Czochralski method for reducing the defect density of a heavy arsenic-doped <111> single crystal silicon section and a single crystal silicon rod

Abstract

The application provides a method for reducing the cross-section defect density of a heavy arsenic-doped <111> single crystal silicon rod and a single crystal silicon rod, and belongs to the technical field of single crystal silicon pulling. First, a single crystal is pulled using a predetermined thermal field of a single crystal furnace to increase the height of a thermal zone in the pulling process. In the constant diameter process, the liquid port distance is constant, the pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, and the ratio (CR / SR) of the crystal rotation to the pot rotation is adjusted, so that the growth rate of the crystal, the temperature gradient of the solid-liquid interface and the deposition of the oxide are controlled to make the heat conduction uniformly transmit along the radial direction of the crystal rod, and the point defects such as interstitial atoms and vacancies have more opportunities to diffuse outward during the crystal growth process, thereby inhibiting the generation of point defects and impurity decoration, reducing the cross-section defect density of the single crystal silicon rod and improving the quality of the heavy arsenic-doped crystal rod.

Description

Technical Field

[0001] This invention relates to the field of single-crystal silicon crystal pulling technology, and particularly to a method for reducing heavy arsenic doping. <111> Crystal pulling method for crystal orientation single-crystal silicon cross-sectional defect density and single-crystal silicon rod. Background Technology

[0002] During crystal growth, thermodynamic fluctuations can induce the formation of arsenic clusters, precipitates, and lattice defects adorned with impurities in the microstructure of the crystal rod cross-section, especially in heavily arsenic-doped crystals. <111> During the Czochralski single crystal growth process, the thermal convection of the silicon solution causes small periodic fluctuations in temperature and arsenic segregation at the solid-liquid interface, resulting in a periodic oscillating distribution of arsenic concentration in the crystal.

[0003] Specifically, in heavily arsenic-doped <111> During the Czochralski growth of crystal-oriented single-crystal silicon, because the covalent radius of arsenic atoms is larger than that of silicon atoms, when a large number of arsenic atoms replace silicon lattice positions, significant lattice mismatch stress is introduced, leading to an increase in the local lattice constant of silicon (lattice expansion). To release this stress, a large number of extended defects such as dislocations are formed inside the crystal, increasing the defect density. Arsenic atoms tend to cluster around these defects, forming the so-called "impurity decoration" phenomenon. In microscopic observation, arsenic-rich regions distributed along dislocation lines or defect clusters displayed in the form of etch pits can be observed. Their distribution reflects the density and morphology of dislocations and other defects in the crystal. From substrate preparation to epitaxial processes, the above-mentioned defects and arsenic precipitates become carrier recombination centers and sources of disturbance in epitaxial growth, leading to a decrease in the quality of the epitaxial layer. This manifests as a significantly higher forward voltage drop (VF) in the device, severely reducing the yield of the final product. Summary of the Invention

[0004] In view of this, and to address the above shortcomings, it is necessary to propose a method to reduce heavy arsenic doping. <111> A crystal pulling method for reducing the cross-sectional defect density of single-crystal silicon with different crystal orientations, in order to improve the quality of heavily arsenic-doped crystal rods; It is also necessary to provide a single-crystal silicon rod.

[0005] The technical solution adopted by this invention to solve its technical problem is: On the one hand, the present invention provides a method for reducing heavy arsenic doping. <111> A crystal pulling method for determining the cross-sectional defect density of single-crystal silicon with specific crystal orientation includes the following steps: S1: Use the predetermined hot zone of the single crystal furnace to pull single crystals in order to increase the height of the hot zone during the crystal pulling process; S2: During the constant diameter process, the liquid outlet distance remains constant. The pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, and the crystal rotation / boiler rotation ratio (CR / SR) is adjusted so that the heat conduction is uniformly transmitted along the radial direction of the crystal rod, suppressing the formation of point defects and impurity decorations.

[0006] Preferably, in S1, “using the predetermined hot zone of the single crystal furnace to pull crystals” specifically means: keeping the total height of the middle insulation cylinder and the upper insulation cylinder unchanged in the predetermined hot zone, increasing the height of the middle insulation cylinder to the predetermined height, adjusting the height of the upper insulation cylinder at the same time, increasing the installation height of the heater support, and reducing the vertical heating height of the heater heating ring.

[0007] Preferably, the total height of the middle insulation cylinder and the upper insulation cylinder is 630mm-650mm, the predetermined height of the middle insulation cylinder is 555mm-565mm, the height of the upper insulation cylinder is 75mm-85mm, the installation height of the heater support is 315mm-325mm, and the vertical heating height of the heater heating ring is 295mm-305mm.

[0008] Preferably, S2 is as follows: S21: When pulling from the constant diameter to the first predetermined length, the liquid nozzle distance remains constant, and the crystal rod is pulled using a constant first target pulling speed and a constant first target CR / SR. S22: When pulling from the first predetermined length to the second predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant second target pulling speed and a constant second target CR / SR. S23: When pulling from the second predetermined length to the third predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant third target pulling speed and a constant third target CR / SR. S24: From the third predetermined length to the end of the constant diameter, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant fourth target pulling speed and a constant fourth target CR / SR. The first target pulling speed, the second target pulling speed, the third target pulling speed, and the fourth target pulling speed decrease sequentially.

[0009] Preferably, the liquid outlet distance is 40mm-45mm.

[0010] Preferably, in step S21, the first predetermined length is 100mm-110mm, the first target pulling speed is 1mm / min, and the upper and lower limits of the first target pulling speed are 1.5mm / min-0.3mm / min, and the first target CR / SR is 8rpm / 18rpm.

[0011] Preferably, in step S22, the second predetermined length is 200mm-210mm, the second target pulling speed is 0.9mm / min, and the upper and lower limits of the second target pulling speed are 1.2mm / min-0.5mm / min, and the first target CR / SR is 7rpm / 17rpm.

[0012] Preferably, in step S23, the third predetermined length is 300mm-310mm, the third target pulling speed is 0.75mm / min, and the upper and lower limits of the third target pulling speed are 0.9mm / min-0.55mm / min, and the first target CR / SR is 6rpm / 16rpm.

[0013] Preferably, in S24, the fourth target pulling speed is 0.68 mm / min, and the upper and lower limits of the fourth target pulling speed are 0.78 mm / min-0.58 mm / min, and the first target CR / SR is 6 rpm / 15 rpm.

[0014] On the other hand, the present invention provides a single-crystal silicon rod that reduces heavy arsenic doping as described in the preceding aspect. <111> It is produced by a crystal pulling method that measures the cross-sectional defect density of single-crystal silicon.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for reducing heavy arsenic doping. <111> The crystal pulling method for reducing the cross-sectional defect density of single-crystal silicon first uses a predetermined thermal field in a single-crystal furnace to pull the single crystal, thereby increasing the height of the hot zone during the crystal pulling process. During the constant diameter process, the liquid outlet distance remains constant. The pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, and the crystal rotation / boiler rotation ratio (CR / SR) is adjusted. In this way, by controlling the crystal growth rate, the temperature gradient at the solid-liquid interface, and the precipitation of oxides, heat conduction is uniformly transmitted along the radial direction of the crystal rod. During the crystal growth process, point defects such as interstitial atoms and vacancies have more opportunities to diffuse outward, thereby suppressing the generation of point defects and impurity decorations, reducing the cross-sectional defect density of the single-crystal silicon rod, and improving the quality of the heavily arsenic-doped crystal rod. Attached Figure Description

[0016] Figure 1 The present invention provides a method for reducing heavy arsenic doping. <111> A flowchart of a crystal pulling method for determining the cross-sectional defect density of single-crystal silicon with specific crystal orientation.

[0017] Figure 2 This is a structural diagram of the predetermined thermal field of the single crystal furnace in an embodiment of the method of the present invention.

[0018] Figure 3 This is a diagram showing the cross-sectional defect detection results of the crystal rod obtained in an embodiment of the method of the present invention.

[0019] Figure 4 This is a structural diagram of the predetermined thermal field of a single crystal furnace in a comparative example using traditional methods.

[0020] Figure 5 The image shows the cross-sectional defect detection results of the crystal rod obtained by the traditional method.

[0021] In the diagram: middle insulation cylinder 10, upper insulation cylinder 20, heater support 30, heater heating ring 40. Detailed Implementation

[0022] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0023] Please refer to Figure 1 This invention provides a method for reducing heavy arsenic doping. <111> A crystal pulling method for determining the cross-sectional defect density of single-crystal silicon with specific crystal orientation includes the following steps: S1: Use the predetermined hot zone of the single crystal furnace to pull single crystals in order to increase the height of the hot zone during the crystal pulling process; S2: During the constant diameter process, the liquid outlet distance remains constant. The pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, and the crystal rotation / boiler rotation ratio (CR / SR) is adjusted so that the heat conduction is uniformly transmitted along the radial direction of the crystal rod, suppressing the formation of point defects and impurity decorations.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: First, a single crystal is pulled using a predetermined hot zone in a single crystal furnace to increase the height of the hot zone during the crystal pulling process. Then, during the constant diameter process, the liquid outlet distance remains constant, and the pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, while the crystal rotation / boiler rotation ratio (CR / SR) is adjusted. In this way, by controlling the crystal growth rate, the temperature gradient at the solid-liquid interface, and the precipitation of oxides, heat conduction is made uniformly transmitted along the radial direction of the crystal rod. During the crystal growth process, point defects such as interstitial atoms and vacancies have more opportunities to diffuse outward, thereby suppressing the generation of point defects and impurity decorations, reducing the cross-sectional defect density of the single crystal silicon rod, and improving the quality of the heavily arsenic-doped crystal rod.

[0025] Specifically, by using a predetermined thermal field in a single-crystal furnace to pull single crystals, the height of the hot zone during the crystal pulling process is increased, thereby reducing the lateral temperature gradient in the crystal near the crystallization interface. This also enhances the in-situ heat treatment effect, providing sufficient diffusion and recombination conditions for point defects such as interstitial atoms and vacancies in the crystal. Under this thermal field condition, a gradually decreasing crystal pulling speed helps form a flat or slightly convex melt at the solid-liquid interface, reducing thermal disturbance during growth and weakening forced convection of the melt. This reduces the scouring intensity of the melt on the quartz crucible wall, suppressing the crucible corrosion rate and oxygen solubility. Simultaneously, by adjusting the crystal rotation / crate rotation ratio (CR / SR) in segments with the pulling speed, a stable and symmetrical melt flow field is established, avoiding severe or unstable turbulence and smoothly controlling the oxygen transport process to promote oxygen volatilization at the solid-liquid interface. Furthermore, by maintaining a constant liquid outlet distance throughout the crystal pulling process, the stability and consistency of the crystal growth environment are further ensured, thus suppressing the formation of point defects and impurity decorations and improving the quality of heavily doped arsenic rods.

[0026] Furthermore, in S1, “using the predetermined hot zone of the single crystal furnace to pull crystals” specifically means: in the predetermined hot zone, while keeping the total height of the middle insulation cylinder 10 and the upper insulation cylinder 20 unchanged, the middle insulation cylinder 10 is increased to the predetermined height, while the height of the upper insulation cylinder 20 is adjusted, and the installation height of the heater support 30 is increased, while the vertical heating height of the heater heating ring 40 is reduced.

[0027] Specifically, in this invention, the single crystal furnace adopts the 1806 furnace type. In step S1, the total height of the middle insulation cylinder 10 and the upper insulation cylinder 20 is 630mm-650mm, the predetermined height of the middle insulation cylinder 10 is 555-565mm, the height of the upper insulation cylinder 20 is 75mm-85mm, the installation height of the heater support 30 is 315mm-325mm, and the vertical heating height of the heater heating ring 40 is 295mm-305mm. Preferably, the total height of the middle insulation cylinder 10 and the upper insulation cylinder 20 is 640mm, the predetermined height of the middle insulation cylinder 10 is 560mm, the installation height of the heater support 30 is 320mm, and the vertical heating height of the heater heating ring 40 is 300mm.

[0028] Furthermore, S2 specifically refers to: S21: When pulling the crystal rod from the constant diameter to the first predetermined length, the liquid nozzle distance remains constant, and the crystal rod is pulled using a constant first target pulling speed and a constant first target CR / SR to ensure that the crystal growth interface forms a moderate undercooling to maintain the single crystal growth power. S22: When pulling from the first predetermined length to the second predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant second target pulling speed and a constant second target CR / SR to ensure the stability of melt convection, promote the effective volatilization of oxygen content and reduce its transport to the crystal center, while maintaining a flat or slightly convex solid-liquid interface morphology. S23: When pulling from the second predetermined length to the third predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant third target pulling speed and a constant third target CR / SR to ensure that the segregation of arsenic impurities at the solid-liquid interface tends to be stable, reducing concentration fluctuations, thereby inhibiting the formation of arsenic clusters and precipitates. S24: From the third predetermined length to the end of the equal diameter, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant fourth target pulling speed and a constant fourth target CR / SR to ensure that the crystal stays in the high temperature zone of the single crystal furnace for a sufficient time, so that vacancies and interstitial atoms have enough time to diffuse and recombine, effectively reducing the overall defect density of the crystal. The first, second, third, and fourth target pulling speeds decrease sequentially. A higher first target pulling speed helps to quickly pass through the high-temperature region where a large number of point defects are generated. The pulling speed is gradually reduced in the later stages to prolong the residence time of the crystal in the high-temperature region, providing a more sufficient time window for the mutual diffusion and recombination of vacancies and interstitial atoms. At the same time, different pulling speeds are adapted to different CR / SR ratios to avoid violent and unstable turbulence, thereby smoothly controlling oxygen transport. Specifically, crystal rotation (CR) helps oxygen volatilize near the crystal growth interface, while pot rotation (SR) determines the intensity of oxygen transport from the crucible wall to the center of the melt. The oxygen "vaporization-transport" balance is dynamically regulated by adjusting the CR / SR ratio.

[0029] Furthermore, the liquid nozzle distance is 44mm-45mm, preferably 45mm. Compared to a smaller liquid nozzle distance, the liquid nozzle distance in this invention slows down the cooling rate of the crystal. It works synergistically with the "segmented reduction of pulling speed" to extend the residence time of the crystal in the high-temperature region, providing a sufficient time window for the mutual diffusion and recombination of vacancies and interstitial atoms.

[0030] Furthermore, in S21, the first predetermined length is 100mm-110mm, the first target pulling speed is 1mm / min, and the upper and lower limits of the first target pulling speed are 1.5mm / min-0.3mm / min, and the first target CR / SR is 8rpm / 18rpm.

[0031] Furthermore, in S22, the second predetermined length is 200mm-210mm, the second target pulling speed is 0.9mm / min, and the upper and lower limits of the second target pulling speed are 1.2mm / min-0.5mm / min, and the first target CR / SR is 7rpm / 17rpm.

[0032] Furthermore, in S23, the third predetermined length is 300mm-310mm, the third target pulling speed is 0.75mm / min, and the upper and lower limits of the third target pulling speed are 0.9mm / min-0.55mm / min, and the first target CR / SR is 6rpm / 16rpm.

[0033] Furthermore, in S24, the fourth target pulling speed is 0.68 mm / min, and the upper and lower limits of the fourth target pulling speed are 0.78 mm / min-0.58 mm / min, and the first target CR / SR is 6 rpm / 15 rpm.

[0034] On the other hand, the present invention provides a single-crystal silicon rod that reduces heavy arsenic doping as described in the preceding aspect. <111> It is produced by a crystal pulling method that measures the cross-sectional defect density of single-crystal silicon.

[0035] To further understand the present invention, the following examples of heavily arsenic-doped methods and comparative examples of conventional methods illustrate the present invention. <111> The pulling process of crystal-oriented monocrystalline silicon and the detection results of cross-sectional defects.

[0036] Example: Using an 1806 single crystal furnace, pull 5-inch heavily arsenic-doped crystals. <111> For crystal orientation single-crystal silicon rods, please refer to [link / reference]. Figure 2 The total height of the middle insulation cylinder 10 and the upper insulation cylinder 20 of the 1806 single crystal furnace is 640 mm. The predetermined height of the middle insulation cylinder 10 is 560 mm, the height of the upper insulation cylinder 20 is 80 mm, the installation height of the heater support 30 is 320 mm, and the vertical heating height of the heater heating ring 40 is 300 mm. During the crystal rod pulling process, the liquid outlet distance is constant at 45 mm. The target pulling speed setting and the upper and lower limits of the pulling speed during the constant diameter process are shown in Table 1. The crystal rotation / pot rotation ratio (CR / SR) is shown in Table 2. After obtaining the crystal rod, the crystal rod is rolled, cut, and sliced ​​to obtain six silicon wafers of equal diameters of 0mm, 300mm, 600mm, 900mm, 1100mm, and 1400mm. The six silicon wafers are placed in a high-temperature heat treatment at 1100℃ for 2 hours and then subjected to preferential etching in Sirtl liquid for 3 minutes. The cross-sectional defect detection results are observed using an electron microscope, as shown in Figure 3.

[0037] Table 1

[0038] Table 2

[0039] Comparative example: Using an 1806 single crystal furnace, 5-inch heavily arsenic-doped crystals were pulled. <111> For crystal orientation single-crystal silicon rods, please refer to [link / reference]. Figure 4 The total height of the middle insulation cylinder 10 and the upper insulation cylinder 20 of the 1806 single crystal furnace is 640 mm. The predetermined height of the middle insulation cylinder 10 is 500 mm, the height of the upper insulation cylinder 20 is 140 mm, the installation height of the heater support 30 is 120 mm, and the vertical heating height of the heater heating ring 40 is 400 mm. During the crystal pulling process, the liquid outlet distance is constant at 30 mm. The target pulling speed settings during the constant diameter process are shown in Table 3. The ratio of CR / SR is shown in Table 4. After obtaining the crystal rod, the crystal rod is rolled, cut, and sliced ​​to obtain six silicon wafers of equal diameters of 0mm, 300mm, 600mm, 900mm, 1100mm, and 1400mm. The six silicon wafers are placed in a high-temperature heat treatment at 1100℃ for 2 hours and then subjected to preferential etching with Sirtl liquid for 3 minutes. The cross-sectional defect detection results are observed with an electron microscope, as shown in Figure 5.

[0040] Table 3

[0041] Table 4

[0042] Please refer to Figure 5 It can be clearly observed that the cross-section of the crystal rod obtained in the comparative example contains micro-defects and impurities, with a relatively high defect density. Please refer to [link / reference needed]. Figure 3 It can be observed that the cross-section of the crystal rod obtained by the method embodiment of the present invention is free of impurity contamination and the defect density is 0. The above comparison proves that the present application effectively improves the performance of heavily arsenic-doped crystals. <111> The quality of crystal-oriented single-crystal silicon rods improves the yield rate of devices.

[0043] 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 method for reducing heavy arsenic doping <111> A crystal pulling method for determining the cross-sectional defect density of single-crystal silicon with specific crystal orientation, characterized in that... Includes the following steps: S1: Use the predetermined hot zone of the single crystal furnace to pull single crystals in order to increase the height of the hot zone during the crystal pulling process; S2: During the constant diameter process, the liquid outlet distance remains constant. The pulling speed of the crystal rod is gradually reduced according to the length of the crystal rod, and the crystal rotation / boiler rotation ratio (CR / SR) is adjusted so that the heat conduction is uniformly transmitted along the radial direction of the crystal rod, suppressing the generation of point defects and impurity decorations. The "crystal pulling using a predetermined hot zone of a single crystal furnace" in S1 specifically refers to: keeping the total height of the middle and upper insulation cylinders constant within the predetermined hot zone, increasing the height of the middle insulation cylinder to a predetermined height, adjusting the height of the upper insulation cylinder, increasing the installation height of the heater support, and decreasing the vertical heating height of the heater heating ring; the total height of the middle and upper insulation cylinders is 630mm-650mm, the predetermined height of the middle insulation cylinder is 555mm-565mm, the height of the upper insulation cylinder is 75mm-85mm, the installation height of the heater support is 315mm-325mm, and the vertical heating height of the heater heating ring is 295mm-305mm; S2 specifically refers to: S21: When pulling from the constant diameter to the first predetermined length, the liquid nozzle distance remains constant, and the crystal rod is pulled using a constant first target pulling speed and a constant first target CR / SR. S22: When pulling from the first predetermined length to the second predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant second target pulling speed and a constant second target CR / SR. S23: When pulling from the second predetermined length to the third predetermined length, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant third target pulling speed and a constant third target CR / SR. S24: From the third predetermined length to the end of the constant diameter, the liquid outlet distance remains constant, and the crystal rod is pulled using a constant fourth target pulling speed and a constant fourth target CR / SR. The pulling speeds of the first target, the second target, the third target, and the fourth target decrease sequentially. In S21, the first predetermined length is 100mm-110mm, the first target pulling speed is 1mm / min, and the upper and lower limits of the first target pulling speed are 1.5mm / min-0.3mm / min, and the first target CR / SR is 8rpm / 18rpm. In S22, the second predetermined length is 200mm-210mm, the second target pulling speed is 0.9mm / min, and the upper and lower limits of the second target pulling speed are 1.2mm / min-0.5mm / min, and the first target CR / SR is 7rpm / 17rpm; In S23, the third predetermined length is 300mm-310mm, the third target pulling speed is 0.75mm / min, and the upper and lower limits of the third target pulling speed are 0.9mm / min-0.55mm / min, and the first target CR / SR is 6rpm / 16rpm; In S24, the fourth target pulling speed is 0.68 mm / min, and the upper and lower limits of the fourth target pulling speed are 0.78 mm / min-0.58 mm / min, and the first target CR / SR is 6 rpm / 15 rpm.

2. The method for reducing heavy arsenic doping as described in claim 1 <111> A crystal pulling method for determining the cross-sectional defect density of single-crystal silicon with specific crystal orientation, characterized in that... The distance between the liquid outlets is 40mm-45mm.

3. A single-crystal silicon rod, characterized in that, By reducing heavy arsenic doping as described in any one of claims 1-2 <111> It is produced by a crystal pulling method that measures the cross-sectional defect density of single-crystal silicon.

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