a wide surface, is not too high, and the ridge is easy to break to form polycrystal. And (3) when the supercooling degree of the silicon single crystal growth is large by the crystal face elimination rule and the periodic bond chain theory, the (111) crystal face can be continuously unfolded until the shoulder top view of the whole shouldered part is nearly square. Therefore, the diameter expansion speed at the 'wide face' needs to be detected and evaluated and is matched with the diameter expansion speed at the circular arc in the shouldering process, the matching relation of the diameter expansion speed and the crystal growth principle is related to the silicon single crystal structure, if the growth speed is not matched, the diameter increase at the shouldering stage is too fast, the (111) crystal face is not fast enough to grow out of the step face, the single crystal is easy to break, the remelting of the heavy head is easy to start, the conical shoulder is generated when the diameter increase is too slow, and as shown in fig. 2, raw materials are wasted and the production cost is increased. In the current main flow shouldering process, thin single crystal rods at the end of seeding are grown to the required size through the shouldering stage mainly through process settings such as the crystal rising speed, the temperature change and the like in a shouldering stage process slope table, but the capability of detecting and evaluating the excessive speed and the excessive speed of shouldering is not provided, and some single crystal furnace equipment can provide data of the shouldering angle, but the capability of detecting and evaluating the edge line opening degree is not provided. With continuous production of enterprises, a furnace thermal field is gradually aged, shoulder-making and edge-breaking of a certain stable-production crystal pulling process can occur continuously for several times, and the reason is that parameters such as temperature, pulling speed and the like in a process slope table are not matched with the current environment any more, so that the edge-making and edge-breaking of a shoulder-making edge line is not performed according to an ideal shape, and the production efficiency is seriously affected. When the situation is met, the existing solution is that engineers and operators follow up the shoulder placing process by utilizing a centralized control system on a production site or remotely, the edge opening degree of the shoulder placing edge line is judged at any time so as to manually adjust the process parameters, the method has the advantages that the process can be adjusted at any time, the shoulder placing success rate is high, but the method has the disadvantages that firstly, the cost of labor is high, the repeatability is poor, secondly, the method needs to rely on abundant manual experience, and a new employee does not have the operability. In summary, the invention provides a method for evaluating th