Silicon melt heavy phosphorus doping method and device for reducing drawing and releasing times

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a silicon melt phosphorus re-doping method and device for reducing the number of times of drainage and drainage, and after melting is completed, a molten silicon body is automatically stabilized; closing a magnetic field during first doping to prevent the magnetic field from inhibiting melt convection, and increasing the rotating speed of the pot to a first speed, increasing the argon flow to a first flow, increasing the power to a first power and increasing the furnace pressure to a first furnace pressure to accelerate melt convection; after doping is finished, a magnetic field is opened, temperature testing and crystal pulling are carried out, if shoulder broken edges and equal-diameter broken edges do not appear, crystal pulling is finished, if shoulder broken edges and equal-diameter broken edges appear, supplementary doping is carried out, the magnetic field is closed during supplementary doping, and the number of times of supplementary doping is not larger than 4; during supplementary doping, the rotating speed of the pot is increased to a second speed, the argon flow is increased to a second flow, the power is increased to a second power, and the furnace pressure is increased to a second furnace pressure, so that the convection effect of the silicon melt is remarkably improved, indissolvable substances formed by combining phosphorus and oxygen at high temperature are reduced, and the introduction and discharge times are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material preparation, and in particular relates to a method and a device for re-doping phosphorus into silicon melt for reducing the number of lead-in times. Background Art

[0002] Heavily phosphorus-doped semiconductor wafers are mainly used for power semiconductor substrates, which are mainly used in switch control, power conversion, motor drive and other aspects. At present, the power consumption requirements of power devices are getting lower and lower, so lower resistivity requirements are put forward for single crystal silicon substrates. The dopants of N-type silicon single crystals are mainly arsenic and antimony, but after the addition of arsenic and antimony elements, the resistivity of the resulting single crystal silicon does not meet the required requirements. Since phosphorus has a greater solid solubility in the silicon lattice, phosphorus doping can obtain single crystal silicon with lower resistivity. However, during the doping process, phosphorus elements and oxygen elements in the silicon melt are easily combined to form insoluble solid solutions. This solid solution is invisible to the naked eye, but it will cause shoulder broken edges and equal diameter broken edges during the crystal pulling process, which increases the number of lead-in times and leads to increased costs. Summary of the invention

[0003] In view of this, the present invention provides a method and apparatus for heavily doping silicon melt with phosphorus for reducing the number of drawing and releasing times, so as to solve the technical problem in the prior art that the phosphorus element and the oxygen element in the silicon melt are easily combined into an insoluble solid solution during the doping process, which will cause shoulder breakage and equal diameter breakage during the crystal pulling process, thereby increasing the number of drawing and releasing times and leading to increased costs.

[0004] To achieve the above objectives, this application adopts the following scheme:

[0005] A method for re-doping phosphorus in silicon melt for reducing the number of lead-in times comprises a doping step, wherein the doping step comprises:

[0006] S10. After the materials are fused, the molten silicon body automatically stabilizes;

[0007] S20. After the automatic stabilization is completed, the first doping is performed. During the first doping, the magnetic field is turned off to prevent the magnetic field from inhibiting the melt convection. At the same time, the pot rotation rate is increased to the first rate, the argon flow rate is increased to the first flow rate, the power is increased to the first power, and the furnace pressure is increased to the first furnace pressure to accelerate the melt convection;

[0008] S30. After the doping is completed, the magnetic field is turned on, and the temperature test and crystal pulling steps are performed. If there is no shoulder break or equal diameter break, the crystal pulling is completed. If there is shoulder break or equal diameter break, the step S40 is performed;

[0009] S40. Perform supplementary doping, turn off the magnetic field during supplementary doping, the number of supplementary doping is no more than 4 times, increase the pot rotation rate to the second rate, increase the argon flow rate to the second flow rate, increase the power to the second power, and increase the furnace pressure to the second furnace pressure during supplementary doping to accelerate melt convection, and repeat step S30.

[0010] Preferably, the first rate is the same as the second rate, both of which are 2 rpm to 4 rpm.

[0011] Preferably, the first flow rate is the same as the second flow rate, both of which are 155 slm to 165 slm.

[0012] Preferably, the first furnace pressure is the same as the second furnace pressure, both of which are 12 kPa to 16 kPa.

[0013] Preferably, the first power is the same as the second power, both of which are 90KW to 95KW.

[0014] Preferably, the mass ratio of the raw material to red phosphorus during the first doping is 1000:(6 to 8).

[0015] Preferably, the ratio of the raw material to red phosphorus during supplementary doping is 1000:(8 to 12).

[0016] A silicon melt re-doping phosphorus device comprises a control system for controlling a magnetic field switch, crucible rotation speed, gas flow, power and furnace pressure, and a corresponding actuator to execute any one of the above-mentioned silicon melt re-doping phosphorus methods for reducing the number of lead-in times.

[0017] The technical solution adopted in this application can achieve the following beneficial effects:

[0018] The invention provides a method for heavily doping silicon melt with phosphorus for reducing the number of lead-in times. During doping, the magnetic field is closed to prevent the magnetic field from inhibiting melt convection. Meanwhile, the pan rotation rate is increased, the argon flow rate is increased, the power is increased, the furnace pressure is increased, the convection of the melt is accelerated, and during doping, phosphorus and oxygen are reduced from combining at high temperature to form insoluble substances, thereby improving the survival rate of shoulder release and equal diameter, reducing the number of lead-in times, reducing the cost, and the resistivity of the prepared crystal rod is below 0.0013Ω·cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the doping process in the present invention;

[0020] Figure 2 A schematic diagram of the number of times of supplementary doping in the present invention;

[0021] Figure 3 It is a line graph of the resistivity of the single crystal silicon rod in Example 1 and Blank Example 1 of the present invention. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present application, the present application will be described more comprehensively below in conjunction with the accompanying drawings. And the preferred implementation of the present application is given. However, the present application can be implemented in many different forms and is not limited to the implementation described herein. On the contrary, the purpose of providing these implementations is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0024] A method for re-doping phosphorus into silicon melt to reduce the number of lead times, see Figure 1 and Figure 2 , comprising a doping step, the doping step comprising:

[0025] S10. After the materials are fused, the molten silicon body automatically stabilizes;

[0026] S20. After the automatic stabilization is completed, the first doping is performed. During the first doping, the magnetic field is turned off to prevent the magnetic field from inhibiting the melt convection. At the same time, the pot rotation rate is increased to the first rate, the argon flow rate is increased to the first flow rate, the power is increased to the first power, and the furnace pressure is increased to the first furnace pressure to accelerate the melt convection;

[0027] S30. After the doping is completed, the magnetic field is turned on, and the temperature test and crystal pulling steps are performed. If there is no shoulder break or equal diameter break, the crystal pulling is completed. If there is shoulder break or equal diameter break, the step S40 is performed;

[0028] S40. Perform supplementary doping, turn off the magnetic field during supplementary doping, the number of supplementary doping is no more than 4 times, increase the pot rotation rate to the second rate, increase the argon flow rate to the second flow rate, increase the power to the second power, and increase the furnace pressure to the second furnace pressure during supplementary doping to accelerate melt convection, and repeat step S30.

[0029] In this embodiment, since the segregation coefficient of phosphorus is 0.35, the smaller the segregation coefficient, the greater its saturated vapor pressure. In order to allow sufficient phosphorus to enter the silicon melt, it is necessary to dope after the silicon material is completely melted, that is, after the melting is completed, first, the magnetic field needs to be turned off to prevent the magnetic field from inhibiting melt convection. During the first doping, it is necessary to increase the pot rotation rate, increase the argon flow rate, increase the power, and increase the furnace pressure to accelerate the melt convection and prevent phosphorus from combining with oxygen to form an insoluble solid solution, which causes shoulder breakage and equal-diameter breakage during crystal induction. After the first doping is completed, the magnetic field is turned on to perform temperature testing and crystal pulling steps. After crystal pulling, if shoulder breakage and equal-diameter breakage do not occur, the doping step is completed. If shoulder breakage and equal-diameter breakage occur, supplementary doping is required. During supplementary doping, it is also necessary to turn off the magnetic field, increase the pot rotation rate, increase the argon flow rate, increase the power, and increase the furnace pressure to accelerate the melt convection. It should be noted that the number of supplementary doping does not exceed 4 times. If the number of supplementary doping exceeds 4 times, the resistivity of the prepared crystal rod is too high, the quality is poor, and it is not conducive to use.

[0030] The preferred doping method in this embodiment is quartz bell jar doping, and the specific process is: weigh the amount of red phosphorus to be doped in a nitrogen-protected glove box and put it into a quartz cup, hang the quartz cup in the quartz bell jar, and hang the quartz bell jar on the seed crystal rope and enter the furnace body, the seed crystal rope descends, and when the quartz bell jar approaches the silicon melt surface and begins to volatilize into the silicon melt, all the phosphorus volatilizes, the seed crystal rope is raised, and the quartz bell jar is taken out to complete the doping.

[0031] By adopting the method provided by the present invention, during doping, after the magnetic field is turned off, the magnetic field is prevented from inhibiting the convection of the melt, and the convection of the melt is accelerated by increasing the pot rotation rate, increasing the argon gas flow rate, increasing the power, and increasing the furnace pressure. During doping, the possibility of phosphorus and oxygen combining at high temperature to form insoluble substances is reduced, thereby improving the shoulder release and equal diameter survival rate, reducing the number of lead times, and the resistivity of the prepared crystal rod is below 0.0013Ω·cm.

[0032] Among them, the first rate is the same as the second rate, both of which are 2rmp to 4rmp, the pot speed rate is 1rmp to 2rmp when stable, and it is increased to 2rmp to 4rmp during doping; the first flow rate is the same as the second flow rate, both of which are 155slm to 165slm. Increasing the flow rate of argon gas can accelerate the convection of silicon melt on the one hand, and prevent the window from being blackened on the other hand; the first power is the same as the second power, both of which are 90KW to 95KW.

[0033] Preferably, the first furnace pressure is the same as the second furnace pressure, both of which are 12 kPa to 16 kPa. In some possible embodiments, the resistivity of the crystal rod prepared by heavy phosphorus doping is controlled by increasing the furnace pressure. However, the increase in furnace pressure may cause the angle of the APC valve to be too small, resulting in poor exhaust, further affecting crystal pulling, and the risk of cleaning the heavy phosphorus doped furnace is relatively large, and combustion is prone to occur. When the concentration of phosphorus oxide is high, explosion is prone to occur. Therefore, when using the doping step provided by the present method, the original pipeline is modified, and an explosion-proof valve and a manual valve are installed on the original pipeline to prevent the above-mentioned problems caused by excessive volatiles when red phosphorus is doped, resulting in poor exhaust. At the same time, the caliber of the APC valve is changed from the original 80 to a 50 caliber to ensure that the APC angle will not get stuck under high furnace pressure.

[0034] Specifically, the mass ratio of the raw material to the red phosphorus during the first doping is 1000:(6 to 8); and the mass ratio of the raw material to the red phosphorus during the supplementary doping is 1000:(8 to 12).

[0035] A silicon melt re-doping phosphorus device comprises a control system for controlling a magnetic field switch, crucible rotation speed, gas flow, power and furnace pressure, and a corresponding actuator to execute any one of the above-mentioned silicon melt re-doping phosphorus methods for reducing the number of lead-in times.

[0036] The following specific experimental examples are used to further illustrate the technical solutions and technical effects of the present invention. It should be noted that the following experimental examples are only for further explaining the present invention and do not limit the technical solutions of the present invention.

[0037] 1. Blank example 1

[0038] This blank example adopts the doping process existing in the prior art for doping, and the specific steps are: firstly, the material operation is carried out, and after the silicon material is completely melted, the silicon melt is allowed to automatically stabilize. After the automatic stabilization is completed, the first doping is started. After the first doping, the temperature test and crystal pulling steps are carried out. If the crystal rod does not have shoulder NG during crystal pulling, the process ends and a single crystal silicon rod is prepared. If the crystal rod has shoulder NG, additional doping is performed to prepare a single crystal silicon rod;

[0039] After the test, the number of lead-in times, the number of intact rods and the intact rod rate of the single crystal silicon rods in Blank Example 1 were counted, and the results are shown in Table 1.

[0040] 2. Example 1

[0041] This embodiment 1 adopts the silicon melt heavy doping phosphorus method provided by the present application for reducing the number of crystal pulling times to prepare crystal rods, and the number of pulling furnaces is 6 times. The specific steps are: first, the material operation is carried out. After the silicon material is completely melted, the magnetic field is turned off to allow the silicon melt to automatically stabilize. After the automatic stabilization is completed, the first doping is started. The mass ratio of the raw material to red phosphorus is 1000:7. At this time, the crucible rotation speed is adjusted from 1rmp when it is stabilized to 3rmp. The power is increased by 5KW on the basis of the crystal pulling power and adjusted to 95KW. The furnace pressure is 14kPa. At the same time, the flow rate of argon gas is adjusted to 160slm. After the first doping is completed, the magnetic field is turned on to perform temperature test and crystal pulling steps. If the crystal rod does not have shoulder release NG during crystal pulling, it is finished and a single crystal silicon rod is prepared. If the crystal rod has shoulder release NG, supplementary doping is performed. During supplementary doping, the mass ratio of the raw material to red phosphorus is 100:1, and a single crystal silicon rod is prepared;

[0042] After the test, the number of lead-in times, the number of intact rods and the intact rod rate of the single crystal silicon rods in Example 1 were counted, and the results are shown in Table 1.

[0043] 3. Comparative Example 1

[0044] The difference between this comparative example 1 and the above-mentioned embodiment 1 is that: during the initial doping and supplementary doping, the pot rotation rate, argon gas flow rate, power, and furnace pressure are not increased, and only the magnetic field is turned off to prepare a single crystal silicon rod;

[0045] After the test, the number of lead-in times, the number of intact rods and the intact rod rate of the single crystal silicon rods in Comparative Example 1 were counted, and the results are shown in Table 1.

[0046] 4. Comparative Example 2

[0047] The difference between this comparative example 2 and the above-mentioned embodiment 1 is that: during the initial doping and supplementary doping, the pot rotation rate, argon gas flow rate, power, and furnace pressure are increased, but the magnetic field is not turned off, and a single crystal silicon rod is prepared;

[0048] After the test, the number of lead-in times, the number of intact rods and the intact rod rate of the single crystal silicon rods in Comparative Example 2 were counted, and the results are shown in Table 1.

[0049] Table 1 Statistics of single crystal silicon rod data

[0050]

[0051]

[0052] It can be seen from the data in Table 1 above that the single crystal silicon rod prepared by the method provided in the present application adopted in Example 1 can effectively reduce the number of lead-in times compared with the single crystal silicon rod prepared by the doping method in the prior art, and the whole rod rate is increased by 33%. In Comparative Example 1, since the magnetic field is turned off during doping, although it can effectively prevent the magnetic field from inhibiting the melt convection, it will affect the whole rod rate of the crystal rod. Comparative Example 2 only adjusted the pot rotation, argon gas flow, power and furnace pressure, and it was found that the number of lead-in times of the crystal rod was still high.

[0053] In addition, the resistivity of the crystal rods prepared in the above Example 1 (after implementation) and Blank Example 1 (before implementation) was tested, and the test results are as follows: Figure 3 As shown by Figure 3 It can be seen that the resistivity of the crystal rods in Comparative Example 1 and Blank Example 1 is basically the same, without significant changes, and the resistivity is qualified, indicating that: while heavily doping molten silicon with phosphorus to prepare single crystal silicon rods with lower resistivity can reduce the number of lead-in times and improve the whole rod rate of the crystal rod.

[0054] In summary, during doping, it is necessary to increase the pot rotation rate, argon flow rate and power while turning off the magnetic field. The convection effect of the silicon melt is significantly improved, the distribution of phosphorus in the silicon melt is more uniform, and the doping effect is improved.

[0055] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for re-doping phosphorus into silicon melt for reducing the number of lead-in times, characterized in that: The method comprises a doping step, wherein the doping step comprises: S10. After the material is molten, the molten silicon body automatically stabilizes; S20. After the automatic stabilization is completed, the first doping is performed. During the first doping, the magnetic field is turned off to prevent the magnetic field from inhibiting the melt convection. At the same time, the pot rotation rate is increased to the first rate, the argon flow rate is increased to the first flow rate, the power is increased to the first power, and the furnace pressure is increased to the first furnace pressure to accelerate the melt convection; S30. After the doping is completed, the magnetic field is turned on, and the temperature test and crystal pulling steps are performed. If there is no shoulder break or equal diameter break, the crystal pulling is completed. If there is shoulder break or equal diameter break, the S40 step is performed; S40. Perform supplementary doping, during which the magnetic field is turned off, the number of supplementary doping is no more than 4 times, during which the pot rotation rate is increased to the second rate, the argon flow rate is increased to the second flow rate, the power is increased to the second power, and the furnace pressure is increased to the second furnace pressure to accelerate melt convection, and step S30 is repeated.

2. The method for re-doping phosphorus into silicon melt for reducing the number of draws according to claim 1, characterized in that: The first speed is the same as the second speed, both of which are 2 rpm to 4 rpm.

3. The silicon melt doping method for reducing the number of lead-in times according to claim 1, characterized in that: The first flow rate is the same as the second flow rate, both of which are 155 slm to 165 slm.

4. The method for re-doping phosphorus into silicon melt for reducing the number of draws according to claim 1, characterized in that: The first furnace pressure is the same as the second furnace pressure, both of which are 12 kPa to 16 kPa.

5. The method for re-doping phosphorus into silicon melt for reducing the number of draws according to claim 1, characterized in that: The first power is the same as the second power, both of which are 90KW to 95KW.

6. The method for re-doping phosphorus into silicon melt for reducing the number of draws according to claim 1, characterized in that: The mass ratio of the raw material to red phosphorus during the first doping is 1000:(6 to 8).

7. The method for re-doping phosphorus into silicon melt for reducing the number of draws according to claim 1, characterized in that: The ratio of raw material to red phosphorus during supplementary doping is 1000:(8 to 12).

8. A device for re-doping phosphorus into silicon melt, characterized in that: It includes a control system for controlling a magnetic field switch, crucible rotation speed, gas flow, power and furnace pressure, and a corresponding actuator to execute the method for heavily doping phosphorus in silicon melt for reducing the number of lead-in times as described in any one of claims 1 to 7.

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