Growth method for excluding seeding dislocations of single crystal silicon and crystal pulling method for single crystal ingot

Abstract

The application provides a growth method for excluding single crystal silicon seeding dislocation, and belongs to the technical field of single crystal silicon seeding methods. The seeding process is sequentially divided into a necking section and a thin neck section, and the seeding process is controlled by sectional double PID control, so that the necking section and the thin neck section are controlled by corresponding PID control, the necking section can quickly reduce the diameter, the target diameter 5.5 mm is reached, the thin neck section can stably maintain the target diameter, and when the crystal enters the shoulder stage, the dislocation density at the solid-liquid interface is reduced to the theoretical minimum level. Therefore, the NG phenomena such as crystal strain, polycrystallization or edge breakage caused by dislocation inheritance in the shoulder process are fundamentally suppressed. The NG rate in the shoulder process is significantly reduced, thereby greatly saving the material cost and time cost consumed by remelting, reinstallation and repeated seeding caused by shoulder failure, and effectively improving the single-furnace output rate and overall production efficiency of the Czochralski silicon single crystal furnace.

Description

Technical Field

[0001] This invention relates to the field of monocrystalline silicon seeding methods, specifically to a growth method for eliminating seeding dislocations in monocrystalline silicon and a crystal pulling method for monocrystalline rods. Background Technology

[0002] The Czochralski method (CZ method) is currently the mainstream method for producing silicon single crystals, accounting for approximately 70% to 80% of the world's silicon single crystal production. The basic process flow for growing silicon single crystals using the Czochralski method includes: feeding → melting → necking growth → shoulder growth → constant diameter growth → tail growth. Among these, necking (also known as crystal pulling or thinning) is one of the key steps determining whether dislocation-free crystal growth can be achieved.

[0003] In the Czochralski method for growing silicon single crystals, when the seed crystal is immersed in the high-temperature silicon melt, the large temperature difference between the seed crystal and the melt causes thermal shock, generating a large number of slip dislocations in the seed crystal. To eliminate these dislocations, the industry commonly uses the Dash necking technique (also known as the Dash necking method): the seed crystal is rapidly pulled upwards, reducing the diameter of the grown crystal to a certain size. Since the dislocation lines form a certain angle with the crystal growth axis, as long as the necking length is sufficient, the dislocations can extend to the crystal surface and be eliminated, thus achieving the growth of a zero-dislocation crystal. After necking growth is completed, the crystal enters the thin-diameter section and the shoulder section. The thin-diameter section is the transition region connecting the necking and shoulder formation, and its precise diameter control has a decisive impact on the success rate of subsequent shoulder formation. Currently, the control of the diameter of the seed crystal section in existing technologies mainly relies on the operator's experience and traditional pulling speed-temperature control methods. However, due to the characteristics of strong coupling, large hysteresis, and multivariate interference in the Czochralski crystal growth process, it is difficult to guarantee the diameter control accuracy of the narrow section, resulting in a high NG (non-conforming) rate of shoulder formation, which seriously affects the yield and production efficiency of single crystal growth. Summary of the Invention

[0004] In view of this, the present invention provides a growth method for eliminating single-crystal silicon seed dislocations to reduce the shoulder formation failure rate.

[0005] It is also necessary to provide a method for pulling single-crystal rods.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A growth method for eliminating dislocations in monocrystalline silicon crystals involves dividing the crystal pulling process into a necking section and a thinning section. The crystal pulling process is controlled by segmented dual PID control, so that the necking section and the thinning section are controlled by corresponding PID controls. In this way, the necking section can quickly shrink to the target diameter, and the thinning section can stably maintain the target diameter, thus avoiding shoulder formation and NG (non-compliance).

[0008] The target diameter is 5.5 mm.

[0009] Preferably, it includes the following steps:

[0010] S1: Set the proportional coefficient P1, integral coefficient I1, and derivative coefficient D1 for the PID control of the necking section, the proportional coefficient P2, integral coefficient I2, and derivative coefficient D2 for the PID control of the necking section, as well as the crystal-drawing parameters and the diameter settings for the necking and necking sections.

[0011] S2: Pull the seed crystal to generate the crystal. Control the crystal generation according to the set PID coefficients of the necking section and the fine necking section so that the actual diameter of the necking section and the fine necking section is equal to the set diameter value.

[0012] Preferably, the proportional coefficient P1 of the PID control in the necking section is 4.0-6.0;

[0013] The integral coefficient I1 of the PID control for the necking section is 0.08-0.12;

[0014] The differential coefficient D1 of the PID control in the necking section is 0.01-0.03;

[0015] The proportional coefficient P2 of the PID control in the narrow neck section is 0.8-1.5;

[0016] The integral coefficient I2 of the PID control for the narrow neck section is 0.01-0.03;

[0017] The differential coefficient D2 of the PID control in the narrow neck section is 0.05-0.08.

[0018] Preferably, the seeding parameters include at least one of seeding length and seeding speed.

[0019] The necking section is the starting point for drawing the lead crystal, and the length of the lead crystal is 80mm.

[0020] The necking section is from the point where the crystal puller reaches 80mm in length until the crystal puller ends.

[0021] Preferably, the diameter of the narrow neck section is set to 5.5 mm.

[0022] Preferably, in the necking section, when the lead length is 10mm, the diameter is set to 18mm, and when the lead length is 80mm, the diameter is set to 5.5mm.

[0023] Preferably, the upper limit of the diameter setting value of the thin neck segment is 6.5 mm and the lower limit is 3.5 mm.

[0024] Preferably, it is suitable for pulling 4-6 inch crystal rods.

[0025] Preferably, the neck of the 4-inch crystal ingot is 180mm long, the neck of the 5-inch crystal ingot is 180mm long, and the neck of the 6-inch crystal ingot is 250mm long.

[0026] A method for pulling a single-crystal rod, comprising the growth method described above for eliminating seed dislocations in single-crystal silicon.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a growth method for eliminating dislocations during crystal growth in single-crystal silicon. The crystal growth process is divided into a necking stage and a thinning stage. By employing segmented dual-PID control, the necking and thinning stages are controlled by their respective PID controllers. This allows the necking stage to rapidly shrink to the target diameter of 5.5 mm, while the thinning stage stably maintains the target diameter. This ensures that the dislocation density at the solid-liquid interface is reduced to the theoretical minimum when the crystal enters the shoulder formation stage. Therefore, no-go phenomena (NG) caused by dislocation inheritance during shoulder formation, such as crystal twinning, polycrystalline formation, or edge breakage, are fundamentally suppressed. The NG rate is significantly reduced during shoulder formation, thereby greatly saving material and time costs associated with remelting, reloading, and repeated crystal growth due to shoulder failure. This effectively improves the single-furnace yield and overall production efficiency of the Czochralski silicon single-crystal furnace. Attached Figure Description

[0029] Figure 1 The diagram shows the diameter control results for both the example and the comparative example.

[0030] Figure 2 The image shows the results of placing the shoulder in the example and comparative examples.

[0031] In the picture: Figure 1 Before optimization refers to the comparative example, and after optimization refers to the implementation example. Figure 2 The comparison example before improvement refers to the example after improvement. Detailed Implementation

[0032] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are also given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Please refer to Figure 1 A growth method for eliminating dislocations in monocrystalline silicon is proposed. The crystal pulling process is divided into a necking section and a thinning section. The crystal pulling process is controlled by segmented dual PID control so that the necking section and the thinning section are controlled by corresponding PID. In this way, the necking section can quickly shrink to the target diameter, and the thinning section can stably maintain the target diameter, thus avoiding shoulder formation and NG.

[0035] The target diameter is 5.5 mm.

[0036] This invention provides a growth method for eliminating dislocations during crystal growth in single-crystal silicon. The crystal growth process is divided into a necking stage and a thinning stage. By employing segmented dual-PID control, the necking and thinning stages are controlled by their respective PID controllers. This allows the necking stage to rapidly shrink to the target diameter of 5.5 mm, while the thinning stage stably maintains the target diameter. This ensures that the dislocation density at the solid-liquid interface is reduced to the theoretical minimum when the crystal enters the shoulder formation stage. Therefore, no-go phenomena (NG) caused by dislocation inheritance during shoulder formation, such as crystal twinning, polycrystalline formation, or edge breakage, are fundamentally suppressed. The NG rate is significantly reduced during shoulder formation, thereby greatly saving material and time costs associated with remelting, reloading, and repeated crystal growth due to shoulder failure. This effectively improves the single-furnace yield and overall production efficiency of the Czochralski silicon single-crystal furnace.

[0037] The segmented dual PID strategy employed in this invention decouples the control objectives of the necking and narrowing stages—the front stage prioritizes "fast adjustment and accurate control," while the rear stage prioritizes "stability and resistance to disturbances," thus improving batch consistency. This avoids the contradiction inherent in traditional processes where using a single set of PID parameters cannot simultaneously address the two growth states of the necking and narrowing stages.

[0038] Furthermore, this includes the following steps:

[0039] S1: Set the proportional coefficient P1, integral coefficient I1, and derivative coefficient D1 for the PID control of the necking section, the proportional coefficient P2, integral coefficient I2, and derivative coefficient D2 for the PID control of the necking section, as well as the crystal-drawing parameters and the diameter settings for the necking and necking sections.

[0040] S2: Pull the seed crystal to generate the crystal. Control the crystal generation according to the set PID coefficients of the necking section and the fine necking section so that the actual diameter of the necking section and the fine necking section is equal to the set diameter value.

[0041] Furthermore, the proportional coefficient P1 of the PID control in the necking section is 4.0-6.0; so as to quickly output a large pulling speed adjustment amount when diameter deviation occurs, thereby achieving rapid reduction of the seed crystal diameter.

[0042] The integral coefficient I1 of the PID control for the necking section is 0.08-0.12; this is to quickly eliminate steady-state diameter deviation and ensure that sufficient necking and error correction are completed within 80mm.

[0043] The derivative coefficient D1 of the PID control for the necking section is 0.01-0.03 to suppress violent oscillations without compromising the rapid adjustment capability; an excessively large derivative will weaken the rapid narrowing effect.

[0044] The proportional coefficient P2 of the PID control for the narrow neck section is 0.8-1.5; it only outputs a small adjustment to the pulling speed to avoid large oscillations in the diameter.

[0045] The integral coefficient I2 of the PID control in the narrow neck section is 0.01-0.03; this is to slowly eliminate small steady-state deviations and prevent them from accumulating and causing large-scale speed adjustment actions.

[0046] The differential coefficient D2 of the PID control for the narrow neck section is 0.05-0.08 to suppress minor fluctuations in the narrow diameter and stabilize the diameter curve.

[0047] Specifically, considering the severe thermal shock and sudden diameter change in the initial stage of the necking section, independent PID control parameters for the necking section are configured. These parameters prioritize rapid diameter reduction, using high-gain proportional action and appropriate integral / derivative action to ensure the crystal diameter responds quickly to the pulling speed and temperature control during the initial necking stage, precisely converging to the target diameter (e.g., 5.5mm) within an extremely short process window. This not only significantly reduces the processing time of the necking section but, more importantly, ensures the precise achievement of the diameter at the end of the necking, providing accurate geometric boundary conditions for the dislocation line to fully extend to the crystal surface within the necking section, thus fundamentally eliminating dislocation residue problems caused by insufficient necking. For the extremely sensitive diameter fluctuations of the fine necking section, independent PID control parameters for the fine necking section are configured. By enhancing the memory effect of the integral action and adjusting the anti-interference capability of the derivative action, the influence of external disturbances such as high-temperature melt convection and thermal field drift on the fine necking diameter is effectively suppressed.

[0048] Furthermore, the seeding parameters include at least one of seeding length and seeding speed.

[0049] The necking section is the starting point for drawing the lead crystal, and the length of the lead crystal is 80mm.

[0050] The necking section is from the point where the crystal puller reaches 80mm in length until the crystal puller ends.

[0051] Furthermore, the diameter of the narrow neck segment is set to 5.5 mm.

[0052] Furthermore, in the necking section, when the lead length is 10mm, the diameter is set to 18mm, and when the lead length is 80mm, the diameter is set to 5.5mm.

[0053] Furthermore, the upper limit of the diameter setting value of the thin neck segment is 6.5 mm, and the lower limit is 3.5 mm.

[0054] Furthermore, it is suitable for pulling 4-6 inch crystal rods.

[0055] Furthermore, the neck of the 4-inch crystal ingot is 180mm long, the neck of the 5-inch crystal ingot is 180mm long, and the neck of the 6-inch crystal ingot is 250mm long.

[0056] A method for pulling a single-crystal rod, comprising the growth method described above for eliminating seed dislocations in single-crystal silicon.

[0057] Example:

[0058] The PID control process during the 5-inch crystal ingot pulling process is shown in Table 1. The initial pulling speed is 1 mm / min, the target diameter is 5.5 mm, the length of the necking section is 80 mm, and the length of the thin neck section is 180 mm.

[0059] Table 1

[0060]

[0061] Comparative Example

[0062] The PID control process during the crystal pulling process is shown in Table 2, and the rest is the same as in Example 1.

[0063] Table 2

[0064]

[0065] like Figure 1 As shown in the examples and comparative examples, the diameter control results demonstrate that the diameter fluctuation controlled by the method of the present invention is significantly smaller than that of the comparative example. The diameter of the narrow section is maintained stably at 5.5 mm throughout the entire process, avoiding the problems of wire breakage when the diameter of the narrow section is <3.5 mm and dislocation residue when the diameter is >6.5 mm.

[0066] Shoulder-expansion tests were conducted using the embodiments and comparative examples, and the shoulder-expansion results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the NG rate of shoulder placement in the comparative example is 10.7%, and the NG rate of shoulder placement in the example is 8.4%. It can be seen that the NG rate of shoulder placement is reduced by ≥2.3%, the control is more stable, and the NG rate of shoulder placement is reduced.

[0067] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A growth method for eliminating seed dislocations in single-crystal silicon, characterized in that, The crystal pulling process is divided into a necking section and a necking section. The crystal pulling process is controlled by segmented dual PID control so that the necking section and the necking section are controlled by corresponding PID control. In this way, the necking section can quickly reduce the diameter to reach the target diameter, and the necking section can stably maintain the target diameter to avoid shoulder formation and NG. The target diameter is 5.5 mm.

2. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 1, characterized in that, Includes the following steps: S1: Set the proportional coefficient P1, integral coefficient I1, and derivative coefficient D1 for the PID control of the necking section, the proportional coefficient P2, integral coefficient I2, and derivative coefficient D2 for the PID control of the necking section, as well as the crystal-drawing parameters and the diameter settings for the necking and necking sections. S2: Pull the seed crystal to generate the crystal. Control the crystal generation according to the set PID coefficients of the necking section and the fine necking section so that the actual diameter of the necking section and the fine necking section is equal to the set diameter value.

3. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 2, characterized in that, The proportional coefficient P1 of the PID control in the necking section is 4.0-6.0; The integral coefficient I1 of the PID control for the necking section is 0.08-0.12; The differential coefficient D1 of the PID control in the necking section is 0.01-0.03; The proportional coefficient P2 of the PID control in the narrow neck section is 0.8-1.5; The integral coefficient I2 of the PID control for the narrow neck section is 0.01-0.03; The differential coefficient D2 of the PID control in the narrow neck section is 0.05-0.

08.

4. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 2, characterized in that, The seeding parameters include at least one of seeding length and seeding speed; The necking section is the starting point for drawing the lead crystal, and the length of the lead crystal is 80mm. The necking section is from the point where the crystal puller reaches 80mm in length until the crystal puller ends.

5. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 4, characterized in that, The diameter of the narrow neck section is set at 5.5 mm.

6. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 4, characterized in that, In the necking section, when the lead length is 10mm, the diameter is set to 18mm; when the lead length is 80mm, the diameter is set to 5.5mm.

7. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 5, characterized in that, The upper limit of the diameter setting value of the narrow neck section is 6.5 mm, and the lower limit is 3.5 mm.

8. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 4, characterized in that, Suitable for pulling 4-6 inch crystal rods.

9. The growth method for eliminating single-crystal silicon seed dislocations as described in claim 8, characterized in that, The neck of the 4-inch crystal ingot is 180mm long, the neck of the 5-inch crystal ingot is 180mm long, and the neck of the 6-inch crystal ingot is 250mm long.

10. A method for pulling a single-crystal rod, characterized in that, This includes the growth method for eliminating single-crystal silicon seed dislocations as described in any one of claims 1-9.

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