Czochralski silicon thermal field insulation cylinder

Abstract

The invention discloses a Czochralski monocrystalline silicon thermal field thermal insulation cylinder, which belongs to the technical field of monocrystalline silicon production, and comprises an upper cylinder body and a lower cylinder body, the inner diameter of the upper barrel is larger than that of the lower barrel, and steps at the inner joint of the upper barrel and the lower barrel are streamlined. The upper end and the lower end of the inner wall of the heat preservation cylinder form rounding oblique angles; a plurality of diversion trenches are formed in the inner wall of the heat preservation cylinder from the upper end to the lower end. The invention can effectively solve the problems of low thermal utilization efficiency of the existing monocrystalline silicon thermal field, pollution of returned gas to silicon liquid, difficult crystallization caused by high oxygen content in crystals and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal silicon production, and in particular relates to a thermal field insulation cylinder for direct-pull single crystal silicon. Background Art

[0002] The production of single crystal silicon by the Czochralski method includes the process of melting the silicon material after it is hoisted into the quartz crucible, then feeding it twice, and then pulling it upward to produce N-type or P-type single crystal silicon rod products through the process of temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter, finishing, cyclic feeding, and stopping the furnace in sections. The components used in the whole process include single crystal furnace, crucible, crucible, support rod, insulation cylinder, heat shield, insulation felt, heater, gas guide cylinder, etc. These components together form a protective device to prevent heat loss and pollution of the thermal energy control field, referred to as the thermal field.

[0003] There are three main problems with the existing thermal field structure: First, the thermal insulation of carbon-carbon parts and graphite parts is poor. The main reason is that the thermal conductivity of carbon is relatively high, resulting in the thermal utilization rate of the single crystal furnace being only 40%, causing serious waste of heat energy.

[0004] Secondly, there is a right angle at the joint of the thermal field components. When the airflow flows through this place, it is easy to form a cyclone at the connection, causing airflow turbulence, easy to cause backflow, and pollute the silicone liquid.

[0005] Third, the oxygen content in the crystal is relatively high. In some previous cases, an insulation ring was added between the middle and lower insulation tubes to reduce the oxygen content in the crystal, but the effect was not good. The biggest problem was that crystallization was difficult. The main reason was that the insulation ring was made of carbon-carbon parts, and the thermal conductivity was still very high. Cyclones were easily formed at the joint corners. The airflow contained a large amount of impurity gases, which would cause the crystal to break when flowing into the silicon liquid, making crystallization difficult. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, the present invention proposes a thermal field insulation cylinder for CZ single crystal silicon.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions: A thermal field insulation cylinder for straight-pull single crystal silicon, the insulation cylinder comprises an upper cylinder and a lower cylinder; the inner diameter of the upper cylinder is larger than that of the lower cylinder, and the internal connection of the upper and lower cylinders is streamlined; the upper and lower ends of the inner wall of the insulation cylinder form chamfered angles; the inner wall of the insulation cylinder is provided with a plurality of guide grooves from the upper end to the lower end.

[0008] Furthermore, the upper cylinder and the lower cylinder are integrally formed.

[0009] Furthermore, the insulation tube is made of carbon-carbon parts, graphite or high-temperature resistant ceramics.

[0010] Furthermore, a plurality of mounting grooves are provided at the lower end of the heat preservation tube.

[0011] Furthermore, the number of the installation slots is 4.

[0012] Through the above technical solution, the present invention can at least achieve the following beneficial effects: First, the top of the insulation cylinder has a rounded bevel, which can reduce the vortex formed by the airflow compared to the right angle, prevent the oxide gas from being returned to the crucible by the vortex and dissolving into the silicon liquid, increase the oxygen content of the single crystal silicon rod, and even cause the crystal to break, making it difficult to crystallize, thereby improving the crystallization rate; Second, the steps at the internal connection of the upper and lower cylinders are streamlined. The main function of the steps is to guide the flow and insulate the heat to reduce energy consumption. Since the heating coil of the main heater is mainly in the upper insulation cylinder, its function is to heat and melt the solid silicon material into liquid silicon material. During the crystal pulling process, the heat energy emitted by the main heater should be at the solid-liquid interface as much as possible to prevent heat from being lost to the non-equal diameter interface area below the solid-liquid interface. The step is inclined rather than horizontal, and its purpose is to ensure that the airflow flows stably and smoothly into the air guide cylinder at the bottom of the furnace to prevent the formation of vortices at the steps of the middle and lower insulation cylinders. The protruding steps at the bottom of the lower insulation cylinder are also designed for the same purpose. Third, on the inner walls of the upper and lower insulation cylinders, there are multiple guide grooves evenly distributed in a close circle from top to bottom. The purpose is to accelerate the discharge efficiency of the oxides produced in the crucible. The grooves connect the upper edge of the main heater and the inlet of the gas guide cylinder at the bottom of the furnace from top to bottom, which can greatly accelerate the discharge of oxides and impurity gases, thereby reducing the oxygen content in the crucible. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the heat preservation cylinder in the present invention; Figure 2 It is a schematic diagram of the structure of the heat preservation tube after half of it is removed vertically in the present invention; Figure 3 It is a schematic diagram of the connection structure between the heat preservation tube and other thermal field elements in the present invention.

[0014] In the figure, 1, upper cylinder; 2, lower cylinder; 3, step; 4, chamfered angle; 5, guide groove; 6, mounting groove; 7, drag rod; 8, tray; 10, pot bang; 9, pot support; 11, crucible; 12, main heater ring. DETAILED DESCRIPTION

[0015] Unless otherwise specified, the materials and reagents used in the present invention are commercially available.

[0016] Embodiment, a CZ single crystal silicon thermal field insulation cylinder, referring to the attached Figure 1-3The insulation cylinder comprises an upper cylinder 1 and a lower cylinder 2; the inner diameter of the upper cylinder 1 is larger than that of the lower cylinder 2, and the step 3 at the internal connection between the upper and lower cylinders 2 is streamlined; the upper and lower ends of the inner wall of the insulation cylinder form a chamfered angle 4; a plurality of guide grooves 5 are opened on the inner wall of the insulation cylinder from the upper end to the lower end.

[0017] Through the above settings, when the thermal insulation tube is in use, the installation and use diagram is as shown in the attached Figure 3 As shown, the quartz crucible 11 is installed in the insulation cylinder through the tow rod 7, the tray 8, the pot 10 and the pot support 9. The main heater ring 12 is used to heat the metal silicon in the quartz crucible 11. The distance between the main heater ring 12 and the top of the upper cylinder 1 is greater than 18mm. The insulation cylinder has the function of heat insulation. The connection between the upper cylinder 1 and the lower cylinder 2 is provided with a streamlined step 3, which can hinder the downward transfer of the heat emitted by the main heater to a certain extent, so that most of the heat is stored in the upper insulation cylinder, and then the heat is transferred to the crucible 11 through thermal radiation to heat the single crystal silicon, thereby reducing heat loss and power consumption. Most of the heat energy of the main heater is isolated to the inside of the middle insulation cylinder, and the reaction temperature of the middle and lower parts of the crucible 11 is effectively reduced, that is, the reaction temperature of the oxide generation is reduced, the oxygen impurities generated in the silicon liquid in the crucible 11 are reduced, and the oxides and carbon impurities above the solid-liquid interface are reduced. The top and bottom of the insulation tube are both provided with circular chamfers to prevent the argon gas from passing through the heater and forming vortices at the top and bottom of the insulation tube, and the additional guide groove 5 inside directly stabilizes the direction of the airflow and accelerates the transmission speed of the airflow, so that the impurity gas and dust particles on the solid-liquid surface and around the heater are quickly carried away, reducing the possibility of silicon liquid contamination and edge breakage, and improving the survival rate of the crystal.

[0018] In one embodiment, referring to the attached Figure 1-3 , the upper cylinder 1 and the lower cylinder 2 are integrally formed.

[0019] In one embodiment, referring to the attached Figure 1-3 The insulation tube is made of carbon-carbon parts, graphite or high-temperature resistant ceramics, preferably graphite, which has the advantage of low cost.

[0020] In one embodiment, referring to the attached Figure 1-3 The lower end of the insulation tube is provided with a plurality of mounting grooves 6. The mounting grooves 6 are used to mount the main heater foot plate, otherwise the bottom of the foot plate will hit the bottom bend of the insulation tube. In one embodiment, referring to the attached Figure 1-3 The number of the mounting grooves 6 is 4 and they are arranged at equal intervals at the lower end of the heat preservation tube.

[0021] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A CZ single crystal silicon thermal field insulation cylinder, characterized in that: The heat preservation cylinder comprises an upper cylinder and a lower cylinder; the inner diameter of the upper cylinder is larger than that of the lower cylinder, and the internal connection of the upper and lower cylinders is streamlined; the upper and lower ends of the inner wall of the heat preservation cylinder form chamfered angles; the inner wall of the heat preservation cylinder is provided with a plurality of guide grooves from the upper end to the lower end.

2. The CZ-type single crystal silicon thermal field insulation cylinder according to claim 1, characterized in that The upper cylinder and the lower cylinder are integrally formed.

3. The CZ-type single crystal silicon thermal field insulation cylinder according to claim 1, characterized in that: The insulation cylinder is made of carbon-carbon parts, graphite or high-temperature resistant ceramics.

4. The CZ-type single crystal silicon thermal field insulation cylinder according to claim 1, characterized in that: A plurality of mounting grooves are provided at the lower end of the heat preservation cylinder.

5. The CZ-type single crystal silicon thermal field insulation cylinder according to claim 4, characterized in that: The number of the installation slots is 4.

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