Thermal Field and Crystal Pulling Method for Improving Electrical Uniformity of Terminal Products

Abstract

The present invention provides a thermal field and crystal pulling method for improving the electrical property uniformity of terminal products, which relates to the technical field of heavily doped single crystal silicon crystal pulling. By providing a hollow layer below the lower part of the upper heat insulation material for temperature reduction, the temperature reduction heat shield is located above the quartz crucible, the upper heat insulation material for temperature reduction is located above the heat insulation material part, the upper end of the temperature reduction heat shield overlaps with the upper part of the upper heat insulation material for temperature reduction, and the upper heat insulation material for temperature reduction is assembled with the heat insulation material part to improve the temperature gradient of the thermal field, so as to increase the temperature gradient. Furthermore, during the crystal pulling process, the residence time of the crystal rod at 800°C - 1100°C is shortened, the defect growth cycle is shortened, and microdefects formed by the coalescence of homogeneous nucleation and heterogeneous nucleation through supersaturated precipitation are avoided, thereby reducing the microdefect density and improving the performance uniformity of the terminal product.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulling heavily doped single crystal silicon, and particularly relates to a thermal field and a crystal pulling method for improving the electrical uniformity of end products. Background Art

[0002] Defects in heavily doped products will seriously affect the performance uniformity of end products. For example, in the case of heavily doped red phosphorus, arsenic, antimony, etc., microdefects will be generated during the crystal pulling process. These microdefects will lead to a decrease in local carrier mobility or an increase in leakage current, as well as uneven electric field distribution in the crystal, resulting in local electric field concentration or electric field shielding effect, making the performance non-uniform. Therefore, in order to improve the performance uniformity of end products, a new crystal pulling method needs to be developed to eliminate the microdefects existing in the crystal rod and improve the product quality. Summary of the Invention

[0003] In view of this, the present invention provides a thermal field and a crystal pulling method for improving the electrical uniformity of end products.

[0004] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0005] A thermal field for improving the electrical uniformity of end products includes a quartz crucible, a heating component, a heat insulation part. The heating component is located at the bottom and side of the quartz crucible. The heating component arranged on the side of the quartz crucible is located between the quartz crucible and the heat insulation part. The heat insulation part is located in the circumferential direction of the quartz crucible. It further includes a cooling component. The cooling component includes a cooling heat shield part and an upper cooling heat insulation material. A hollow layer is arranged at the lower part of the upper cooling heat insulation material. The cooling heat shield part is located above the quartz crucible. The upper cooling heat insulation material is located above the heat insulation part. The upper end of the cooling heat shield part overlaps with the upper part of the upper cooling heat insulation material. The upper cooling heat insulation material is assembled with the heat insulation part to shorten the residence time of the crystal rod at 800°C - 1100°C and reduce the microdefect density.

[0006] Preferably, the height of the hollow layer is 1 / 4 - 1 / 2 of the height of the upper cooling heat insulation material.

[0007] Preferably, the thickness of the upper cooling heat insulation material is 15 - 20 mm.

[0008] Preferably, the cooling component further includes a graphite part, and the graphite part is assembled with the heat insulation part and the upper cooling heat insulation material.

[0009] Preferably, the temperature-reducing thermal screen part includes: a thermal screen, a lifting ring, and a support ring. The lifting ring is located on the support ring, the support ring is located on the upper heat-insulating material of the temperature reduction part, the upper part of the thermal screen is connected to the thermal screen lifting ring, the thermal screen lifting ring overlaps on the support ring, and the support ring is embedded in the upper heat-insulating material of the temperature reduction part.

[0010] Preferably, the thermal screen includes an inner thermal screen, an outer thermal screen, and a thermal screen heat-insulating material. The inner thermal screen is sleeved inside the outer thermal screen, and the thermal screen heat-insulating material is filled between the inner thermal screen and the outer thermal screen.

[0011] Preferably, both the inner thermal screen and the outer thermal screen are provided with straight-section parts and curved-section parts, and the linear distance between the straight-section part of the inner thermal screen and the straight-section part of the outer thermal screen is reduced by 1 / 3 - 1 / 2.

[0012] Preferably, the heat-insulating material part includes a middle heat-insulating material and a lower heat-insulating material. The upper heat-insulating material of the temperature reduction part, the middle heat-insulating material, and the lower heat-insulating material are arranged in sequence from top to bottom. The bottom of the upper heat-insulating material is assembled with one end of the middle heat-insulating material, and the other end of the middle heat-insulating material is assembled with the lower heat-insulating material.

[0013] Preferably, the heating assembly includes a bottom heater and a side heater. The bottom heater is located at the bottom of the quartz crucible, and the side heater is located between the quartz crucible and the heat-insulating material part to heat the quartz crucible.

[0014] The method of crystal pulling using the thermal field for improving the electrical property uniformity of the terminal product as described above includes an equal-diameter step. In the equal-diameter step: the argon flow rate is 50 - 90 slm, the furnace pressure is 8 - 12 kPa, the crucible rotation speed is 10 - 15 rpm, the crystal rotation speed is 12 - 20 rpm, and the pulling speed is 1.2 - 0.4 mm / min.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] A thermal field for improving the electrical property uniformity of the terminal product provided by the present invention, by arranging a hollow layer below the upper heat-insulating material of the temperature reduction part, the temperature-reducing thermal screen part is located above the quartz crucible, the upper heat-insulating material of the temperature reduction part is located above the heat-insulating material part, the upper end of the temperature-reducing thermal screen part overlaps above the upper heat-insulating material of the temperature reduction part, and the upper heat-insulating material of the temperature reduction part is assembled with the heat-insulating material part to improve the temperature gradient of the thermal field, so that the temperature gradient increases. Furthermore, during the crystal pulling process, the residence time of the crystal bar at 800°C - 1100°C is shortened, the defect growth cycle is shortened, and the microdefects formed by the coalescence of the already homogeneous nucleation and heterogeneous nucleation through supersaturated precipitation are avoided, thereby reducing the microdefect density and improving the performance uniformity of the terminal product. Description of the Drawings

[0017] Figure 1 Schematic diagram of the thermal field structure for improving the electrical uniformity of the terminal product.

[0018] Figure 2 Schematic diagram of the thermal field structure for Comparative Example 1.

[0019] Figure 3 Schematic diagram of the thermal field structure for Comparative Example 2.

[0020] Figure 4 Simulated thermal field gradient diagrams for Example 1, Comparative Example 1, and Comparative Example 2.

[0021] Figure 5 Thermal field temperature uniformity diagrams for Example 1, Comparative Example 1, and Comparative Example 2.

[0022] Figure 6 Macrograph of the silicon wafer to be detected with a diameter of 0 mm in Example 1.

[0023] Figure 7 Micrograph of the silicon wafer to be detected with a diameter of 0 mm in Example 1.

[0024] Figure 8 Macrograph of the silicon wafer to be detected with a diameter of 300 mm in Example 1.

[0025] Figure 9 Micrograph of the silicon wafer to be detected with a diameter of 300 mm in Example 1.

[0026] Figure 10 Macrograph of the silicon wafer to be detected with a diameter of 600 mm in Example 1.

[0027] Figure 11 Micrograph of the silicon wafer to be detected with a diameter of 600 mm in Example 1.

[0028] Figure 12 Macrograph of the silicon wafer to be detected with a diameter of 900 mm in Example 1.

[0029] Figure 13 Micrograph of the silicon wafer to be detected with a diameter of 900 mm in Example 1.

[0030] Figure 14 Macrograph of the silicon wafer to be detected with a diameter of 1200 mm in Example 1.

[0031] Figure 15 Micrograph of the silicon wafer to be detected with a diameter of 1200 mm in Example 1.

[0032] Figure 16 Macrograph of the silicon wafer to be detected with a diameter of 0 mm in Comparative Example 1.

[0033] FigureIt is the microscopic state diagram of the silicon wafer with an equal diameter of 0 mm to be detected in Comparative Example 1.

[0034] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 300 mm to be detected in Comparative Example 1.

[0035] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 300 mm to be detected in Comparative Example 1.

[0036] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 600 mm to be detected in Comparative Example 1.

[0037] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 600 mm to be detected in Comparative Example 1.

[0038] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 900 mm to be detected in Comparative Example 1.

[0039] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 900 mm to be detected in Comparative Example 1.

[0040] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 1200 mm to be detected in Comparative Example 1.

[0041] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 1200 mm to be detected in Comparative Example 1.

[0042] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 0 mm to be detected in Comparative Example 2.

[0043] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 0 mm to be detected in Comparative Example 2.

[0044] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 300 mm to be detected in Comparative Example 2.

[0045] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 300 mm to be detected in Comparative Example 2.

[0046] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 600 mm to be detected in Comparative Example 2.

[0047] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 600 mm to be detected in Comparative Example 2.

[0048] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 900 mm to be detected in Comparative Example 2.

[0049] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 900 mm to be detected in Comparative Example 2.

[0050] ​ It is the macroscopic state diagram of the silicon wafer with an equal diameter of 1200 mm to be detected in Comparative Example 2.

[0051] ​ It is the microscopic state diagram of the silicon wafer with an equal diameter of 1200 mm to be detected in Comparative Example 2.

[0052] In the figure: the thermal field 10 for improving the electrical uniformity of the end product, the quartz crucible 100, the heating assembly 200, the bottom heater 210, the side heater 220, the heat insulation part 300, the middle heat insulation material 310, the lower heat insulation material 320, the temperature reduction assembly 400, the temperature reduction heat shield part 410, the heat shield 411, the inner heat shield 4111, the outer heat shield 4112, the heat shield heat insulation material 4113, the straight section part 4114, the curved section part 4115, the lifting ring 412, the support ring 413, the upper temperature reduction heat insulation material 420, the hollow layer 421, the graphite part 430.

[0053] The thermal field 20 of Comparative Example 1, the upper heat insulation material 420a, the lower heat insulation material 320a, the heat shield 411a.

[0054] The thermal field 30 of Comparative Example 2, the upper heat insulation material 420b, the lower heat insulation material 320b, the heat shield 411b.

[0055] Plan1 refers to the simulation result of Comparative Document 2, Plan2 refers to the simulation result of Comparative Example 1, and Plan3 refers to the simulation result of Example 1. Specific Embodiments

[0056] The technical solutions and technical effects of the embodiments of the present invention will be further elaborated in detail below in conjunction with the drawings of the present invention.

[0057] Please refer to ​, A thermal field 10 for improving the electrical property uniformity of a terminal product, comprising a quartz crucible 100, a heating assembly 200, a heat insulation part 300. The heating assembly 200 is located at the bottom and side of the quartz crucible 100. The heating assembly 200 arranged on the side of the quartz crucible 100 is located between the quartz crucible 100 and the heat insulation part 300. The heat insulation part 300 is located in the circumferential direction of the quartz crucible 100. It further comprises a cooling assembly 400. The cooling assembly 400 comprises a cooling heat shield part 410 and an upper cooling heat insulation material 420. A hollow layer 421 is arranged at the lower part of the upper cooling heat insulation material 420. The cooling heat shield part 410 is located above the quartz crucible 100. The upper cooling heat insulation material 420 is located above the heat insulation part 300. The upper end of the cooling heat shield part 410 is lapped with the upper part of the upper cooling heat insulation material 420. The upper cooling heat insulation material 420 is assembled with the heat insulation part 300 to shorten the residence time of the crystal bar at 800°C - 1100°C, so as to reduce the microdefect density.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0059] The thermal field 10 for improving the electrical property uniformity of a terminal product provided by the present invention, by arranging a hollow layer 421 at the lower part of the upper cooling heat insulation material 420, the cooling heat shield part 410 is located above the quartz crucible 100, the upper cooling heat insulation material 420 is located above the heat insulation part 300, the upper end of the cooling heat shield part 410 is lapped with the upper part of the upper cooling heat insulation material 420, and the upper cooling heat insulation material 420 is assembled with the heat insulation part 300 to improve the temperature gradient of the thermal field, so that the temperature gradient increases. Furthermore, during the crystal pulling process, the residence time of the crystal bar at 800°C - 1100°C is shortened, the defect growth cycle is shortened, and microdefects formed by the coalescence of homogeneous nucleation and heterogeneous nucleation through supersaturated precipitation are avoided, thereby reducing the microdefect density and improving the performance uniformity of the terminal product.

[0060] Furthermore, the height of the hollow layer 421 is 1 / 4 - 1 / 2 of the height of the upper cooling heat insulation material 420.

[0061] Specifically, the hollow layer 421 can be openings at the bottom of the upper cooling heat insulation material 420.

[0062] Furthermore, the thickness of the upper cooling heat insulation material 420 is 15 - 20 mm, to avoid the deterioration of the temperature gradient and affect the quality defects of the crystal bar.

[0063] Furthermore, the cooling assembly 400 further comprises a graphite part 430. The graphite part 430 is assembled with the heat insulation part 300 and the upper cooling heat insulation material 420 to provide support for the upper cooling heat insulation material 420 and the heat insulation part 300.

[0064] Further, the cooling thermal shield part 410 includes: a thermal shield 411, a lifting ring 412, and a support ring 413. The lifting ring 412 is located on the support ring 413, the support ring 413 is located on the upper cooling heat insulation material 420, the upper part of the thermal shield 411 is connected to the thermal shield lifting ring 412, the thermal shield lifting ring 412 is lapped on the support ring 413, and the support ring 413 is embedded in the upper cooling heat insulation material 420.

[0065] Further, the thermal shield 411 includes an inner thermal shield 4111, an outer thermal shield 4112, and a thermal shield heat insulation material 4113. The inner thermal shield 4111 is sleeved inside the outer thermal shield 4112, and the thermal shield heat insulation material 4113 is filled between the inner thermal shield 4111 and the outer thermal shield 4112.

[0066] Further, both the inner thermal shield 4111 and the outer thermal shield 4112 are provided with straight section parts 4114 and curved section parts 4115. The linear distance between the straight section parts 4114 of the inner thermal shield 4111 and the straight section parts 4114 of the outer thermal shield 4112 is reduced by 1 / 3 - 1 / 2 to avoid the deterioration of the temperature gradient and affect the quality defects of the crystal bar.

[0067] Further, the heat insulation material part 300 includes a middle heat insulation material 310 and a lower heat insulation material 320. The upper cooling heat insulation material 420, the middle heat insulation material 310, and the lower heat insulation material 320 are arranged in sequence from top to bottom. The bottom of the upper heat insulation material is assembled with one end of the middle heat insulation material 310, and the other end of the middle heat insulation material 310 is assembled with the lower heat insulation material 320.

[0068] Further, the heating assembly 200 includes a bottom heater 210 and a side heater 220. The bottom heater 210 is located at the bottom of the quartz crucible 100, and the side heater 220 is located between the quartz crucible 100 and the heat insulation material part 300 to heat the quartz crucible 100.

[0069] The method of crystal pulling using the thermal field 10 for improving the electrical property uniformity of the end product as described above includes an equal - diameter step. In the equal - diameter step: the argon flow rate is 50 - 90 slm, the furnace pressure is 8 - 12 kpa, the crucible rotation speed is 10 - 15 rpm, the crystal rotation speed is 12 - 20 rpm, and the pulling speed is 1.2 - 0.4 mm / min.

[0070] Specifically, only by adjusting the crystal - growing process parameters such as the pulling speed, crystal rotation speed, and crucible rotation speed, the improvement of micro - defects is limited.

[0071] Example 1:

[0072] Using an 1806 single - crystal furnace, as used in ​The thermal field 10 shown grows 6-inch <111> heavily phosphorus-doped single crystals to improve the electrical uniformity of the terminal product. The seed crystal is <111> red phosphorus, the feeding amount is 60 kg, the doping amount is 280 g (resistivity range 0.015 - 0.018 Ω·cm). During the equal-diameter process: argon (50 - 55) slm, furnace pressure (8 - 12) kpa, crucible rotation (10 - 12) rpm, crystal rotation (12 - 20) rpm, pulling speed (1.2 - 0.9) mm / min, and crystal pulling is carried out to obtain the first crystal bar.

[0073] Comparative Example 1:

[0074] Using an 1806 single crystal furnace, use the 18-inch thermal field 20 as shown ​ to grow 6-inch <111> heavily phosphorus-doped single crystals. The thickness of the upper heat insulation material 420a of this thermal field is the same as that of the cooling upper heat insulation material 420 in Example 1, the thickness of the lower heat insulation material 320a is the same as that of the upper heat insulation material 420a, the straight section part of the thermal shield 411a is twice that of the straight section part in Example 1, there is no graphite part and hollow layer, and other parts are the same as the thermal field in Example 1. The seed crystal is <111> red phosphorus, the feeding amount is 60 kg, the doping amount is 280 g (resistivity range 0.015 - 0.018 Ω·cm). During the equal-diameter process: argon (50 - 55) slm, furnace pressure (8 - 12) kpa, crucible rotation (10 - 12) rpm, crystal rotation (12 - 20) rpm, pulling speed (1.2 - 0.9) mm / min, and crystal pulling is carried out to obtain the second crystal bar.

[0075] Comparative Example 2:

[0076] Using an 1806 single crystal furnace, use the 18-inch thermal field 30 as shown ​ to grow 6-inch <111> heavily phosphorus-doped single crystals. The upper heat insulation material 420b of this thermal field is twice the thickness of the cooling upper heat insulation material 420 in Example 1, the straight section part of the thermal shield 411b is twice that of the straight section part in Example 1, there is no graphite part and hollow layer, and other parts are the same as the thermal field in Example 1. The seed crystal is <111> red phosphorus, the feeding amount is 60 kg, the doping amount is 280 g (resistivity range 0.015 - 0.018 Ω·cm). During the equal-diameter process: argon (50 - 55) slm, furnace pressure (8 - 12) kpa, crucible rotation (10 - 12) rpm, crystal rotation (12 - 20) rpm, pulling speed (1.2 - 0.9) mm / min, and crystal pulling is carried out to obtain the third crystal bar.

[0077] Simulate the ​ , ​ , ​ thermal fields, and the results of temperature gradient and uniformity simulation are as shown ​ , 5 .

[0078] From​ , 5 It can be seen that in Comparative Example 1, by adjusting the upper heat insulation material and the lower heat insulation material, although there is a certain effect on improving the temperature gradient compared with the traditional heat field in Comparative Example 2, and the overall temperature gradient increases, the increase amplitude of the temperature gradient is limited. More importantly, the uniformity of the temperature is not significantly improved. In contrast, the present invention improves the upper heat insulation material for temperature reduction and the heat shield, which not only has a significant effect on improving the temperature gradient, but more importantly, significantly improves the uniformity of the temperature gradient at the solid-liquid interface. The better uniformity of the temperature gradient at the solid-liquid interface provides better growth conditions for crystal growth, and the uniformity of various characteristics of the growth interface will also be improved to a certain extent.

[0079] The first ingot, the second ingot, and the third ingot obtained in Example 1, Comparative Example 1, and Comparative Example 2 were respectively subjected to roller grinding, truncation, and slicing to obtain silicon wafers to be detected with equal diameters of 0 mm, 300 mm, 600 mm, 900 mm, and 1200 mm: The silicon wafers to be detected were heat-treated at a high temperature of 1100 °C for 2 h and then preferentially etched with Sirtl solution for 3 min, followed by macroscopic and microscopic inspections. As ​ shown, the results are shown in Table 1:

[0080] Table 1

[0081]

[0082]

[0083] From the above ​ and the results in Table 1, it can be seen that the first ingot obtained in Example 1 has the lowest occurrence rate of native microdefects, and thus the lowest microdefect density, the best quality result, no visible defects in the whole ingot, and is clean under microscopic inspection. At the same time, combined with the simulation results, it can be known that the overall temperature gradient of the heat field is the largest under this condition, and the improvement effect on microdefects is the most obvious, achieving the effect of eliminating the native microdefects in the whole ingot, improving the crystal quality while increasing the crystal qualification rate; and improving the uniformity of the performance of the end product.

[0084] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand the entire or partial processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A thermal field for improving the electrical property uniformity of a terminal product, comprising a quartz crucible, a heating component, and a heat insulation part. The heating component is located at the bottom and side of the quartz crucible. The heating component arranged on the side of the quartz crucible is located between the quartz crucible and the heat insulation part. The heat insulation part is located circumferentially around the quartz crucible, and is characterized in that: It further includes a temperature reduction component, and the temperature reduction component includes a temperature reduction heat shield part and an upper temperature reduction heat insulation material. A hollow layer is arranged at the lower part of the upper temperature reduction heat insulation material. The temperature reduction heat shield part is located above the quartz crucible, and the upper temperature reduction heat insulation material is located above the heat insulation material part. The upper end of the temperature reduction heat shield part overlaps with the upper part of the upper temperature reduction heat insulation material. The upper temperature reduction heat insulation material is assembled with the heat insulation material part to increase the temperature gradient, shorten the residence time of the crystal bar at 800°C - 1100°C, and reduce the microdefect density; The height of the hollow layer is 1 / 4 - 1 / 2 of the height of the upper temperature reduction heat insulation material; The thickness of the upper temperature reduction heat insulation material is 15 - 20 mm.

2. The thermal field for improving the electrical property uniformity of the terminal product according to claim 1, characterized in that: The temperature reduction component further includes a graphite part, and the graphite part is assembled with the heat insulation material part and the upper temperature reduction heat insulation material to provide support for the upper temperature reduction heat insulation material and the heat insulation material part.

3. The thermal field for improving the electrical property uniformity of the terminal product as claimed in claim 1, wherein: The temperature reduction heat shield part includes: a heat shield, a lifting ring, and a support ring. The lifting ring is located on the support ring, the support ring is located on the upper temperature reduction heat insulation material, the upper part of the heat shield is connected to the heat shield lifting ring, the heat shield lifting ring overlaps on the support ring, and the support ring is embedded in the upper temperature reduction heat insulation material.

4. The thermal field for improving the electrical uniformity of the terminal product according to claim 3, wherein: The heat shield includes an inner heat shield, an outer heat shield, and a heat shield heat insulation material. The inner heat shield is sleeved inside the outer heat shield, and the heat shield heat insulation material is filled between the inner heat shield and the outer heat shield.

5. The thermal field for improving the electrical uniformity of the terminal product according to claim 1, characterized in that: The heat insulation material part includes a middle heat insulation material and a lower heat insulation material. The upper temperature reduction heat insulation material, the middle heat insulation material, and the lower heat insulation material are arranged in sequence from top to bottom. The bottom of the upper heat insulation material is assembled with one end of the middle heat insulation material, and the other end of the middle heat insulation material is assembled with the lower heat insulation material.

6. The thermal field for improving the electrical property uniformity of the terminal product according to claim 1, wherein: The heating component includes a bottom heater and a side heater. The bottom heater is located at the bottom of the quartz crucible, and the side heater is located between the quartz crucible and the heat insulation material part to heat the quartz crucible.

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