CN115074830A - Method for prolonging service life of czochralski monocrystalline quartz crucible and crucible structure - Google Patents

Abstract

The invention specifically relates to the technical field of Czochralski monocrystalline silicon, in particular to a method and a crucible structure for improving the service life of a Czochralski monocrystalline quartz crucible. The technical problem to be solved is that the quartz crucible is easily deformed when a plurality of single crystal silicon rods are straightened. The technical scheme adopted is: a crucible structure for improving the service life of a Czochralski single crystal quartz crucible, comprising: a quartz crucible arranged on the inner side for containing molten silicon and a first crucible arranged on the outer side for supporting the quartz crucible , characterized in that a gap is left between the outer side of the quartz crucible and the inner side of the first crucible, and the first gap is filled with high-purity quartz sand, and the high-purity quartz sand is used to block the quartz crucible and the outer side under high temperature. When the first crucible reacts, the present invention can achieve protection by filling the first gap between the quartz crucible and the first crucible with high-purity quartz sand to change the original direct contact between the quartz crucible and the first crucible into indirect contact. The purpose of the outer layer of the quartz crucible.

Description

A method and crucible structure for improving the service life of Czochralski single crystal quartz crucible

technical field

The invention belongs to the technical field of Czochralski monocrystalline silicon, and in particular relates to a method and a crucible structure for improving the service life of a Czochralski monocrystalline quartz crucible.

Background technique

In the production process of single crystal silicon wafers, quartz crucibles are the key components of photovoltaic single crystal furnaces, and are consumable vessels for pulling large-diameter single crystal silicon. Based on the requirements of the purity of single crystal silicon wafers, the quartz crucible is scrapped after one or several times of heating and pulling, and a new quartz crucible needs to be purchased for the next crystal pulling, so it has strong consumables in the single crystal silicon industry chain. attribute characteristics.

Quartz crucible is a container for melting silicon in the process of single crystal silicon preparation. In Czochralski monocrystalline silicon, the one-time consumption of the quartz crucible and the time-consuming disassembly and assembly of the furnace account for a relatively high proportion of the cost. Under the traditional Czochralski method, the quartz crucible can only be used once, and only one crystal rod can be produced at a time. The continuous Czochralski method can continuously feed the quartz crucible during the crystal pulling process, and continuously produce multiple new crystal rods, which puts forward higher requirements on the life of the quartz crucible. Increasing the service time of the quartz crucible can maximize the utilization rate of the quartz crucible, greatly improve the production efficiency and reduce the manufacturing cost of single crystal silicon wafers. However, quartz crucibles have crystals that tend to become silicon dioxide at high temperatures, which is commonly referred to as "devitrification". Devitrification usually occurs on the surface of quartz crucibles. In daily use, we can find that quartz crucibles have both inside and outside. Devitrification phenomenon, external devitrification will reduce the original thickness of the quartz crucible, and the crucible with reduced strength is easy to cause deformation.

SUMMARY OF THE INVENTION

The invention overcomes the deficiencies in the prior art, and provides a method and a crucible structure for improving the service life of a Czochralski single crystal quartz crucible.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A crucible structure for improving the service life of a Czochralski single crystal quartz crucible, comprising: a quartz crucible arranged on the inner side for holding molten silicon and a first crucible arranged on the outer side for supporting the quartz crucible, characterized in that the There is a gap between the outside of the quartz crucible and the inside of the first crucible, and the first gap is filled with high-purity quartz sand, which is used to prevent the quartz crucible from reacting with the outside first crucible at high temperature.

Further, the mesh number of the high-purity quartz sand is 80-140 mesh, and the content of SiO ₂ is not less than 99.5%.

Further, the quartz crucible includes an inner coating layer, a transparent layer and a bubble layer from the inside to the outside, and the inner coating layer is a coating formed by spraying a barium hydroxide solution.

Further, the first crucible is a detachable structure, and the first crucible is a crucible made of graphite/carbon carbon.

Further, the first crucible includes a disc-shaped crucible tray and an annular crucible side wall, the center of the upper end of the crucible tray is provided with a positioning protrusion with a circular cross-section, and the crucible side wall includes a straight wall. The lower end of the straight wall portion is integrally formed with a curved portion, and the curved portion extends toward the center of the circle to form a positioning ring matched with the positioning protrusion.

Further, the crucible tray and the positioning protrusion are integrally formed or detachably connected.

Further, the width of the first gap is 2˜4 mm.

The present invention also provides a Czochralski single crystal furnace, and the Czochralski single crystal furnace adopts the above-mentioned crucible structure.

The invention also provides a method for improving the service life of a Czochralski single crystal quartz crucible. The quartz crucible is blocked from reacting with the graphite/carbon-carbon material crucible on the outside under high temperature; the thickness of filling high-purity quartz sand is 2-4 mm.

The invention also provides a method for preparing a crucible structure for improving the service life of a Czochralski single crystal quartz crucible, which is characterized by comprising the following steps: installing a fixed crucible tray; Lay 2-4mm high-purity quartz sand on the upper end of the carbon-carbon crucible tray; place the quartz crucible inside the graphite/carbon-carbon crucible to ensure that the gap between the outer wall of the quartz crucible and the inner wall of the graphite/carbon-carbon crucible is 2-4mm; High-purity quartz sand with a mesh number of 80-140 is added to the gap between the carbon-carbon crucibles.

Compared with the prior art, the present invention has the following beneficial effects.

In the present invention, by filling the first gap between the quartz crucible and the first crucible with high-purity quartz sand, the original direct contact between the quartz crucible and the first crucible is changed to indirect contact, because the high-purity quartz sand is used for the manufacture of quartz crucibles. The characteristics of the two are the same. When the graphite/carbon-carbon crucible is low in purity or contaminated, the high-purity quartz sand filled in the middle of it reacts with the graphite/carbon-carbon crucible to become silica. Crystal, high-purity quartz sand blocks the reaction between the quartz crucible and the outer graphite/carbon-carbon material crucible at high temperature, so as to achieve the purpose of protecting the outer layer of the quartz crucible.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

FIG. 1 is a schematic structural diagram of an implementation of the present invention.

FIG. 2 is a schematic structural diagram of the second embodiment of the present invention.

FIG. 3 is an enlarged schematic diagram of part A of the present invention.

In the figure: 10 is the quartz crucible, 20 is the first crucible, 210 is the side wall of the crucible, 220 is the crucible tray, 230 is the positioning protrusion, 240 is the positioning ring, 30 is the first gap, and 40 is the high-purity quartz sand.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

As shown in Figures 1-3, the present invention provides a crucible structure for improving the service life of a Czochralski single crystal quartz crucible. The crucible structure includes three layers, the outer layer is a first crucible 20 made of graphite/carbon carbon material, the inner The layer is a quartz crucible 10 , a first gap 30 is provided between the outer layer and the inner layer, and the first gap 30 is filled with high-purity quartz sand.

The quartz crucible 10 is a container for melting silicon during the preparation of single crystal silicon, and the inside is filled with molten silicon. The quartz crucible 10 is rigid under normal conditions, but will soften when the temperature reaches about 1600 degrees Celsius and cannot carry the molten silicon inside. Therefore, the quartz crucible 10 is rigid. The outside of the crucible 10 will be supported by a graphite/carbon-carbon crucible.

The quartz crucible 10 has crystals that tend to become silicon dioxide at high temperatures. This process is called recrystallization, also called "devitrification", and often called "devitrification". Devitrification usually occurs in the quartz crucible 10. In daily use, we can find that the inner and outer layers of the quartz crucible 10 have devitrification, and the degree of devitrification will also vary due to different reasons for devitrification. Devitrification will reduce the original thickness of the quartz crucible 10, and the crucible with reduced strength will easily cause deformation. The quartz crucible 10 ruptures and leaks silicon because it cannot withstand the pressure of the molten silicon, resulting in property damage and personal injury. Under the traditional Czochralski method, the quartz crucible is only used once, and only one crystal rod can be produced at a time, so the life expectancy of the quartz crucible 10 is not high. In the continuous Czochralski method, material can be continuously fed into the quartz crucible 10 during the crystal pulling process, and multiple new crystal rods can be continuously produced, which puts forward higher requirements on the service life of the quartz crucible 10 .

Quartz crucible crystallization is divided into internal crystallization and external crystallization. The main reason for external crystallization is that the graphite/carbon-carbon material crucible in direct contact with the outside itself has low purity or is contaminated, and it reacts with the outer quartz crucible 10 to cause quartz The outer layer of the crucible 10 is devitrified, which will accelerate the devitrification of the outer layer of the quartz crucible 10 , thereby reducing the service life of the quartz crucible 10 . Due to the defects of the Czochralski method, it is inevitable that the graphite/carbon-carbon crucible will be contaminated every time it is used.

By filling the high-purity quartz sand 40, the original direct contact is changed to indirect contact, because the high-purity quartz sand 40 is the raw material for making the quartz crucible, and the characteristics of the two are the same. When used, the high-purity quartz sand 40 filled in the middle reacts with the graphite/carbon-carbon material crucible to become silicon dioxide crystals, and the high-purity quartz sand 40 blocks the quartz crucible 10 and the outer graphite/carbon-carbon material under high temperature. The crucible reacts to protect the outer layer of the quartz crucible.

The content of SiO ₂ in the high-purity quartz sand 40 is not less than 99.5%, and the mesh number requires 80-140 mesh. If it is too large, the tiny gap between the quartz sand is too large, which is effective for improving the service life of the quartz crucible 10. If it is too small, it is too small. It is dense and affects the uniformity of heat in the thermal field. After experiments, when the mesh number of high-purity quartz sand 40 is 80-140 mesh, and the thickness is 2-4mm, when the 36-inch single crystal silicon rod is straightened, the service life can be increased from 300 hours to 400 hours, from 6 straightened to 8 straightened in one oven.

The quartz crucible 10 is an integrally formed bowl-shaped structure with an open upper end. The quartz crucible includes an inner layer and an outer layer. The inner layer is a transparent layer with low bubble content. The inner layer is coated with a barium coating. To a certain extent, the rupture of the bubble composite layer is prevented, so as to avoid the bubble rupture and escape from reacting with the inner surface of the quartz crucible 10, and a layer of dense and tiny cristobalite crystals can be formed on the wall of the quartz crucible, which can increase the strength of the quartz crucible. The quartz crucible 10 has the anti-deformation ability and heat radiation efficiency; the outer layer is a bubble composite layer, and the bubble content is relatively high, which can keep heat and ensure uniform heat transfer.

The graphite/carbon-carbon crucible is in the shape of a bowl as a whole, the upper end of which is open, and is arranged outside the quartz crucible 10 . The graphite/carbon-carbon crucible is a detachable split structure, a disc-shaped crucible tray 220 and an annular crucible side wall 210, and a positioning protrusion 230 with a circular cross-section is arranged at the center of the upper end of the crucible tray 220 to locate The upper end of the protrusion 230 is small and the lower end is large, and the upper end of the positioning protrusion 230 has a downwardly concave arc surface, and the concave arc surface can assist the positioning of the quartz crucible 10 to ensure the quartz crucible 10 and the graphite/carbon carbon. Coaxial of the crucible. The crucible side wall 210 includes a straight wall portion, and the lower end of the straight wall portion is integrally formed with a curved portion. The curved portion extends to the center of the circle to form a positioning ring 240. 230 to match.

In the first embodiment, as shown in FIG. 1 , it is a 32-inch monocrystalline silicon graphite/carbon-carbon crucible, the crucible tray 220 and the positioning protrusion 230 are integrally formed, and the diameter of the positioning protrusion 230 is less than 0.5 times that of the crucible tray 220. outer diameter, and the upper end of the crucible tray 220 is also a concave arc surface, the lower end of the curved portion of the crucible side wall 210 is placed on the upper end of the crucible tray 220, and is positioned by the positioning ring 240 and the positioning protrusion 230 to ensure the crucible side wall 210 Concentric with crucible tray 220 .

In the second embodiment, as shown in FIG. 2 , it is a 36-inch monocrystalline silicon graphite/carbon-carbon crucible, the crucible tray 220 and the positioning protrusion 230 are provided separately, and the diameter of the positioning protrusion 230 is slightly smaller than that of the crucible tray 220 Outer diameter, the lower end of the crucible side wall 210 is placed on the upper end of the crucible tray 220, and the positioning ring 240 cooperates with the positioning protrusion 230 to ensure that the crucible side wall 210 and the crucible tray 220 are concentric.

In the two embodiments, the inner diameter of the crucible side wall 210 is H, and the outer diameter of the quartz crucible 10 is H-(4-8) mm. The width of the first gap can be ensured to be 2 to 4 mm.

The invention also provides a Czochralski single crystal furnace, comprising a heater, an insulating layer, a graphite crucible, a quartz crucible, and a furnace wall, wherein the insulating layer and the heater are arranged inside the furnace wall, and the graphite crucible is fixed on the crucible tow bar, The crucible drag rod is connected with the central axis, the quartz crucible is placed in the graphite crucible, the high-purity quartz sand 40 is filled between the quartz crucible 10 and the graphite crucible, the molten silicon is prevented from being in the quartz crucible 10, and a heat screen is arranged above the molten silicon, The seed crystal is in contact with the molten silicon, and an exhaust hole is opened on the furnace wall.

The present invention also provides a method for improving the service life of a Czochralski single crystal quartz crucible. The method includes filling the gap between the outer wall of the quartz crucible 10 and the inner wall of the graphite/carbon-carbon material crucible with high-purity quartz sand 40 to separate the two. open, so as to prevent the quartz crucible 10 from reacting with the graphite/carbon-carbon material crucible on the outside at high temperature; wherein, the thickness of the filled high-purity quartz sand 40 is 2-4 mm.

The invention also provides a preparation method of a crucible structure for improving the service life of the Czochralski single crystal quartz crucible, and the method is as follows:

S1: Install and fix the crucible tray 220 to the upper end of the crucible drag rod;

S2: place the crucible side wall 210 concentrically on the upper end of the crucible tray 220;

S3: Lay 2-4mm high-purity quartz sand 40 on the upper end of the bottom wall of the graphite/carbon-carbon crucible;

S4: place the quartz crucible 10 inside the graphite/carbon-carbon crucible, adjust the position of the quartz crucible 10, ensure that the quartz crucible 10 is in the center of the graphite/carbon-carbon crucible, and ensure that the outer wall of the quartz crucible 10 and the inner wall of the graphite/carbon-carbon crucible can be ensured The gap is 2～4mm;

S5: Add high-purity quartz sand 40 with a mesh number of 80-140 to the gap between the quartz crucible 10 and the graphite/carbon-carbon crucible.

In the present invention, by filling the first gap between the quartz crucible and the first crucible with high-purity quartz sand, the original direct contact between the quartz crucible and the first crucible is changed to indirect contact, because the high-purity quartz sand is used for the manufacture of quartz crucibles. The characteristics of the two are the same. When the graphite/carbon-carbon crucible is low in purity or contaminated, the high-purity quartz sand filled in the middle of it reacts with the graphite/carbon-carbon crucible to become silica. Crystal, high-purity quartz sand blocks the reaction between the quartz crucible and the outer graphite/carbon-carbon material crucible at high temperature, so as to achieve the purpose of protecting the outer layer of the quartz crucible.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Those skilled in the art can make modifications or improvements to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. The crucible structure for prolonging the service life of the czochralski monocrystalline quartz crucible comprises a quartz crucible (10) arranged at the inner side for containing molten silicon and a first crucible (20) arranged at the outer side for supporting the quartz crucible (10), and is characterized in that a gap is reserved between the outer side of the quartz crucible (10) and the inner side of the first crucible (20), the first gap (30) is filled with high-purity quartz sand (40), and the high-purity quartz sand (40) is used for preventing the quartz crucible (10) from reacting with the first crucible (20) at the outer side at high temperature.

2. The crucible structure for improving the service life of a Czochralski single crystal quartz crucible as recited in claim 1,

the mesh number of the high-purity quartz sand (40) is 80-140 meshes, and SiO is ₂ The content of (A) is not less than 99.5%.

3. The crucible structure for improving the service life of the czochralski single crystal quartz crucible according to claim 1, wherein the quartz crucible (10) comprises an inner coating layer, a transparent layer and a bubble layer from the inside to the outside, and the inner coating layer is formed by spraying a barium hydroxide solution.

4. The crucible structure for improving the service life of the czochralski single crystal quartz crucible as claimed in claim 1, wherein the first crucible (20) is of a detachable structure, and the first crucible (20) is of a graphite/carbon material.

5. The crucible structure for prolonging the service life of the czochralski single crystal quartz crucible as claimed in claim 4, wherein the first crucible (20) comprises a disc-shaped crucible tray (220) and a circular crucible side wall (210), a positioning protrusion (230) with a circular cross section is arranged at the center of the upper end of the crucible tray (220), the crucible side wall (210) comprises a straight wall part, a bending part is integrally formed at the lower end of the straight wall part, and the bending part extends to the center of the circle to form a positioning ring (240) matched with the positioning protrusion (230).

6. The crucible structure for improving the service life of the czochralski single crystal quartz crucible as claimed in claim 5, wherein the crucible tray (220) is integrally formed with the positioning projection (230) or detachably connected thereto.

7. The crucible structure for improving the service life of the czochralski single crystal quartz crucible according to claim 4 or 5, wherein the width of the first gap (30) is 2-4 mm.

8. A Czochralski crystal growing furnace, wherein the Czochralski crystal growing furnace adopts the crucible structure as claimed in any one of claims 1 to 6.

9. A method for improving the service life of a Czochralski single crystal quartz crucible as claimed in any one of claims 2 to 7, wherein the gap between the outer wall of the quartz crucible (10) and the inner wall of the graphite/carbon crucible is filled with high purity quartz sand (40) to separate the outer wall from the graphite/carbon crucible to block the reaction of the quartz crucible (10) with the graphite/carbon crucible at a high temperature; the thickness of the filled high-purity quartz sand (40) is 2-4 mm.

10. A method of manufacturing a crucible structure for improving the service life of a Czochralski single crystal quartz crucible as claimed in any one of claims 4 to 7, comprising the steps of:

mounting and fixing a crucible tray (220);

placing the crucible side wall (210) concentrically on the upper end of the crucible tray (220);

paving 2-4 mm of high-purity quartz sand (40) at the upper end of the bottom wall of the graphite/carbon crucible;

placing the quartz crucible (10) into a graphite/carbon crucible, and ensuring that the gap between the outer wall of the quartz crucible (10) and the inner wall of the graphite/carbon crucible is 2-4 mm;

high-purity quartz sand (40) with the mesh number of 80-140 meshes is added to the gap between the quartz crucible (10) and the graphite/carbon crucible.

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