Crystal pulling method for improving resistance uniformity in heavily doped surface

Abstract

The invention provides a crystal pulling method for improving resistance uniformity in a heavily-doped surface, and relates to the technical field of heavily-doped single crystal pulling methods, the crystal pulling method comprises a doping step, an oxidation step and a temperature testing step which are carried out in sequence, the oxidation step is added between the doping step and the temperature testing step, and after the doping is finished, the resistance uniformity in the heavily-doped surface is improved. Oxidation is performed for preset time under the preset crucible rotating speed, the preset argon flow and the preset furnace pressure, on one hand, the volatilization amount of the dopant is minimum, the dopant enters the surface of molten soup to the maximum extent, and then the resistivity requirement is guaranteed; and on the other hand, convection of the molten soup is improved, so that the dopant on the upper surface of the molten soup can be fully stirred after entering the molten soup, impurities are uniformly distributed in the molten soup, and the shouldering NG rate is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavily-doped single crystal pulling methods, and in particular relates to a crystal pulling method for improving the uniformity of heavily-doped in-plane resistance. Background Art

[0002] The impact of ultra-low resistance on power devices is very important. In power devices, resistance will cause energy loss and heat generation, affecting the efficiency and performance of the device. Therefore, reducing resistance can reduce energy loss and heat generation, and improve the efficiency and performance of power devices. Specifically, ultra-low resistance can bring the following effects: Improve efficiency: Resistance will cause energy loss during conversion, reducing efficiency. Reducing resistance can reduce this energy loss and improve the efficiency of power devices.

[0003] Reduce heat generation: Resistance will cause the device to generate heat, affecting the device's operating temperature and stability. Ultra-low resistance can reduce heat generation, help lower the device's operating temperature, and extend the device's life.

[0004] Improve response speed: In some power devices, resistance also affects the response speed of the device. Reducing resistance can increase the speed of signal transmission and improve the response speed of the device.

[0005] Therefore, reducing resistance can improve the efficiency, stability and response speed of the device, and is one of the important ways to improve the performance of power devices. Therefore, in order to reduce resistance, doping with dopants is necessary, but during the heavy doping process, dopants are easily volatilized at high temperatures, making the doping process difficult; in the growth process of CZ heavily doped arsenic single crystal silicon, in order to minimize the switching loss of the device and improve the efficiency of the device, the single crystal silicon substrate is required to have a lower resistivity, which corresponds to a higher doping concentration in the silicon melt; however, under such high concentration doping conditions, component overcooling is prone to occur during crystal growth, resulting in uneven distribution of dopants, affecting the electrical properties and quality of the crystal. Summary of the invention

[0006] In view of this, the present invention provides a crystal pulling method for improving the uniformity of heavily doped in-plane resistance.

[0007] The technical solution adopted by the present invention to solve its technical problem is: A crystal pulling method for improving the uniformity of heavily doped in-plane resistance comprises a doping step, a high temperature treatment step and a temperature test step which are performed in sequence. The high temperature treatment step is specifically as follows: after the doping step is completed, the crucible is cyclically rotated between low speed and high speed at a predetermined argon gas flow rate and a predetermined furnace pressure to make the dopant in the melt uniform, thereby making the in-plane resistance distribution of the crystal uniform.

[0008] Preferably, the predetermined argon gas flow rate is 140-160 slm, and the predetermined furnace pressure is 12-14 KPa.

[0009] Preferably, the crucible is cyclically rotated between low speed and high speed, specifically: the crucible is cyclically rotated at a low speed of 0.5-1 rpm and a high speed of 5-6 rpm.

[0010] Preferably, the crucible is cyclically rotated between low speed and high speed for 20-30 minutes.

[0011] Preferably, the switching time of the crucible for cyclic rotation between low speed and high speed is average.

[0012] Preferably, the temperature testing time in the temperature testing step is 3-4 hours.

[0013] Preferably, in the temperature testing step, the crucible rotation speed is 1-2 rpm, and the crystal rod rotation speed is 9-10 rpm.

[0014] Preferably, in the temperature testing step, the furnace pressure is 14-16 KPa, and the argon gas flow rate is 130-150 slm.

[0015] Preferably, in the doping step, the dopant is one of phosphorus, arsenic and antimony.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a crystal pulling method for improving the uniformity of heavily doped in-plane resistance, comprising a doping step, a high-temperature treatment step, and a temperature test step performed in sequence, wherein the high-temperature treatment step is specifically as follows: after the doping step is completed, the crucible is cyclically rotated between low speed and high speed under a predetermined argon flow rate and a predetermined furnace pressure; under a high temperature state, the crucible is cyclically rotated between low speed and high speed in conjunction with a predetermined argon flow rate and a predetermined furnace pressure to make the dopant more evenly mixed in the solution, so that the crystal is not prone to component overcooling during growth, the stability of the flat interface will not be destroyed, and the crystal growth interface will not be transformed into a cellular interface, thereby obtaining a heavily doped wafer with uniform in-plane resistivity distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of crucible cycle speed in high temperature treatment steps in Examples 1 and 2.

[0018] Figure 2 These are the in-plane distribution detection diagrams of the resistivity of the crystal rods of Examples 1 and 2 and Comparative Examples 1 and 2.

[0019] Figure 3 These are the resistivity detection diagrams of the crystal rods of Examples 1 and 2 and Comparative Examples 1 and 2. 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 crystal pulling method for improving the uniformity of heavily doped in-plane resistance comprises a doping step, a high temperature treatment step and a temperature test step which are performed in sequence. The high temperature treatment step is specifically as follows: after the doping step is completed, the crucible is cyclically rotated between low speed and high speed at a predetermined argon gas flow rate and a predetermined furnace pressure to make the dopant in the melt uniform, thereby making the in-plane resistance distribution of the crystal uniform.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a crystal pulling method for improving the uniformity of heavily doped in-plane resistance, comprising a doping step, a high-temperature treatment step, and a temperature test step performed in sequence, wherein the high-temperature treatment step is specifically as follows: after the doping step is completed, the crucible is cyclically rotated between low speed and high speed under a predetermined argon flow rate and a predetermined furnace pressure; under a high temperature state, the crucible is cyclically rotated between low speed and high speed in conjunction with a predetermined argon flow rate and a predetermined furnace pressure to make the dopant more evenly mixed in the solution, so that the crystal is not prone to component overcooling during growth, the stability of the flat interface will not be destroyed, and the crystal growth interface will not be transformed into a cellular interface, thereby obtaining a heavily doped wafer with uniform in-plane resistivity distribution.

[0023] Furthermore, the predetermined argon gas flow rate is 140-160 slm, and the predetermined furnace pressure is 12-14 Kpa, so that the dopant is mixed more evenly therein.

[0024] Furthermore, the crucible is cyclically rotated between low speed and high speed: the crucible is cyclically rotated at a low speed of 0.5-1 rpm and a high speed of 5-6 rpm. If the crucible rotates at a high speed or the crucible speed is suddenly too high, there is a risk that liquid overflows from the quartz crucible.

[0025] Specifically, the crucible is uniformly increased from 0.5-1 rpm to 5-6 rpm, and then uniformly decreased from 5-6 rpm to 0.5-1 rpm, and the rotation is repeated in this way.

[0026] Specifically, the crucibles rotate in the same direction.

[0027] Furthermore, the crucible is cyclically rotated between low speed and high speed for 20-30 minutes. If the time is too short, the dopant will not be uniform enough, and if the time is too long, the dopant will easily volatilize, affecting the resistivity.

[0028] Furthermore, the switching time of the crucible between the low speed and the high speed for cyclic rotation is averaged, so as to prevent the volatile dopant from volatilizing in the high temperature treatment step while ensuring the uniformity of the dopant.

[0029] Furthermore, the temperature testing time in the temperature testing step is 3-4 hours.

[0030] Furthermore, in the temperature testing step, the crucible speed is 1-2 rpm and the crystal rod speed is 9-10 rpm to reduce the resistivity.

[0031] Specifically, the crucible rotation direction in the temperature testing step is the same as the crucible rotation direction in the high temperature treatment step.

[0032] Furthermore, in the temperature test step, the furnace pressure is 14-16 Kpa and the argon flow rate is 140-160 slm to reduce the resistivity.

[0033] Furthermore, in the doping step, the dopant is one of phosphorus, arsenic and antimony.

[0034] The use of the present invention is described by the following examples. Embodiment 1:

[0035] Adopt 3212 type single crystal furnace, 32 inches hot field growth 12 inches <100> Heavily doped arsenic single crystal, feed amount 400kg, doping amount 3050g (resistivity range ≤0.003Ω·cm), Czochralski single crystal first put polysilicon raw materials into a quartz crucible, in a vacuum environment, use argon as a protective gas, heat the polysilicon to above 1420℃, and then maintain this temperature for a period of time to allow the silicon material to melt and change from solid to liquid. After the temperature stabilizes to the target temperature, the doping step is carried out to dope arsenic. After the doping is completed, the crucible is rotated at a low speed and a high speed at 1rpm and 5rpm within 20min under an argon flow rate of 150slm and a furnace pressure of 13Kpa. Figure 1 As shown, after the high temperature treatment step is completed, a temperature test step is carried out. The specific temperature test steps are: the intensity of the horizontal magnetic field is 3000GS, the crucible speed is 1rpm, the crystal rotation is 8rpm, the argon flow rate is 120slm, and the furnace pressure is 10Kpa. When the temperature is appropriate, the seed crystal is used to try to contact the liquid surface to observe the phenomenon to determine the temperature. Then, the necking, shoulder release, shoulder rotation, equal diameter, finishing, cooling, etc. are carried out to complete the crystal growth process to obtain a crystal rod. Embodiment 2:

[0036] Adopt 3212 type single crystal furnace, 32 inches hot field growth 12 inches <100> Heavily doped arsenic single crystal, feed amount 400kg, doping amount 3050g (resistivity range ≤0.003Ω·cm), Czochralski single crystal first put polysilicon raw materials into a quartz crucible, in a vacuum environment, use argon as a protective gas, heat the polysilicon to above 1420℃, and then maintain this temperature for a period of time to allow the silicon material to melt and change from solid to liquid. After the temperature stabilizes to the target temperature, the doping step is carried out to dope arsenic. After the doping is completed, the crucible is rotated at a low speed and a high speed at 1rpm and 5rpm within 20min under an argon flow rate of 150slm and a furnace pressure of 13Kpa. Figure 1 As shown, after the high temperature treatment step is completed, a temperature test step is carried out. The specific temperature test steps are: the intensity of the horizontal magnetic field is 3000GS, the crucible speed is 1rpm, the crystal rotation is 9rpm, the argon flow rate is 150slm, and the furnace pressure is 14Kpa. When the temperature is appropriate, the seed crystal is used to try to contact the liquid surface to observe the phenomenon to determine the temperature. Then, the necking, shoulder release, shoulder rotation, equal diameter, finishing, cooling, etc. are carried out to complete the crystal growth process to obtain a crystal rod.

[0037] Comparative Example 1: There is no high temperature treatment step. After the doping is completed, a temperature test step is performed. The temperature test step is the same as that in Example 2. The other steps are also the same as those in Example 2 to obtain a crystal rod.

[0038] Comparative Example 2: There is no high temperature treatment step. After the doping is completed, a temperature test step is performed. The temperature test step is the same as that in Example 1. The other steps are also the same as those in Example 1 to obtain a crystal rod.

[0039] The resistivity distribution in the surface of the crystal rods obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was tested, and the results were as follows: Figure 2 As shown, the resistivity of the crystal rod obtained above is tested, and the results are as follows Figure 3 shown.

[0040] Depend on Figure 2 It can be seen that in Examples 1 and 2, the high-temperature treatment step is performed between the doping step and the temperature test step, and the resistivity distribution in the surface is more uniform than that in Comparative Examples 1 and 2 where the high-temperature treatment step is not performed; and compared with Comparative Example 2, in Example 1, the resistivity is significantly reduced after the high-temperature treatment step is performed between the doping step and the temperature test step.

[0041] Depend on Figure 2 , 3 It can be seen that the resistivity of the crystal rod can be greatly reduced through the synergistic effect of the high temperature treatment step and the temperature test step.

[0042] 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 crystal pulling method for improving the uniformity of heavily doped in-plane resistance, characterized in that: The process comprises a doping step, a high temperature treatment step and a temperature test step which are performed in sequence. Specifically, the high temperature treatment step comprises: after the doping step is completed, the crucible is cyclically rotated between low speed and high speed under a predetermined argon flow rate and a predetermined furnace pressure to make the dopant in the melt uniform, thereby making the resistance distribution in the crystal surface uniform.

2. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: The predetermined argon gas flow rate is 140-160 slm, and the predetermined furnace pressure is 12-14 Kpa.

3. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: The cyclic rotation is carried out at a low speed of 0.5-1 rpm and a high speed of 5-6 rpm.

4. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: The crucible is cyclically rotated between low speed and high speed for 20-30 minutes.

5. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 4, characterized in that: The switching time of the crucible for cyclic rotation between low speed and high speed is average.

6. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: The temperature testing time in the temperature testing step is 3-4h.

7. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: In the temperature testing step, the crucible rotation speed is 1-2 rpm, and the crystal rod rotation speed is 9-10 rpm.

8. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: In the temperature test step, the furnace pressure is 14-16 Kpa, and the argon flow rate is 140-160 slm.

9. The crystal pulling method for improving the uniformity of heavily doped in-plane resistance according to claim 1, characterized in that: In the doping step, the dopant is one of phosphorus, arsenic and antimony.

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