Method for controlling stability of wide surface in isometric stage of crystal orientation monocrystalline silicon

Abstract

The invention discloses a 1t; 111gt, 111gt; the invention relates to a method for controlling the stability of a wide surface at an equal-diameter stage of crystal orientation monocrystalline silicon, which comprises the following steps of: (1) after the equal-diameter diameter is stabilized, sequentially recording the variation range of the diameter of the monocrystalline silicon when the crystal rotates a circle at a diameter stabilizing position A, a diameter stabilizing position B and a diameter stabilizing position C through a client of the monocrystalline furnace, and calculating the difference values delta A1, delta A2 and delta A3 between the maximum diameter and the minimum diameter; (2) calculating diameter change rates alpha = (deltaA2-deltaA1) / deltad (B-A) and beta = (deltaA3-deltaA2) / deltad (C-B); comparing the values of alpha and beta; if alpha is greater than or equal to beta, maintaining the existing pulling speed to continuously grow the single crystal; if alpha is smaller than beta, the melt temperature is reduced to T2 from T1, and meanwhile, the pulling speed is reduced to V2 from V1 until alpha is larger than or equal to beta; and (3) repeating the steps (1) and (2), and controlling the diameter difference value of the single crystal after rotating for a circle within a range of 2mm. By adopting the method, the 1t can be produced by a Czochralski method; 111gt, 111gt; the wide surface change is dynamically judged in the crystal orientation single crystal silicon process, and the size of the wide surface is timely and effectively adjusted, so that the stability control of the wide surface change in the equal diameter stage is realized, and the single crystal quality is improved.

Description

Technical Field

[0001] The present invention relates to a method for controlling the stability of the wide face during the isodiameter stage of <111>-oriented single crystal silicon, and belongs to the field of semiconductor silicon material production. Background Art

[0002] During the growth of <111>-oriented single crystal silicon by the Czochralski method, the anisotropic characteristics of crystal growth will significantly affect the geometric morphology of the crystal. Due to the influence of the surface energy difference and atomic attachment kinetic characteristics between different crystal planes in the <111> crystal orientation of the silicon crystal, preferential growth is likely to occur at the crystal plane with smaller nucleation energy (such as the {112} or {110} crystal plane) at the solid-liquid growth interface, and the appearance shows a wide face structure. The spontaneous expansion of this wide face will cause the crystal cross-section to deviate from the ideal circular contour, and the actual diameter shows periodic fluctuations in the circumferential direction. Traditional diameter control strategies are mainly based on the global optimization of the thermal field and the adjustment of crystal pulling parameters. In the existing single crystal silicon growth process, wide faces (i.e., flat areas on the crystal surface) are likely to appear during the isodiameter stage, and these wide faces may cause the following problems: an increase in crystal surface defects, affecting device performance; the non-uniformity of the wide face leads to enhanced crystal anisotropy and reduced yield. In the prior art, fixed process parameters are usually adopted, lacking a monitoring and adjustment method for the wide face of <111>-oriented single crystal silicon, making it difficult to adapt to the complex changes in crystal growth during the isodiameter stage and difficult to effectively suppress the formation of wide faces. Summary of the Invention

[0003] Based on the above problems existing in the prior art, the purpose of the present invention is to provide a method for controlling the stability of the wide face during the isodiameter stage of <111>-oriented single crystal silicon. By using this method, it is possible to dynamically judge the change of the wide face during the production of <111>-oriented single crystal silicon by the Czochralski method, timely and effectively adjust the size of the wide face, so as to achieve the stability control of the wide face change during the isodiameter stage and improve the single crystal quality.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for controlling the stability of the wide face during the isodiameter stage of <111>-oriented single crystal silicon, the method comprising the following steps:

[0006] (1) After the isodiameter is stable, sequentially record the change ranges of the single crystal diameter per revolution of the crystal at the diameter stable positions A, B, and C through the single crystal furnace client, and calculate the differences ΔA1, ΔA2, and ΔA3 between the maximum diameter and the minimum diameter;

[0007] (2) Calculate the diameter change rate α = (ΔA2 - ΔA1) / Δd (B-A) , β = (ΔA3 - ΔA2) / Δd (C-B) , where Δd (B-A)is the length from position B to position A, Δd (C-B) is the length from position C to position B;

[0008] Compare the values of α and β:

[0009] If α ≥ β, it indicates that the width face has a tendency to decrease or no longer increase, and the existing pulling speed is maintained to continue growing the single crystal;

[0010] If α < β, it indicates that the width face has a tendency to increase. The melt temperature is reduced from T1 to T2, and at the same time, the pulling speed is reduced from V1 to V2 until α ≥ β;

[0011] (3) Thereafter, steps (1) and (2) are cyclically repeated at intervals of every 5 mm increase in the length of the equal-diameter crystal, and the diameter difference of one full rotation of the single crystal during the equal-diameter process is always controlled below 2 mm, preferably below 1 mm.

[0012] Further, the length Δd from position B to position A (B-A) is equal to the length Δd from position C to position B (C-B) The smaller this length is controlled, the more accurate the control of the single crystal growth interface can be ensured. However, if it is too small, the operation will be too frequent. Therefore, the length preferably taken is 4 - 8 mm, more preferably 5 mm.

[0013] Further, manually control the actual diameter size in the early stage of equal-diameter to meet the target diameter size. When the pulling speed change trend in the early stage of equal-diameter approaches the growth setting and the single crystal diameter change tends to be stable, check that the signal of the diameter measurement system is normal, calibrate the single crystal furnace diameter measurement signal, and enable automatic diameter control.

[0014] Further, in the step (1), the diameter signal is captured once every 1 second, that is, the diameter signal capture frequency is 1 time / second.

[0015] Further, in the step (2), the adjustment range of the melt temperature T is 3 - 5 sp / hr, and the adjustment range of the pulling speed V is 3 - 5 mm / hr.

[0016] Advantages of the present invention:

[0017] The present invention first proposes a method for dynamically judging and regulating the size of the wide face in the isodiametric stage of <111>-oriented single-crystalline silicon, that is, by calculating the difference in diameter values caused by the wide face when the single crystal rotates one week during the isodiametric process, comparing the differences in diameter within two consecutive lengths to judge the changing trend of the wide face size, and then giving a regulation mechanism for maintaining the stability of the wide face size from the aspects of temperature and drawing speed. The present invention provides a theoretical basis for accurately judging the change in the size of the growing wide face in the isodiametric stage of <111>-oriented single crystal, and provides technical guidance for regulating temperature and drawing speed to maintain the wide face size, which can help solve the problems that it is impossible to intuitively judge the size of the growing wide face and regulate the change in the wide face size during the isodiametric stage of single-crystalline silicon.

[0018] The present invention first proposes a combined strategy for dynamically adjusting the melt temperature and drawing speed in the isodiametric stage. This dynamic adjustment can significantly reduce the number of wide face defects, improve the surface quality of the crystal, and has higher flexibility and pertinence. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the fluctuation range of the single-crystal diameter with length in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present invention will be described in detail below with reference to the drawings and embodiments. The embodiments cited are only used to explain the present invention and are not used to limit the scope of the present invention.

[0021] The implementation process of the method of the present invention includes the following steps:

[0022] (1) Manually control the actual diameter size in the early stage of isodiametric growth to meet the target diameter size. Wait until the drawing speed change trend in the early stage of isodiametric growth approaches the growth setting, the single-crystal diameter change tends to be stable, check that the diameter measurement system signal is normal, calibrate the single-crystal furnace diameter measurement signal, and enable automatic diameter control.

[0023] (2) After the isodiametric diameter is stable, obtain the crystal positions at the stable positions A, B, and C of the diameter during the isodiametric process in sequence through the single-crystal furnace client, record the change range of the single-crystal diameter per rotation of the crystal at each position, obtain the maximum diameter and the minimum diameter, and calculate the differences ΔA1, ΔA2, and ΔA3 between the maximum diameter and the minimum diameter. Specifically, when operating, set the crystal rotation speed R (rotations per minute), record the diameter values at each position within 60 / R time, capture the diameter signal every 1 second, record the change range of the single-crystal diameter per rotation of the crystal, obtain the maximum diameter and the minimum diameter, and calculate the difference between the two.

[0024] (3) Calculate the diameter change rate α = (ΔA2 - ΔA1) / Δd (B-A) , β = (ΔA3 - ΔA2) / Δd (C-B) , where Δd (B-A)is the length from position B to position A, Δd (C-B) is the length from position C to position B; compare the values of α and β;

[0025] If α ≥ β, it indicates that the wide face has a tendency to decrease or no longer increase, then maintain the existing pulling speed to continue growing the single crystal;

[0026] If α < β, it indicates that the wide face has a tendency to increase; adjust the melt temperature from T1 to T2 (T2 < T1), and at the same time adjust the pulling speed from V1 to V2 (V2 < V1) until α ≥ β.

[0027] (4) As the length of the single crystal increases, repeat steps (1) and (2), continuously compare the change rate values of the diameters of two consecutive segments with respect to the length, adjust the temperature and pulling speed in a timely manner, and control the diameter difference of one rotation of the single crystal within the range of less than 1 mm during the isodiameter process, basically achieving the stability of the wide face of the single crystal growth.

[0028] Example 1

[0029] Use the method of the present invention to conduct experiments on the wide face growth of multiple silicon single crystals with a crystal orientation of <111> and a diameter of 158 mm (6 inches).

[0030] Set the isodiameter control diameter to 158 mm, and set the crystal rotation speed to 12 (cycles / minute), that is, the single crystal rotates one cycle every 5 seconds.

[0031] Take the isodiameter position A as 600 mm, and record the maximum diameter of one rotation of the isodiameter at this time as 158 mm and the minimum diameter as 155 mm. That is, at the position of 600 mm, the diameter difference is 3 mm.

[0032] Take the isodiameter position B as 605 mm, and record the maximum diameter of one rotation of the isodiameter at this time as 158 mm and the minimum diameter as 154 mm. That is, at the position of 605 mm, the diameter difference is 4 mm.

[0033] Take the isodiameter position C as 610 mm, and record the maximum diameter of one rotation of the isodiameter at this time as 158 mm and the minimum diameter as 152 mm. That is, at the position of 610 mm, the diameter difference is 6 mm.

[0034] Calculate the change rate α of the diameter of the wide face of the single crystal within the length from 600 mm to 605 mm, α = (4 - 3) / 5 = 0.2. Calculate the change rate β of the diameter of the wide face of the single crystal within the length from 605 mm to 610 mm, β = (6 - 4) / 5 = 0.4.

[0035] Compare the values of α and β, α < β, which indicates that the wide face of the single crystal has a tendency to increase. Manually correct the temperature by 3 sp / hr and increase the pulling speed by 4 mm / hr.

[0036] Take the equal-diameter position D as 740 mm, and record the maximum diameter of 158 mm and the minimum diameter of 156 mm when the equal-diameter rotates one week at this time. That is, at the position of 740 mm, the diameter difference is 2 mm.

[0037] Take the equal-diameter position E as 745 mm, and record the maximum diameter of 158 mm and the minimum diameter of 156 mm when the equal-diameter rotates one week at this time. That is, at the position of 745 mm, the diameter difference is 2 mm.

[0038] Take the equal-diameter position F as 750 mm, and record the maximum diameter of 158 mm and the minimum diameter of 157 mm when the equal-diameter rotates one week at this time. That is, at the position of 750 mm, the diameter difference is 1 mm.

[0039] Calculate the change rate α of the single-crystal wide-face diameter within the length from 740 mm to 745 mm, α = (2 - 2) / 5 = 0, that is, the wide face does not change. Calculate the change rate β of the single-crystal wide-face diameter within the length from 745 mm to 750 mm, β = (1 - 2) / 5 = -0.2.

[0040] Compare the values of α and β. Since α > β, it indicates that the tendency of the single-crystal wide face to increase is suppressed, and it also indicates that the wide face begins to develop in the decreasing direction.

[0041] Repeat the above steps, and keep α ≥ β. The fluctuation range of the single-crystal diameter with the length is as Figure 1 shown.

[0042] The present invention first proposes a combined strategy for dynamically adjusting the melt temperature and pulling speed in the equal-diameter stage. Through experimental verification, this dynamic adjustment can control the diameter difference caused by the wide face when the single crystal rotates one week within a certain range, and basically can achieve the stability of the wide face of the single-crystal growth, thereby significantly reducing the number of wide-face defects and improving the crystal surface quality. In the prior art, fixed process parameters are usually adopted, which are difficult to adapt to the complex changes in crystal growth in the equal-diameter stage, while the dynamic optimization strategy of the present invention has higher flexibility and pertinence.

Claims

1. A method for controlling the wide - face stability of <111> - oriented single - crystal silicon in the isodiametric stage, comprising the following steps: (1) After the isodiametric diameter is stabilized, sequentially record the change range of the single - crystal diameter per revolution at crystal positions A, B, and C at the diameter - stable position through the single - crystal furnace client, and calculate the differences ΔA1, ΔA2, and ΔA3 between the maximum diameter and the minimum diameter; (2) Calculate the diameter change rate α = (ΔA2 - ΔA1) / Δd (B-A) , β = (ΔA3 - ΔA2) / Δd (C-B) , where Δd (B-A) is the length from position B to position A, and Δd (C-B) is the length from position C to position B; compare the values of α and β; If α ≥ β, continue to grow the single - crystal at the existing pulling speed; If α < β, reduce the melt temperature from T1 to T2, and at the same time reduce the pulling speed from V1 to V2 until α ≥ β; (3) Repeat steps (1) and (2) to control the diameter difference per revolution of the single - crystal to be less than 2 mm.

2. The control method for the wide surface stability in the equal-diameter stage of <111> crystal orientation single-crystalline silicon according to claim 1, wherein Δd (B-A) is equal to Δd (C-B) .

3. The control method for the wide surface stability in the equal-diameter stage of <111> crystal orientation single-crystalline silicon according to claim 1 or 2, characterized in that, Δd (B-A) and Δd (C-B) are 4 - 8 mm respectively.

4. The control method for the wide surface stability in the equal diameter stage of <111> crystal orientation single crystal silicon according to claim 3, wherein, Δd (B-A) and Δd (C-B) are 5 mm respectively.

5. The method for controlling the stability of the wide surface in the equal-diameter stage of <111> crystal orientation single-crystalline silicon according to claim 1 or 2, characterized in that, In the early stage of isodiametric growth, manually control the actual diameter in the early stage of isodiametric growth to meet the target diameter size. When the pulling - speed change trend in the early stage of isodiametric growth approaches the growth setting and the single - crystal diameter change tends to be stable, check that the signal of the diameter - measuring system is normal, calibrate the single - crystal furnace diameter - measuring signal, and enable automatic diameter control.

6. The control method for the wide surface stability in the isodiameter stage of <111> crystal orientation single crystal silicon according to claim 1 or 2, characterized in that, In the step (1), the diameter signal capture frequency is 1 time per second.

7. The method for controlling the stability of the wide surface in the equal-diameter stage of <111> crystal orientation single-crystalline silicon according to claim 1 or 2, characterized in that, In the step (2), the adjustment range of the melt temperature T is 3 - 5 sp / hr, and the adjustment range of the pulling speed V is 3 - 5 mm / hr.

8. The method for controlling the wide surface stability in the isodiametric stage of <111> crystal orientation single crystal silicon according to claim 1 or 2, characterized in that, In the step (3), control the diameter difference per revolution of the single - crystal to be less than 1 mm.

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