High-efficiency and high-quality crystal pulling method

Abstract

The invention relates to the technical field of semiconductors, in particular to an efficient and high-quality crystal pulling method which comprises the steps of feeding, welding, seeding, shouldering, equal diameter and ending. Wherein in the charging step, raw materials are added into a crucible, the raw materials comprise a silicon material, a phosphorus alloy and an antimony elementary substance, and the mass ratio of the phosphorus alloy to the antimony elementary substance is 1: (1.1-1.5). According to the crystal pulling method, the resistance centrality of the prepared crystal bar can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a high-efficiency and high-quality crystal pulling method. Background Art

[0002] The Czochralski method is a commonly used method for preparing single crystal silicon. This method places polycrystalline silicon material in a quartz crucible for melting. In the Czochralski single crystal process, the seed crystal and the melt are first brought into contact, so that the molten silicon at the solid-liquid interface cools and crystallizes along the seed crystal, and grows by slowly pulling out the seed crystal. After the necking is completed, the crystal growth diameter is enlarged by reducing the pulling speed and / or the melt temperature until the target diameter is reached; after the shoulder is released, the crystal growth enters the equal-diameter growth stage by controlling the pulling speed and the melt temperature; finally, the diameter of the crystal growth surface is gradually reduced by increasing the pulling speed and raising the melt temperature to form a tail cone, until the crystal finally leaves the melt surface, and the growth of the single crystal silicon rod is completed.

[0003] However, the resistance concentration of the crystal rod obtained by the straightening method provided by the related art is poor. Summary of the invention

[0004] The object of the present invention is to provide an efficient and high-quality crystal pulling method, which can effectively improve the resistance concentration of the obtained crystal rod.

[0005] The present invention is achieved in that:

[0006] The present invention provides an efficient and high-quality crystal pulling method, including: feeding, welding, seeding, shouldering, equal diameter, and finishing; wherein,

[0007] In the step of adding materials, raw materials are added to the crucible, the raw materials include silicon material, phosphorus alloy and antimony element, and the mass ratio of phosphorus alloy to antimony element is 1:(1.1-1.5).

[0008] In an optional embodiment, the feeding includes a first feeding and a second feeding, and the mass ratio of phosphorus alloy and antimony element added in at least one of the first feeding step and the second feeding step is 1:(1.1-1.5).

[0009] In an optional embodiment, in the feeding step, the crucible rotation speed is 0.5rpm~1rpm, the main heater power is 60kw~70kw, the bottom heater power is 120kw~130kw, the crystal rotation speed is less than or equal to 0.5rpm; the protective gas argon flow rate is 140slpm~150slpm.

[0010] In an optional embodiment, in the welding step, the crucible rotation speed is 8-10 rpm, the crystal rotation speed is 8-10 rpm, the argon gas flow rate is 60-80 slpm, and the furnace pressure is 8-10 Torr.

[0011] In an optional embodiment, in the seeding step, the crucible rotation speed is 8-10 rpm, the crystal rotation speed is 8-10 rpm, the argon gas flow rate is 60-80 slpm, and the furnace pressure is 8-10 Torr.

[0012] In an alternative embodiment, the crucible rotation speed during the shouldering step is linearly reduced.

[0013] In an optional embodiment, the shoulder release time is 2 to 2.8 hours, and in the shoulder release step, the crucible rotation speed is linearly reduced from 8 to 10 rpm to 3.5 to 4.5 rpm, the crystal rotation speed is 8 to 10 rpm, the argon flow rate is 60 to 80 slpm, and the furnace pressure is reduced from 8 to 10 Torr to 4 to 5 Torr.

[0014] In an optional embodiment, in the equal-diameter process, during the process of forming the head of the crystal rod, the crucible rotation speed is increased from 3.5-4.5 rpm to 6-7 rpm; during the process of forming the tail of the crystal rod, the crucible rotation speed is reduced from 6-7 rpm to 3.5-4.5 rpm, the crystal rotation speed is 8-10 rpm, the argon flow rate is increased from 60-80 slpm to 100-120 slpm, and the furnace pressure is 4-5 Torr.

[0015] In an optional embodiment, the length of the head is less than or equal to 600 mm.

[0016] In an optional embodiment, the length of the tail is 800-1000 mm.

[0017] The high-efficiency and high-quality crystal pulling method of the present invention includes the following beneficial effects:

[0018] The preparation method of the present invention controls the mass ratio of phosphorus alloy and antimony element to be 1:(1.1-1.5) during the addition of materials, and can accurately adjust the electrical properties of silicon crystal to improve the resistance concentration of the obtained crystal rod; wherein phosphorus is a donor impurity and can provide free electrons, while the doping efficiency of antimony is slightly lower than that of phosphorus, but its segregation coefficient in silicon is small and can be more evenly distributed during the crystal growth process. By adjusting the ratio of the two, the antimony element is appropriately increased compared to the phosphorus alloy, so that the doping concentration can be balanced, the resistivity fluctuation can be reduced, and the resistance concentration can be improved, thereby ensuring that the electrical properties of the single crystal silicon are more uniform and stable. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0020] The present disclosure provides an efficient and high-quality crystal pulling method, which belongs to a straightening method, comprising:

[0021] Vacuuming process → leak detection process → melting process → feeding process → welding process → seeding process → shoulder release process → equal diameter process → finishing process → (circular rod pulling process) → furnace stopping process.

[0022] Among them, in the feeding process step, the added raw materials include silicon material, phosphorus alloy and antimony element, and the mass ratio of phosphorus alloy to antimony element is 1:(1.1~1.5), for example: 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc., which is not specifically limited here.

[0023] When adding materials, the mass ratio of phosphorus alloy and antimony is controlled to be 1:(1.1~1.5), which can accurately adjust the electrical properties of silicon crystal to improve the resistance concentration of the obtained crystal rod; among them, phosphorus is a donor impurity that can provide free electrons, while the doping efficiency of antimony is slightly lower than that of phosphorus, but its segregation coefficient in silicon is small, and it can be more evenly distributed during the crystal growth process. By adjusting the ratio of the two, compared with the phosphorus alloy, the appropriate increase of antimony can balance the doping concentration and reduce resistivity fluctuations, thereby improving resistance concentration and ensuring that the electrical properties of single crystal silicon are more uniform and stable.

[0024] Furthermore, the above-mentioned feeding includes the initial feeding during crystal pulling and the secondary feeding in the subsequent cyclic rod pulling process. Both the initial feeding and the secondary feeding are carried out according to the mass ratio of phosphorus alloy to antimony element of 1: (1.1~1.5) to ensure that the single crystal silicon rods produced can improve the resistance concentration.

[0025] Of course, in other embodiments, the materials may be added only for the first time or only for the second time at a mass ratio of 1:(1.1-1.5) between the phosphorus alloy and the antimony element.

[0026] It should be noted that, during crystal pulling, the amount of silicon material added can be determined by looking up a table (eg, a doping table for the target resistivity of the head) as needed, and is not specifically limited here.

[0027] It should also be noted that in the cyclic rod drawing process, silicon material needs to be added for the second time, and the amount of silicon material added is determined according to the difference between the original amount added and the amount remaining in the crucible.

[0028] Optionally, the phosphorus alloys include but are not limited to: red phosphorus, silicon phosphide, boron phosphide, gallium phosphide and aluminum phosphide.

[0029] Optionally, in the process step of adding materials, the rotation speed of the crucible is 0.5rpm~1rpm (for example: 0.5rpm, 0.6rpm, 0.7rpm, 0.8rpm, 0.9rpm, 1rpm, etc., not specifically limited here), the power of the main heater is 60kw~70kw (for example: 60kw, 62kw, 65kw, 67kw, 70kw, etc., not specifically limited here), and the power of the bottom heater is 120kw~130kw (for example: 120kw, 123kw , 126kw, 128kw, 130kw, etc., not specifically limited here), the crystal rotation speed is less than or equal to 0.5rpm (for example: 0.5rpm, 0.4rpm, 0.3rpm, 0.2rpm, 0.1rpm, etc., not specifically limited here); the flow rate of protective gas argon is 140slpm~150slpm (for example: 140slpm, 142slpm, 145slpm, 147slpm, 150slpm, etc., not specifically limited here). In this way, by optimizing the rotation speed of the crucible, the uniformity of the distribution of the molten silicon material in the crucible can be improved, and the uniform melting and mixing of the silicon material and the dopant can be promoted. By optimizing the power of the main heater and the bottom heater so that the power of the bottom heater is greater than that of the main heater, it can be ensured that the silicon material is melted uniformly from the bottom to the surface, and the unmelted or over-melted areas can be reduced. At the same time, the temperature gradient in the melt can be reduced, and thermal stress can be reduced, which is beneficial to reducing defects generated during the crystal growth process. At the same time, optimizing the crucible rotation speed and the power of the main heater and the bottom heater can speed up the melting rate, improve the feeding efficiency, and save work time.

[0030] It should be noted that the arrangement positions of the main heater and the bottom heater are similar to those in the crystal pulling equipment provided in the related art, and will not be repeated here.

[0031] Optionally, in the welding process steps, the crucible rotation speed is 8 to 10 rpm (for example: 8 rpm, 9 rpm, 10 rpm, etc., not specifically limited herein), the crystal rotation speed is 8 to 10 rpm (for example: 8 rpm, 9 rpm, 10 rpm, etc., not specifically limited herein), the argon flow rate is 60 to 80 slpm (for example: 60 slpm, 63 slpm, 65 slpm, 68 slpm, 70 slpm, 73 slpm, 76 slpm, 80 slpm, etc., not specifically limited herein), and the furnace pressure is 8 to 10 Torr (for example: 8 Torr, 9 Torr, 10 Torr, etc., not specifically limited herein). In this way, optimizing the crucible rotation speed can throw impurities in the crucible to the edge of the crucible, improve the survival rate of the lead-in, thereby improving the crystal formation rate and the yield rate; at the same time, optimizing the crystal rotation speed can ensure the uniform distribution of doped phosphorus and antimony, and then ensure the consistency of the doping concentration in the obtained crystal rod, improve the uniformity of electrical properties, and at the optimized crystal rotation speed, it can also reduce the temperature gradient on the crystal surface, improve the problem of local overheating or overcooling of the crystal, and then reduce the thermal stress and defects generated during the crystal growth process. At the same time, it can also ensure the symmetry and stability of crystal growth to further improve the quality of the grown crystal.

[0032] Optionally, in the crystal seeding step, the crucible rotation speed is 8 to 10 rpm (for example: 8 rpm, 9 rpm, 10 rpm, etc., not specifically limited herein), the crystal rotation speed is 8 to 10 rpm (for example: 8 rpm, 9 rpm, 10 rpm, etc., not specifically limited herein), the argon flow rate is 60 to 80 slpm (for example: 60 slpm, 63 slpm, 65 slpm, 68 slpm, 70 slpm, 73 slpm, 76 slpm, 80 slpm, etc., not specifically limited herein), and the furnace pressure is 8 to 10 Torr (for example: 8 Torr, 9 Torr, 10 Torr, etc., not specifically limited herein). Similar to the welding process, optimizing the crucible rotation speed can throw impurities in the crucible to the edge of the crucible, thereby improving the survival rate of the lead-in, thereby improving the crystal formation rate and the yield rate; at the same time, optimizing the crystal rotation speed can ensure the uniform distribution of doped phosphorus and antimony, and then ensure the consistency of the doping concentration in the obtained crystal rod, improve the uniformity of electrical properties, and at the optimized crystal rotation speed, it can also reduce the temperature gradient on the crystal surface, improve the problem of local overheating or overcooling of the crystal, and then reduce the thermal stress and defects generated during the crystal growth process. At the same time, it can also ensure the symmetry and stability of crystal growth to further improve the quality of the grown crystal.

[0033] Optionally, the crucible rotation speed in the shoulder release step decreases linearly. Compared with the processes of welding and seeding, the linearly decreasing crucible rotation speed during shoulder release is conducive to reducing the head oxygen content of the crystal rod (i.e., the oxygen content of the head of the single crystal silicon rod, i.e., the oxygen content of the starting part of crystal growth), thereby improving the quality of the obtained crystal rod.

[0034] Furthermore, the total duration of the shoulder release step is controlled at 2 to 2.8 hours, during which the crucible rotation speed is linearly reduced from 8 to 10 rpm to 3.5 to 4.5 rpm (for example, 8 rpm is reduced to 3.5 rpm, 8 rpm is reduced to 3.7 rpm, 9 rpm is reduced to 3.9 rpm, 10 rpm is reduced to 4.3 rpm, 8.8 rpm is reduced to 4.5 rpm, etc., not specifically limited here), the crystal rotation speed is 8 to 10 rpm (for example, 8 rpm, 9 rpm, 10 rpm, etc., not specifically limited here), and the argon gas flow rate is 60 The furnace pressure is reduced from 8-10 Torr to 4-5 Torr (for example: 8 Torr to 4 Torr, 9 Torr to 4.2 Torr, 10 Torr to 4.4 Torr, 8.5 Torr to 4.7 Torr, 9.2 Torr to 5 Torr, etc., not specifically limited here). In the process of shouldering, the crucible speed is gradually reduced, and the furnace pressure is also reduced, which can more effectively reduce the head oxygen content, improve the crystal quality, and minimize the volatilization rate of antimony element, thereby more effectively improving the resistance concentration.

[0035] Optionally, in the process of forming the head of the crystal rod, the crucible rotation speed is increased from 3.5 to 4.5 rpm to 6 to 7 rpm (for example, 3.5 rpm to 6 rpm, 3.8 rpm to 6.3 rpm, 4 rpm to 6.5 rpm, 4.2 rpm to 6.8 rpm, 4.5 rpm to 7 rpm, etc., which are not specifically limited here), that is, the crucible rotation speed changes linearly based on the length of the crystal rod head; in the process of forming the tail of the crystal rod, the crucible rotation speed is reduced from 6 to 7 rpm to 3.5 to 4.5 rpm (for example, 6 rpm to 3.5 rpm, 6.2 rpm to 3.7 rpm, 6.5 rpm to 3.9 rpm, 6.8 rpm to 4.3 rpm, 7 rpm to 4.5 rpm, etc., which are not specifically limited here The crucible rotation speed varies linearly based on the length of the crystal rod tail, the crystal rotation speed is 8-10rpm (for example, 8rpm, 9rpm, 10rpm, etc., not specifically limited here), and the argon flow rate is increased from 60-80slpm to 100-120slpm (for example, 60slpm to 100slpm, 63slpm to 105slpm, 65slpm to 110slpm, 70slpm to 115slpm, 80slpm to 120slpm, etc., not specifically limited here), that is, the argon flow rate varies linearly based on the length of the crystal rod tail, and the furnace pressure is 4-5Torr (for example, 4Torr, 4.2Torr, 4.4Torr, 4.7Torr, 5Torr, etc., not specifically limited here). In this way, adapting different crucible rotation speeds at the head and tail of the crystal rod can increase the survival rate of the crystal rod head and reduce the oxygen content in the tail, thereby improving the crystallization rate and the finished product while reducing the oxygen content in the tail.

[0036] It should be noted that in the process of forming the head of the crystal rod in the equal diameter process, no process parameters that need to be changed are mentioned, and all are performed with reference to the shoulder release process.

[0037] Optionally, the length of the head is less than or equal to 600 mm, that is, the length of the crystal rod from the beginning of growth to the length less than or equal to 600 mm is the head of the crystal rod.

[0038] Optionally, the length of the tail is 800-1000 mm, that is, when a crystal rod of a set length is grown, the last grown 800-1000 mm is the tail of the crystal rod.

[0039] The present invention is further described in detail below in conjunction with embodiments.

[0040] Example 1

[0041] The crystal rod is prepared according to the following steps:

[0042] Vacuuming process → leak detection process → melting process → feeding process → welding process → seeding process → shoulder release process → equal diameter process → finishing process → furnace stopping process.

[0043] The process parameters and the test results of the resistivity, head oxygen content and tail oxygen content of the crystal rod are shown in Table 1-1.

[0044] The process parameters of Example 2 and Example 3, and Comparative Examples 1-12, and the test results of the resistivity, head oxygen content, and tail oxygen content of the crystal rod are shown in Table 1-1 and Table 1-2; among them, the process parameters not recorded in Example 2 and Example 3, and Comparative Examples 1-12 refer to the process parameters of Example 1, the resistivity is detected by the Hall effect method, and the head oxygen content and tail oxygen content are detected by Fourier transform infrared spectroscopy.

[0045] Table 1-1

[0046]

[0047]

[0048] Table 1-2

[0049]

[0050]

[0051] According to Table 1-1 and Table 1-2, by comparing Examples 1-3 and Comparative Examples 1 and 2, it can be seen that optimizing the mass ratio of phosphorus alloy and antimony element can ensure the uniformity of distribution of phosphorus and antimony in the crystal rod, effectively optimize the resistivity of the crystal rod, ensure resistivity concentration, and at the same time reduce the head oxygen content and tail oxygen content to improve the yield rate of the crystal rod.

[0052] By comparing Examples 1-3 and Comparative Examples 3 and 4, it can be seen that when the crucible rotation speed in the feeding step is low, even if the power of the main heater and the bottom heater is increased, the resistivity ratio of the obtained crystal rod decreases, the yield rate decreases, and the head oxygen content and the tail oxygen content are both high; and when the crucible rotation speed in the feeding step is too high, it is still impossible to ensure that the resistivity ratio, yield rate, head oxygen content and tail oxygen content of the crystal rod are optimized.

[0053] By comparing Examples 1-3 with Comparative Examples 5 and 6, it can be seen that in the steps of welding and seeding, no matter the crucible rotation speed is too large or too small, it is difficult to ensure a reliable temperature gradient, the yield rate of the crystal rod cannot be improved, the head oxygen content and the tail oxygen content cannot be reduced, the doped phosphorus and antimony cannot be evenly distributed, and thus the resistivity ratio cannot be increased.

[0054] By comparing Examples 1-3 with Comparative Examples 7 and 8, it can be seen that in the shoulder release step, whether the crucible rotation speed and the furnace pressure are not reduced, or the crucible rotation speed and the furnace pressure are increased, the volatilization of the antimony element is uncontrollable, and it is difficult to increase the resistivity ratio of the crystal rod (0.8 to 1.3Ω·cm), that is, to improve the resistance concentration, the yield is low, and the head oxygen content and the tail oxygen content are both high.

[0055] By comparing Examples 1-3 and Comparative Example 9, it can be seen that in the equal diameter step, the crucible rotation when forming the crystal rod head is reduced, and when forming the crystal rod tail, the crucible rotation is increased, and the argon gas flow rate is low, and the head oxygen content and the tail oxygen content are significantly increased, especially the tail oxygen content increases significantly; at the same time, the resistivity ratio and the yield rate are reduced.

[0056] By comparing Examples 1-3 and Comparative Example 10, it can be seen that in the equal diameter step, when forming the head of the crystal rod, the crucible rotates too much, and the oxygen content of the head increases significantly, while when forming the tail of the crystal rod, the crucible rotates too little and the argon gas flow rate is too large, and the increase in the oxygen content of the tail is also quite significant; at the same time, the resistivity ratio and the yield rate are reduced.

[0057] By comparing Examples 1-3 and Comparative Examples 11 and 12, it can be seen that in the solution in which the crystal pulling method of the present disclosure is not followed at all, the doping effect of phosphorus and antimony is poor, and it is obviously difficult to improve the resistance concentration.

[0058] In summary, the single crystal silicon ingot produced by the preparation method of the present invention has a high crystallization rate, a high yield rate, a low head oxygen content and a tail oxygen content, and can improve resistance concentration.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An efficient and high-quality crystal pulling method, characterized in that: include: Feeding, welding, seeding, shouldering, equal diameter, and finishing; among them, In the step of adding materials, the added raw materials include silicon material, phosphorus alloy and antimony element, and the mass ratio of the phosphorus alloy to the antimony element is 1:(1.1-1.5).

2. The high-efficiency and high-quality crystal pulling method according to claim 1, characterized in that: The adding includes a primary adding and a secondary adding, and the mass ratio of the phosphorus alloy to the antimony element added in at least one of the primary adding and the secondary adding is 1:(1.1-1.5).

3. The high-efficiency and high-quality crystal pulling method according to claim 1, characterized in that: In the step of adding materials, the crucible has a rotation speed of 0.5 rpm to 1 rpm, the main heater has a power of 60 kW to 70 kW, the bottom heater has a power of 120 kW to 130 kW, the crystal rotation speed is less than or equal to 0.5 rpm, and the protective gas argon flow rate is 140 slpm to 150 slpm.

4. The high-efficiency and high-quality crystal pulling method according to claim 1, characterized in that: In the welding step, the crucible rotation speed is 8-10 rpm, the crystal rotation speed is 8-10 rpm, the argon gas flow rate is 60-80 slpm, and the furnace pressure is 8-10 Torr.

5. The high-efficiency and high-quality crystal pulling method according to claim 1, characterized in that: In the step of seeding, the crucible rotation speed is 8-10 rpm, the crystal rotation speed is 8-10 rpm, the argon gas flow rate is 60-80 slpm, and the furnace pressure is 8-10 Torr.

6. The high-efficiency and high-quality crystal pulling method according to claim 5, characterized in that: The crucible rotation speed in the shoulder release step is linearly reduced.

7. The high-efficiency and high-quality crystal pulling method according to claim 6, characterized in that: The shoulder release time is 2 to 2.8 hours, and in the shoulder release step, the crucible rotation speed is linearly reduced from 8 to 10 rpm to 3.5 to 4.5 rpm, the crystal rotation speed is 8 to 10 rpm, the argon flow rate is 60 to 80 slpm, and the furnace pressure is reduced from 8 to 10 Torr to 4 to 5 Torr.

8. The high-efficiency and high-quality crystal pulling method according to claim 1, characterized in that: In the equal-diameter process, during the process of forming the head of the crystal rod, the crucible rotation speed is increased from 3.5-4.5rpm to 6-7rpm; during the process of forming the tail of the crystal rod, the crucible rotation speed is reduced from 6-7rpm to 3.5-4.5rpm, the crystal rotation speed is 8-10rpm, the argon flow rate is increased from 60-80slpm to 100-120slpm, and the furnace pressure is 4-5Torr.

9. The high-efficiency and high-quality crystal pulling method according to claim 8, characterized in that: The length of the head is less than or equal to 600 mm.

10. The high-efficiency and high-quality crystal pulling method according to claim 8, characterized in that: The length of the tail is 800-1000 mm.

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