Crystal pulling method for reducing carbon content of crystal

Abstract

The invention provides a crystal pulling method for reducing the carbon content of crystals, and relates to the technical field of single crystal Czochralski methods, a predetermined guide cylinder is adopted for crystal pulling, and on the premise of ensuring the thermal stability and mechanical strength of a thermal field, on one hand, generation of C at a high temperature is reduced, so that CO generated by chemical reaction of C and oxygen in inert gas in a furnace is reduced; on the other hand, CO generated by reaction of C and the quartz crucible is reduced; and taking away the generated CO through preset furnace pressure and preset argon flow in the equal-diameter process so as to reduce the amount of CO entering the silicon solution, thereby reducing the carbon content in the silicon single crystal.

Description

Technical Field

[0001] The present invention belongs to the technical field of Czochralski single crystal pulling methods, and in particular relates to a crystal pulling method for reducing the carbon content of a crystal. Background Art

[0002] Carbon content refers to the amount of carbon present in chip materials. Carbon can exist in chip materials in different forms, such as impurities, impurity atoms, or lattice defects. The impact of carbon content on logic chips can be reflected in the following aspects: Electrical properties: The presence of carbon may change the conductivity of chip materials and the rate of carrier migration, thus affecting the electrical properties of logic chips. High carbon content may lead to a decrease in electron mobility, affecting device performance and response speed.

[0003] Thermal properties: The presence of carbon affects the thermal conductivity and thermal stability of the material. In logic chips, thermal management is very important, and excessive carbon content may cause uneven heat scattering or hot spots, affecting the stability and reliability of the chip.

[0004] Device reliability: The presence of carbon may lead to the formation of crystal defects or electron traps, affecting the reliability and life of the device. Especially under high temperature and high pressure, carbon may react with other elements, aggravating the damage and aging of the chip.

[0005] Process impact: Carbon may affect the stability and yield of the chip manufacturing process. Too high a carbon content may increase the difficulty of processing and affect the manufacturing cost and production efficiency of the device.

[0006] Optical properties: The presence of carbon may affect the optical properties of the chip, such as transmittance, reflectivity, etc. In optoelectronic devices, changes in carbon content may affect the optical performance and response speed of the device.

[0007] In order to reduce the impact of carbon content on logic chips, in the prior art, such as the Chinese invention with application number: 202211168934.7, a heating device and method that can effectively reduce the carbon impurity content in silicon wafers are disclosed. By arranging an exhaust pipe assembly on the insulation cover, when the insulation cover and the quartz crucible are in a closed state to heat the molten silicon, the volatilization to the upper part of the crystal-turned silicon ingot is not conducive to entering the lateral exhaust pipe for discharge, so that the rising carbon impurities are easy to enter the vertical exhaust pipe and enter the slag collecting box or enter the slag collecting box through the horizontal connecting pipe, thereby discharging the carbon impurities located on the upper part of the crystal ingot and reducing the carbon impurity content on the surface of the crystal ingot; however, the above-mentioned prior art can only reduce the carbon content of molten silicon in the process of preparing the crystal ingot, and is not applicable to how to reduce the carbon content in the crystal during the direct pulling of single crystals. Therefore, it is necessary to explore a crystal pulling method for reducing the carbon content of the crystal. Summary of the invention

[0008] In view of this, the present invention provides a crystal pulling method for reducing the carbon content of a crystal.

[0009] The technical solution adopted by the present invention to solve its technical problem is: A crystal pulling method for reducing the carbon content of a crystal, which uses a predetermined guide tube to pull the crystal to reduce the generation of C and CO, and in the equal diameter process, a predetermined furnace pressure and a predetermined argon flow rate are used to remove the generated CO to reduce the carbon content in the crystal.

[0010] Preferably, the guide tube includes an outer guide tube, an inner guide tube, and a thermal insulation material. The inner guide tube is located at the upper part of the outer guide tube, the two ends of the outer guide tube are connected to the two ends of the inner guide tube, and the thermal insulation material is filled in the cavity between the outer guide tube and the inner guide tube.

[0011] Preferably, the inner guide tube is made of quartz.

[0012] Preferably, in the equal diameter process, the predetermined furnace pressure is 3-5 KPa, and the predetermined argon gas flow rate is 140-160 slm.

[0013] Preferably, during the equal diameter process, the strength of the horizontal magnetic field is 2500-3500 GS.

[0014] Preferably, during the equal diameter process, the crystal rod rotation speed is 8-12 rpm.

[0015] Preferably, during the equal diameter process, the crucible rotation speed is 1-2.5 rpm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a crystal pulling method for reducing the carbon content of a crystal. The method adopts a predetermined guide tube to pull the crystal. On the one hand, the generation of C at high temperature is reduced, thereby reducing the chemical reaction between C and oxygen in the inert gas in the furnace to generate CO; on the other hand, the reaction between C and a quartz crucible to generate CO is reduced; and then in the equal diameter process, the generated CO is taken away by a predetermined furnace pressure and a predetermined argon gas flow rate to reduce the amount of CO entering a silicon solution, thereby reducing the carbon content in the silicon single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of the predetermined guide tube.

[0018] Figure 2 The carbon content detection results of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown.

[0019] In the figure: a guide tube 10, an outer guide tube 100, an inner guide tube 200, and a thermal insulation material 300. 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 reducing the carbon content of a crystal, which uses a predetermined guide tube to pull the crystal to reduce the generation of C and CO, and in the equal diameter process, a predetermined furnace pressure and a predetermined argon flow rate are used to remove the generated CO to reduce the carbon content in the crystal.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a crystal pulling method for reducing the carbon content of a crystal. Under the condition of ensuring the thermal stability of the thermal field and the mechanical strength, a predetermined guide tube is used for crystal pulling. On the one hand, the generation of C at high temperature is reduced, thereby reducing the chemical reaction between C and oxygen in the inert gas in the furnace to generate CO; on the other hand, the reaction between C and a quartz crucible to generate CO is reduced; and then in the equal diameter process, the generated CO is taken away by a predetermined furnace pressure and a predetermined argon flow rate, so as to reduce the amount of CO entering into a silicon solution, thereby reducing the carbon content in the silicon single crystal.

[0023] Furthermore, the guide tube 10 includes an outer guide tube 100, an inner guide tube 200, and a thermal insulation material 300. The inner guide tube 200 is located at the upper part of the outer guide tube 100, and the two ends of the outer guide tube 100 are connected to the two ends of the inner guide tube 200. The thermal insulation material 300 is filled in the cavity between the outer guide tube 100 and the inner guide tube 200.

[0024] Furthermore, the inner guide tube 200 is made of quartz material, and the outer guide tube 100 is made of graphite material, so as to reduce the generation of C content.

[0025] Furthermore, during the equal-diameter process, the predetermined furnace pressure is 3-5 KPa, and the predetermined argon flow rate is 140-160 slm to carry away CO, and the predetermined furnace pressure needs to be stabilized within the above range to prevent the vacuum pump from reaching its limit and causing the furnace pressure to fluctuate. If the argon flow rate is larger, it will make crystal pulling more difficult.

[0026] Furthermore, during the equal diameter process, the intensity of the horizontal magnetic field is 2500-3500GS, so that the temperature in the furnace will not be disturbed, and large fluctuations in the liquid surface temperature will not affect crystal pulling.

[0027] Furthermore, during the equal diameter process, the rotation speed of the crystal rod is 8-12 rpm to ensure that other qualities of the crystal rod do not change.

[0028] Furthermore, during the equal diameter process, the crucible rotation speed is 1-2.5 rpm to ensure that other qualities of the crystal rod do not change.

[0029] The use of the present invention is described by the following examples. Embodiment 1:

[0030] Adopt 3212 type single crystal furnace, 32 inches hot field growth 12 inches <100> Lightly boron-doped single crystal, feed amount 300kg, use as Figure 1 The predetermined guide tube 10 and the inner guide tube 200 are made of quartz. First, the polysilicon raw material is placed in a quartz crucible, and argon is used as a protective gas to heat the polysilicon to above 1420°C, so that the silicon material melts and the polysilicon changes from solid to liquid. Then, the necking, shouldering, shoulder rotation, equal diameter, tailing, cooling, etc. are performed to complete the crystal growth process. In the equal diameter process, the horizontal magnetic field strength is 3000 GS, the crystal rod speed is 10 rpm, the crucible speed is 1-2.5 rpm, the furnace pressure is 4 KPa, and the argon flow rate is 150 slm.

[0031] Comparative Example 1: During the equal diameter process, the horizontal magnetic field strength is 3000 GS, the crystal rod rotation speed is 10 rpm, the crucible rotation speed is 1-2.5 rpm, the furnace pressure is 8 KPa, the argon gas flow rate is 120 slm, and the rest are the same as in the first embodiment.

[0032] Comparative Example 2: The inner guide tube 200 is made of graphite, and the rest is the same as that of the first embodiment.

[0033] Comparative Example 3: The inner guide tube 200 is made of graphite. In the equal diameter process, the horizontal magnetic field strength is 3000 GS, the crystal rod speed is 10 rpm, the crucible speed is 1-2.5 rpm, the furnace pressure is 8 KPa, the argon flow rate is 120 slm, and the rest is the same as in the first embodiment.

[0034] The carbon content of the single crystal ingots obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was tested. The test results are as follows: Figure 2 shown.

[0035] Depend on Figure 2 It can be seen that the carbon content of the crystal rod pulled by Example 1 is greatly lower than the carbon content of the crystal rods pulled by Comparative Example 1, Comparative Example 2, and Comparative Example 3, and can reach below 0.03ppma. It can be seen from Example 1, Comparative Example 1, and Comparative Example 2 that by changing the material of the inner guide tube 200 and the parameters in the equal diameter process so that they can play a synergistic role, the carbon content in the crystal rod can be reduced.

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

Claims

1. A crystal pulling method for reducing the carbon content of a crystal, characterized in that: A predetermined guide tube is used for crystal pulling to reduce the generation of C and CO, and during the equal diameter process, the generated CO is taken away by a predetermined furnace pressure and a predetermined argon flow rate to reduce the carbon content in the crystal.

2. The crystal pulling method for reducing the carbon content of a crystal according to claim 1, characterized in that: The guide tube includes an outer guide tube, an inner guide tube, and a thermal insulation material. The inner guide tube is located at the upper part of the outer guide tube, the two ends of the outer guide tube are connected to the two ends of the inner guide tube, and the thermal insulation material is filled in the cavity between the outer guide tube and the inner guide tube.

3. The crystal pulling method for reducing the carbon content of a crystal according to claim 2, characterized in that: The inner guide tube is made of quartz material.

4. The crystal pulling method for reducing the carbon content of a crystal according to claim 1, characterized in that: During the equal diameter process, the predetermined furnace pressure is 3-5 KPa, and the predetermined argon gas flow rate is 140-160 slm.

5. The crystal pulling method for reducing the carbon content of a crystal according to claim 1, characterized in that: During the equal diameter process, the intensity of the horizontal magnetic field is 2500-3500 GS.

6. The crystal pulling method for reducing the carbon content of a crystal according to claim 1, characterized in that: During the equal diameter process, the crystal rod rotation speed is 8-12 rpm.

7. The crystal pulling method for reducing the carbon content of a crystal according to claim 1, characterized in that: During the equal diameter process, the crucible rotation speed is 1-2.5 rpm.

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