Preparation method of low-oxygen high-quality monocrystalline silicon and monocrystalline crystal bar

Abstract

The invention provides a preparation method of low-oxygen high-quality monocrystalline silicon and a monocrystalline crystal bar, and belongs to the technical field of monocrystalline silicon preparation.The preparation method comprises the following steps that S1, in the crystal pulling process, a heater is adjusted to rise to a preset distance, so that a heating area of the heater is located above the liquid level of silicon melt, and the oxygen content of monocrystalline silicon is reduced; and S2, in the rising process of the heater, applying a horizontal magnetic field, adjusting the central position of the magnetic field to be flush with the liquid level position, and controlling the magnetic field intensity to remain unchanged so as to inhibit liquid surface convection, enable the melt temperature to be uniformly distributed and improve the quality of the monocrystalline silicon, so that the quality of the monocrystalline silicon is ensured while the oxygen content of the monocrystalline silicon is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal silicon preparation, and in particular to a method for preparing low-oxygen high-quality single crystal silicon and a single crystal ingot. Background Art

[0002] In the field of semiconductor material preparation technology, monocrystalline silicon is an important material, widely used in integrated circuits, solar cells and other fields. Among them, the 12-inch monocrystalline silicon wafer is a high-performance semiconductor component. Its size refers to its diameter, which is usually 12 inches (about 300 mm). 12-inch monocrystalline silicon wafers have the advantages of large size, excellent area, and high conversion efficiency. They can improve the production efficiency from silicon wafers to battery cells and then to components. They are mainly used in the production of high-performance chips such as logic chips and memory chips. The oxygen content in monocrystalline silicon has an important influence on its electrical properties. A higher oxygen content will lead to the formation of impurity energy levels, thereby reducing the carrier mobility and electron migration length of the material, affecting the performance of the chip.

[0003] In the prior art, the Chinese invention with application number 202311399324.2 specifically discloses a 12-inch ultra-low oxygen crystal rod pulling method and a single crystal crystal rod. During the crystal pulling process, the furnace pressure is adjusted to accelerate the volatilization rate of SiO generated by the quartz crucible and the silicon melt, and the volatilized SiO is taken away with the argon flow rate to reduce the oxygen content in the single crystal furnace to reduce the probability of oxygen entering the crystal rod. The crystal rod and crucible speed are further adjusted to suppress the convection of the melt in the crucible to reduce the oxygen content in the crystal rod, so that the oxygen content in the crystal rod is reduced. Although this patent reduces the oxygen content in the crystal rod, the quality of the crystal rod has not been well improved. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing low-oxygen high-quality single crystal silicon and a single crystal ingot to solve the technical problem of low quality of existing low-oxygen single crystal silicon.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for preparing low-oxygen high-quality single crystal silicon comprises the following steps: S1. During the crystal pulling process, adjusting the heater to rise to a predetermined distance so that the heating zone of the heater is located above the liquid surface of the silicon melt to reduce the oxygen content of the single crystal silicon; S2. During the rising process of the heater, a horizontal magnetic field is applied, the center position of the magnetic field is adjusted to be level with the liquid surface, and the magnetic field strength is controlled to remain unchanged to suppress liquid surface convection, make the melt temperature evenly distributed, and improve the quality of single crystal silicon.

[0006] Preferably, in step S1, the predetermined distance is NCP+140mm~+160mm.

[0007] Preferably, in step S2, the magnetic field strength is 0.4T.

[0008] Preferably, during the crystal pulling process, the position of the liquid-to-mouth distance is adjusted and maintained unchanged.

[0009] Preferably, the liquid port distance is 45-55 mm.

[0010] Preferably, during the crystal pulling process, cooling water is introduced into the water-cooling jacket and the furnace drum to control the growth rate of the single crystal silicon and improve the quality of the single crystal silicon.

[0011] The present invention also provides a single crystal ingot, which is pulled by using the method for preparing low-oxygen high-quality single crystal silicon as described above to obtain the ingot.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing low-oxygen, high-quality single crystal silicon of the present invention comprises the following steps: when pulling a 12-inch crystal rod, during the crystal pulling process, adjusting the heater to rise to a predetermined distance so that the heating zone of the heater is located above the liquid surface of the silicon melt to reduce the oxygen content of the single crystal silicon; during the rising process of the heater, applying a horizontal magnetic field, adjusting the center position of the magnetic field to be flush with the liquid surface position, and controlling the magnetic field strength to remain unchanged to suppress liquid surface convection, make the melt temperature evenly distributed, and improve the quality of the single crystal silicon, thereby reducing the oxygen content of the single crystal silicon while ensuring the quality of the single crystal silicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the structure of the device for preparing single crystal silicon according to the present invention.

[0014] Figure 2 This is a simulation diagram of oxygen content distribution in Example 1.

[0015] Figure 3 This is a simulated diagram of oxygen content distribution of comparative example 1.

[0016] Figure 4 The radial oxygen content variation curves of the crystal rods of Example 1 and Comparative Example 1 are shown.

[0017] Figure 5 The graphs are the lateral oxygen content variation curves of the crystal rods of Example 1 and Comparative Example 1.

[0018] Figure 6 The oxygen content variation curves of Example 1, Comparative Example 1 and Comparative Example 2 are shown.

[0019] In the figure: water cooling jacket 1, heat shield 2, thermal insulation material 3, magnetic field 4, furnace tube 5, heater 6, liquid port distance 7. DETAILED DESCRIPTION

[0020] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0021] A method for preparing low-oxygen high-quality single crystal silicon comprises the following steps: S1. During the crystal pulling process, the heater is adjusted to rise to a predetermined distance so that the heating area of ​​the heater is located above the liquid surface of the silicon melt to reduce the oxygen content of the single crystal silicon; S2. During the rising process of the heater, a horizontal magnetic field is applied, the center position of the magnetic field is adjusted to be level with the liquid surface, and the magnetic field strength is controlled to remain unchanged to suppress liquid surface convection, make the melt temperature evenly distributed, and improve the quality of single crystal silicon.

[0022] Please see Figure 1 The method for preparing low-oxygen and high-quality single crystal silicon of the present invention is as follows: when pulling a 12-inch crystal rod, during the crystal pulling process, the heater 6 is adjusted to rise to a predetermined distance so that the heating area of ​​the heater 6 is located above the liquid surface of the silicon melt to reduce the oxygen content of the single crystal silicon; during the rising process of the heater 6, a horizontal magnetic field 4 is applied, and the center position of the magnetic field 4 is adjusted to be flush with the liquid surface position, and the magnetic field strength is controlled to remain unchanged to suppress liquid surface convection, make the melt temperature uniform, and improve the quality of the single crystal silicon, thereby reducing the oxygen content of the single crystal silicon while ensuring the quality of the single crystal silicon.

[0023] Further, in step S1, the predetermined distance is NCP+140mm~+160mm. After the material is oxidized, the heater is adjusted to rise to move the heating zone of the heater upward so that the heating zone of the heater is located above the liquid surface of the silicon melt, and the reaction temperature of the quartz crucible is adjusted to reduce the oxygen content. In addition, the heating zone of the heater is located above the liquid surface of the silicon melt, which can accelerate the flow rate of argon gas on the surface of the silicon melt, thereby promoting the evaporation of SiO gas from the solution, thereby reducing the oxygen content of the single crystal silicon.

[0024] Further, in step S2, the magnetic field strength is 0.4 T. On the one hand, the magnetic field can suppress the convection movement in the melt, so that the heat is conducted more evenly, thereby reducing defects and impurities in the crystal. On the other hand, the magnetic field can also affect the transport behavior of the solute in the molten pool, making the composition of the crystal more uniform, reducing the segregation effect of the crystal, and thus improving the growth quality.

[0025] Furthermore, during the crystal pulling process, the position of the liquid mouth distance 7 is adjusted and the liquid mouth distance 7 is kept unchanged. After the heater rises, the hot zone changes, and the liquid mouth distance needs to be adjusted to a suitable position. On the one hand, the temperature inside the crystal furnace is stabilized to ensure that the temperature inside the crystal furnace is evenly distributed, so that the crystal melting temperature is evenly distributed, thereby ensuring that the arrangement of the single crystal silicon atoms is uniform and it is not easy to break, thereby improving the quality of the crystal after being taken out of the furnace. On the other hand, the liquid mouth distance is in a suitable position, so that the airflow's ability to blow above the melt surface is enhanced, which is conducive to the volatilization of SiO gas, thereby reducing the oxygen content of the single crystal silicon.

[0026] Furthermore, the liquid port distance 7 is 45-55 mm.

[0027] Furthermore, during the crystal pulling process, cooling water is introduced into the water-cooling jacket 1 and the furnace barrel 5 to control the growth rate of the single crystal silicon and improve the quality of the single crystal silicon. Among them, water cooling is an important link in the crystal pulling process. By introducing cooling water into the water-cooling jacket and the furnace barrel, the heat generated during the crystal pulling process is quickly taken away to ensure the uniformity and quality of crystal growth. Among them, the heat shield 2 is placed above the thermal field, and there must be no gaps or offsets. The heat insulation material 3 is set between the furnace barrel 5 and the heater 6 to maintain the melt temperature during the crystal pulling process through the heat shield 2 and the heat insulation material 3, so that the melt temperature is evenly distributed and the quality of the single crystal silicon is improved.

[0028] The present invention also provides a single crystal ingot, which is pulled by using the method for preparing low-oxygen high-quality single crystal silicon as described above to obtain the ingot. Embodiment 1:

[0029] In the single crystal furnace, the MCZ method is used to pull crystal rods to pull 12-inch single crystals. During the crystal pulling process, the heater is adjusted to rise NCP+150mm. During the rising process of the heater, a 0.4T horizontal magnetic field is applied, the center position of the magnetic field is adjusted to be level with the liquid level, and the magnetic field strength is controlled to remain unchanged; the liquid nozzle distance is adjusted to 50mm. During the crystal pulling process, the liquid nozzle distance remains unchanged, and the crystal rod is pulled to obtain a crystal rod.

[0030] Comparative Example 1: In the single crystal furnace, the MCZ method is used to pull the crystal rod to pull a 12-inch single crystal. During the crystal pulling process, the heater does not rise, and a 0.4T horizontal magnetic field is applied. The center position of the magnetic field is adjusted to be level with the liquid level, and the magnetic field strength is controlled to remain unchanged. The liquid mouth distance is adjusted to 50mm. During the crystal pulling process, the liquid mouth distance remains unchanged, and the crystal rod is pulled to obtain a crystal rod.

[0031] Comparative Example 2: In the single crystal furnace, the MCZ method is used to pull crystal rods to pull 12-inch single crystals. During the crystal pulling process, the heater is adjusted to rise NCP+100mm. During the rising process of the heater, a horizontal magnetic field is applied, and the center position of the magnetic field is adjusted to be below the liquid surface. The magnetic field strength is reduced in the equal diameter stage; the liquid mouth distance is adjusted to 30mm. During the crystal pulling process, the liquid mouth distance remains unchanged, and the crystal rod is pulled to obtain a crystal rod.

[0032] Oxygen content detection: Using the method of Example 1, the results of ANSYS simulation of the oxygen content distribution of the crystal rod are as follows: Figure 2 The results of testing the oxygen content distribution of the crystal rod in the radial and transverse directions are as follows: Figure 4 , Figure 5 ; By using the method of comparative example 1, the results of simulating the oxygen content distribution of the crystal rod by ANSYS are as follows Figure 3 The results of testing the oxygen content distribution of the crystal rod in the radial and transverse directions are as follows: Figure 4 , Figure 5 ; Comparative Example 1, Comparative Example 1, Comparative Example 2 oxygen content change curve as shown Figure 6 Through the above Figure 2-Figure 6 It can be seen that the oxygen content of the crystal rod obtained in Example 1 is lower than the oxygen content of the crystal rod obtained in Comparative Example 1 and Comparative Example 2.

[0033] The crystal rods obtained in Example 1 and Comparative Example 2 were subjected to defect detection by using a surface light scattering (LLS) scanning technique. The detection results are shown in Table 1.

[0034] Table 1

[0035] It can be seen from the above table that the quality of the crystal rod obtained in Example 1 is better than the quality of the crystal rod obtained in Comparative Example 2.

[0036] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for preparing low-oxygen high-quality single crystal silicon, characterized in that: The following steps are involved: S1. During the crystal pulling process, the heater is adjusted to rise to a predetermined distance so that the heating area of ​​the heater is located above the liquid surface of the silicon melt to reduce the oxygen content of the single crystal silicon; S2. During the rising process of the heater, a horizontal magnetic field is applied, the center position of the magnetic field is adjusted to be level with the liquid surface, and the magnetic field strength is controlled to remain unchanged to suppress liquid surface convection, make the melt temperature evenly distributed, and improve the quality of single crystal silicon.

2. The method for preparing low-oxygen high-quality single crystal silicon according to claim 1, characterized in that: In step S1, the predetermined distance is NCP+140mm~+160mm.

3. The method for preparing low-oxygen high-quality single crystal silicon according to claim 1, characterized in that: In step S2, the magnetic field strength is 0.4T.

4. The method for preparing low-oxygen high-quality single crystal silicon according to claim 1, characterized in that: During the crystal pulling process, the position of the liquid nozzle distance is adjusted and kept constant.

5. The method for preparing low-oxygen high-quality single crystal silicon according to claim 4, characterized in that: The liquid port distance is 45-55mm.

6. The method for preparing low-oxygen high-quality single crystal silicon according to any one of claims 1 to 5, characterized in that: During the crystal pulling process, cooling water is introduced into the water-cooling jacket and the furnace barrel to control the growth rate of single crystal silicon and improve the quality of single crystal silicon.

7. A single crystal ingot, characterized in that: The low-oxygen high-quality single crystal silicon preparation method according to any one of claims 1 to 6 is used for pulling to obtain a crystal rod.

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