CN118184115A - Low-microbubble semiconductor-grade synthetic quartz crucible, preparation method thereof and monocrystalline silicon growth method - Google Patents
Low-microbubble semiconductor-grade synthetic quartz crucible, preparation method thereof and monocrystalline silicon growth method Download PDFInfo
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- CN118184115A CN118184115A CN202410601156.9A CN202410601156A CN118184115A CN 118184115 A CN118184115 A CN 118184115A CN 202410601156 A CN202410601156 A CN 202410601156A CN 118184115 A CN118184115 A CN 118184115A
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 118
- 239000010453 quartz Substances 0.000 title claims abstract description 81
- 238000000034 method Methods 0.000 title claims abstract description 43
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
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- 230000008018 melting Effects 0.000 claims abstract description 44
- 238000001816 cooling Methods 0.000 claims abstract description 35
- 238000002485 combustion reaction Methods 0.000 claims abstract description 30
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 25
- 239000010439 graphite Substances 0.000 claims abstract description 25
- 238000000465 moulding Methods 0.000 claims abstract description 11
- 239000007789 gas Substances 0.000 claims description 66
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 28
- 239000004065 semiconductor Substances 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 229910052757 nitrogen Inorganic materials 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 239000001307 helium Substances 0.000 claims description 11
- 229910052734 helium Inorganic materials 0.000 claims description 11
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims 1
- 229910001882 dioxygen Inorganic materials 0.000 claims 1
- 230000000052 comparative effect Effects 0.000 description 20
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000002679 ablation Methods 0.000 description 2
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 2
- 238000007790 scraping Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
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- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention provides a low-microbubble semiconductor-grade synthetic quartz crucible, a preparation method thereof and a monocrystalline silicon growth method, wherein the preparation method comprises the following steps: sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding; in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state. The preparation method of the synthetic quartz crucible effectively improves the quality of the quartz crucible, reduces pollution brought by the preparation process of the quartz crucible, and improves the quality of monocrystalline silicon products.
Description
Technical Field
The invention belongs to the field of monocrystalline silicon preparation, and relates to a low-microbubble semiconductor-grade synthetic quartz crucible, a preparation method thereof and a monocrystalline silicon growth method.
Background
Monocrystalline silicon as a starting material for the manufacture of most semiconductor electronic components is generally prepared by the so-called czochralski method ("CZ"). Using the CZ method, crystal growth is most commonly performed in a crystal pulling furnace, wherein polycrystalline silicon ("polysilicon") is charged into a crucible and melted by a heater surrounding the outer surface of the crucible sidewall. The seed crystal is contacted with molten silicon and a growing monocrystalline ingot is extracted by a crystal puller.
The crucibles used in conventional crystal pulling are generally composed of quartz because of its purity, temperature stability and chemical resistance. One method for manufacturing a quartz crucible is disclosed in U.S. patent No.4416680, in which a quartz feedstock is introduced into a rotating hollow mold. After the raw materials are introduced, a heat source such as an arc is introduced into the mold, which causes the quartz to melt. While heating, a vacuum is applied to the exterior of the mold during the continued rotation to draw out any interstitial gas in order to collapse the voids. Vacuum is maintained during melting and rotation. Thereafter, the finished crucible can be evacuated by replacing the vacuum with compressed air outside the mold. In this process, residual gases such as carbon, hydroxyl groups, etc. may lead to the formation of undesirable bubbles in the quartz glass.
During crystal growth, prolonged exposure of the crucible inner side walls to the high temperature silicon melt causes the silicon melt to react with the quartz crucible and cause dissolution of the inner surface of the crucible side walls. This exposes the bubbles in the crucible side walls to the molten silicon. As a result, the silicon melt continues to dissolve into the walls of the crucible and thus into the walls of the bubbles. At some point, the walls of the bubble are broken and the walls may collapse, with gas being released from the interior of the bubble and quartz particles being released from the crucible and/or the bubble side walls into the melt. In so doing, the particles may disrupt the monocrystalline structure, thereby limiting the yield of the crystal growth monocrystalline. Furthermore, the presence of bubble cavities or bubble voids along the inner surface of the crucible may be sites for gas nucleation. As the gas nucleates and grows into small bubbles, these bubbles may enter the growing silicon, causing the crystal to have voids, which are off specification. The reduction or elimination of bubbles in the crucible will ensure that voids in the crystal are minimized to achieve acceptable crystal performance within specification.
The preparation process of the quartz crucible for improving the micro-bubbles of the transparent layer comprises the following steps: U.S. patent application No.20020166341 teaches the use of a fast diffusing gas (e.g., helium or hydrogen) to displace residual gas present in voids defined by quartz sand patent application No. epo 693461A1 discloses a different method for producing quartz crucibles free of fine bubble aggregates and of high purity by controlling the amount of copper, chromium and nickel in the SiO 2 feed to 0.5 ppb or less, iron to 120ppb or less, and sodium to 20ppb or less.
The prior technical method comprises the following steps: when the quartz crucible vacuum arc method is used for preparing the synthetic quartz crucible, bubbles in the gap of the transparent layer of the quartz crucible cannot be completely pumped away, so that certain micro-bubbles still exist in the gap. The microbubbles are expanded and broken by heating in the crystal pulling process, and tiny quartz particles fall into the silicon liquid during the breaking, so that the purity of the monocrystalline silicon is reduced to a certain extent. The breakage of microbubbles on the inner surface of the quartz crucible also greatly causes the fluctuation of the liquid level to become large during the crystal pulling, thereby causing difficulty in the crystal pulling and easy breakage. And crystallization is easier to induce in the cracking place, and the purity of monocrystalline silicon is also affected by the falling of the crystallization part.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides the low-microbubble semiconductor-grade synthetic quartz crucible, the preparation method thereof and the monocrystalline silicon growth method.
In order to achieve the technical effects, the invention adopts the following technical scheme:
the invention aims at providing a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state.
As a preferable technical scheme of the invention, the pressure of the high-pressure air is 0.08-0.3 MPa, such as 0.08 MPa, 0.1MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa or 0.3MPa, but is not limited to the listed values, and is preferably 0.08-0.1 MPa.
As a preferable technical scheme of the invention, the mixed gas of the simple substance gas and the oxygen is introduced into the exhaust treatment and vacuumized, and the density of the simple substance gas is less than that of air.
Preferably, the volume fraction of the elementary gas in the mixed gas is 80-90%, and the volume fraction of the oxygen is 10-20%. The volume fraction of the elemental gas may be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or the like, and the volume fraction of the oxygen may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or the like, but the present invention is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned respective ranges are equally applicable.
Preferably, the elemental gas comprises any one or a combination of at least two of helium, argon or nitrogen. However, the present application is not limited to the above-mentioned gases, and other inert gases or simple substance gases having poor reactivity under the preparation conditions of the quartz crucible may be suitable for the present application.
In the envelope treatment, the arc striking power of the graphite electrode is 10 to 15 kW, such as 10kW, 11 kW, 12 kW, 13 kW, 14 kW or 15 kW, but the arc striking power is not limited to the recited values, and other non-recited values in the range of the recited values are equally applicable.
Preferably, in the envelope treatment, the mixed gas is kept in and evacuated.
In the preferred embodiment of the present invention, the power of the graphite electrode is 25 to 30 kW, such as 25 kW, 26 kW, 27 kW, 28 kW, 29 kW or 30 kW, etc., in the transparent layer melting, but the present invention is not limited to the listed values, and other non-listed values in the range of the values are equally applicable.
Preferably, in the transparent layer melting process, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out.
In a preferred embodiment of the present invention, the power of the graphite electrode is 16 to 20 kW, such as 16 kW, 17 kW, 18 kW, 19 kW, or 20 kW, in the bubble layer melting, but the present invention is not limited to the listed values, and other values not listed in the range of values are equally applicable.
Preferably, in the bubble layer melting process, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized.
As a preferred embodiment of the present invention, the cooling is nitrogen cooling.
The second object of the invention is to provide a semiconductor grade synthetic quartz crucible which is prepared by the preparation method of the low-microbubble semiconductor grade synthetic quartz crucible provided by the first object.
The third object of the present invention is to provide a semiconductor grade synthetic quartz crucible for use in a semiconductor grade single crystal silicon growing method.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The invention provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which adopts high-pressure air to support combustion, effectively solves the problem that the inner surface microbubbles cannot be ablated effectively at high temperature in the process of preparing a 32-inch synthetic crucible because of insufficient heat of a large-size quartz crucible, and reduces the manufacturing difficulty of synthesizing the large-size quartz crucible;
(2) The invention provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which adopts the mixed gas of simple substance gas and air for exhaust treatment, so that the air introduction in a quartz sand gap is greatly reduced, and the effect of removing bubbles in a transparent layer is remarkably improved;
(3) The invention provides a semiconductor grade monocrystalline silicon growth method, which is used for effectively improving the quality of monocrystalline silicon products by using the semiconductor grade synthetic quartz crucible prepared by the method.
Drawings
FIG. 1 is a schematic view of an apparatus for a method of manufacturing a low microbubble semiconductor grade synthetic quartz crucible according to an embodiment of the present invention;
In the figure: 1 is a high-purity graphite electrode; 2 is a high-pressure air combustion-supporting breather pipe; 3 is a mixed gas vent pipe; 4 is a graphite mold vacuumizing hole; 5 is a graphite mold; 6 is a quartz crucible bubble layer (natural high-purity quartz sand); 7 is a quartz crucible transparent layer (synthetic quartz sand); 8 is a transparent layer of a quartz crucible (natural high-purity quartz sand); 9 is an N2 breather pipe; 10 is a water cooled plate.
The present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
Detailed Description
The technical scheme of the application is further described through the specific embodiments.
The invention provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state.
Because the melting point of the synthetic sand on the inner surface of the synthetic crucible is low, compared with natural high-purity quartz sand, the synthetic sand is easier to melt. Therefore, the probability of vacuumizing and removing bubbles in the gap is greatly reduced, certain microbubbles are present on the inner surface, and a series of negative factors caused by the breakage of the microbubbles in the crystal pulling process can greatly influence the whole rod rate of the monocrystalline silicon. Although some micro bubbles are brought about by easier melting, the extremely high temperature can cause pressure change in the bubbles, so that the bubbles are broken and the effect of high-temperature ablation is achieved. However, due to the limitation of the graphite electrode discharge, the temperature brought by the electric arc is slightly lower, and complete ablation is not achieved. Therefore, the high-pressure air is loaded near the graphite electrode after the arc is started, so that the graphite electrode is fully supported, the current is improved to a certain extent, and the quality of the quartz crucible is obviously improved. Particularly for large-sized quartz crucibles, a large current is important.
In one specific embodiment of the invention, the high-pressure air can support combustion to improve the electric power by 5-20%.
In one embodiment of the invention, the quartz sand molding method can be as follows:
The first step: transferring the melting rotary die for 45-56 degrees, rotating at 65-70 rpm, pouring natural quartz sand (70-140 meshes) on the outer surface into the die, and then forming straight-wall natural high-purity quartz sand by using a forming rod;
A second part: the melting rotary die is transposed by 0 DEG, the rotating speed is 65-70 rpm, and a forming rod is used for scraping off natural high-purity quartz sand of a straight wall part to enable the quartz sand to fall into the bottom until the forming of the outer surface of the whole crucible is completed;
And a third step of: forming a straight wall by using part of the synthetic quartz sand by using a forming machine until the straight wall is formed;
Fourth step: and finally, manually forming the bottom and the R angle part, and remaining synthetic quartz sand until the final forming is finished.
In one specific embodiment of the invention, mixed gas consisting of simple substance gas and oxygen is introduced into the mold, so that air in the mold and air in a quartz sand gap are removed as much as possible, and the time can be 3-4 min.
In a specific embodiment of the invention, vacuum is pumped in the exhaust treatment process, and the vacuum pressure is 0 to-0.99 MPa.
For gaps on the inner surface of synthetic sand of a synthetic quartz crucible, a large amount of air is often present on the inner surface during the gaps after molding, so that micro bubbles in a transparent layer are extremely easy to generate. In the invention, the air in the quartz sand gap is replaced by introducing a proper mixed gas (simple substance gas and oxygen). Effectively preventing air or other gases from entering, thereby reducing the formation of bubbles. It can more evenly distribute and conduct heat, and is helpful for more even temperature distribution inside the quartz crucible. Such a uniform temperature distribution may reduce bubbles generated due to local overheating. Further, the density of the elemental gas is lower than that of air, so that the bubbles are less likely to remain in the quartz crucible. And can prevent the introduction of harmful gas or impurities and improve the pollution brought in the quartz crucible process. And combustion of a certain amount of oxygen is more conducive to reducing bubbles in the gap of the quartz crucible.
In one specific embodiment of the invention, in the cover treatment, the mixed gas is kept to be introduced, and the introducing speed of the mixed gas is 0.25-0.5 MPa/min.
In one specific embodiment of the invention, vacuum is maintained in the process of melting the transparent layer, and the vacuum pressure is 0 to-0.99 MPa.
In one embodiment of the present invention, the time for processing the cover may be 1-2 minutes.
In one specific embodiment of the invention, the mixed gas is kept to be introduced in the transparent layer melting process, and the introducing rate of the mixed gas is 0.25-0.5 MPa/min.
In one specific embodiment of the invention, vacuum is maintained in the process of melting the transparent layer, and the vacuum pressure is 0 to-0.99 MPa.
In one embodiment of the present invention, the time for melting the transparent layer may be 3 to 4 minutes.
In one embodiment of the invention, the time for melting the bubble layer may be 6-10 min.
In one specific embodiment of the invention, the graphite arc is closed before cooling, high-pressure air combustion supporting is stopped, nitrogen is introduced into the mold, the quartz crucible is rapidly cooled, and the nitrogen introduction time can be 2-3 min.
In one specific embodiment of the invention, after cooling is completed, the material is discharged from the furnace, and the demoulding and melting are completed.
According to the invention, the quartz crucible is rapidly cooled by using nitrogen, which is beneficial to shortening the production period and improving the production efficiency. Since semiconductor manufacturing typically involves multiple high temperature steps, rapid cooling can reduce the latency between each step, making the overall production process faster and more efficient. Second, rapid cooling helps to reduce thermal stresses. At high temperatures, the quartz crucible and the materials therein may be subjected to thermal stresses, resulting in deformation or cracking. By rapid cooling, the temperature gradient of the material can be rapidly reduced, and the generation of thermal stress can be reduced, thereby protecting the integrity of the quartz crucible and the semiconductor material. In addition, rapid cooling also helps to improve the quality of the crystals. In semiconductor manufacturing, the quality of the crystals is critical to the performance of the final product. By rapid cooling, the growth rate and structure of the crystal can be controlled, defects and impurities can be reduced, and thus a higher quality crystal can be obtained. Finally, rapid cooling also helps to save energy and reduce costs. By reducing the cooling time, the energy consumption can be reduced, and the use and maintenance cost of equipment can be reduced, so that the method has important significance for the economic benefit and sustainable development of semiconductor manufacturing enterprises.
In one embodiment of the present application, in the semiconductor grade single crystal silicon growing method, except for using the semiconductor grade synthetic quartz crucible provided by the present application, the other conditions can be appropriately adjusted according to the single crystal silicon growing method commonly used in the art, and are not further limited herein.
For a better illustration of the present invention, which is convenient for understanding the technical solution of the present invention, exemplary but non-limiting examples of the present invention are as follows:
Example 1
The embodiment provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
In the exhaust treatment, introducing mixed gas of helium (volume fraction 80%) and oxygen (volume fraction 20%) and vacuumizing, wherein the density of the simple substance gas is less than that of air;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state;
in the transparent layer melting process, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out;
in the process of bubble layer melting, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized;
closing the graphite arc before cooling, stopping high-pressure air combustion supporting, introducing nitrogen into the mold, and rapidly cooling the quartz crucible;
And after cooling, discharging from the furnace, demoulding and melting.
The conditions of each step in example 1 are shown in Table 1.
TABLE 1
Example 2
The embodiment provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
In the exhaust treatment, a mixed gas of monoatomic gas (volume fraction 90%) and oxygen (volume fraction 10%) is introduced and vacuumized, wherein the density of the elemental gas is less than that of air;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state;
in the transparent layer melting process, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out;
in the process of bubble layer melting, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized;
closing the graphite arc before cooling, stopping high-pressure air combustion supporting, introducing nitrogen into the mold, and rapidly cooling the quartz crucible;
And after cooling, discharging from the furnace, demoulding and melting.
The conditions of each step in example 2 are shown in Table 2.
TABLE 2
Example 3
The embodiment provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
in the exhaust treatment, introducing mixed gas of helium (volume fraction 85%) and oxygen (volume fraction 15%) and vacuumizing, wherein the density of the simple substance gas is less than that of air;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state;
in the transparent layer melting process, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out;
in the process of bubble layer melting, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized;
closing the graphite arc before cooling, stopping high-pressure air combustion supporting, introducing nitrogen into the mold, and rapidly cooling the quartz crucible;
And after cooling, discharging from the furnace, demoulding and melting.
The conditions of each step in example 3 are shown in Table 3.
TABLE 3 Table 3
Example 4
The embodiment provides a preparation method of a low-microbubble semiconductor-grade synthetic quartz crucible, which comprises the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
in the exhaust treatment, introducing mixed gas of helium (volume fraction 85%) and oxygen (volume fraction 15%) and vacuumizing, wherein the density of the simple substance gas is less than that of air;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state;
in the transparent layer melting process, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out;
in the process of bubble layer melting, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized;
closing the graphite arc before cooling, stopping high-pressure air combustion supporting, introducing nitrogen into the mold, and rapidly cooling the quartz crucible;
And after cooling, discharging from the furnace, demoulding and melting.
The conditions of each step in example 4 are shown in Table 4.
TABLE 4 Table 4
Example 5
In this example, the conditions were the same as in example 3 except that helium was replaced with argon.
Comparative example 1
The comparative example was conducted in the same manner as in example 3, except that the combustion was not conducted by high-pressure air.
Comparative example 2
The comparative example was conducted in the same manner as in example 3 except that helium (i.e., oxygen was not used) was used for the exhaust gas treatment.
Comparative example 3
The comparative example was conducted under the same conditions as in example 3, except that the exhaust gas treatment was conducted using a mixed gas of helium and nitrogen.
Comparative example 4
The comparative example was conducted under the same conditions as in example 3 except that the exhaust gas treatment was not conducted.
Comparative example 5
In this comparative example, the conditions were the same as in example 3 except that the cover treatment and the transparent layer melting were stopped from introducing the mixed gas.
Comparative example 6
In this comparative example, the conditions were the same as in example 3 except that no nitrogen gas was introduced during the cooling stage, i.e., natural cooling was performed.
Examples 1-5 and comparative examples 1-6 the method during the silica sand molding stage may be:
The first step: transferring the melting rotary die for 45-56 degrees, rotating at 65-70 rpm, pouring natural quartz sand (70-140 meshes) on the outer surface into the die, and then forming straight-wall natural high-purity quartz sand by using a forming rod;
A second part: the melting rotary die is transposed by 0 DEG, the rotating speed is 65-70 rpm, and a forming rod is used for scraping off natural high-purity quartz sand of a straight wall part to enable the quartz sand to fall into the bottom until the forming of the outer surface of the whole crucible is completed;
And a third step of: forming a straight wall by using part of the synthetic quartz sand by using a forming machine until the straight wall is formed;
Fourth step: and finally, manually forming the bottom and the R angle part, and remaining synthetic quartz sand until the final forming is finished.
The preparation methods provided in examples 1-5 and comparative examples 1-6 were used to prepare 32 inch synthetic quartz crucibles, the apparatus is shown in fig. 1, and the quality of the quartz crucible was effectively improved by using the above-described preparation method of the quartz crucible.
The prepared quartz crucible was tested for performance, and the results are shown in table 5.
The test method of straight-wall microbubbles and R-angle microbubbles comprises the following steps: the microbubbles in the quartz crucible were observed using an optical microscope or an electron microscope. The form, size and distribution of the microbubbles can be clearly seen by adjusting the magnification and focal length of the microscope. During the observation, attention is paid to the irradiation angle and intensity of the light to ensure that the microbubbles can be clearly observed. Then, the image capturing and analysis are performed on the microbubbles in the quartz crucible in combination with a high resolution camera and image processing software. By setting appropriate thresholds and algorithms, the software can automatically identify and count microbubbles, while also measuring the size and distribution of microbubbles.
The maximum stress test method comprises the following steps: the use of a polarization stress meter to detect stress in quartz glass is a common and effective method. Firstly, a 1/4 wave plate of a polarization stress meter is placed in a view field, and the zero point of the polarization stress meter is adjusted to form a dark view field. After the measuring point is selected, the analyzer is rotated to observe the movement of the dark cross. With the dark area moving outward, blue-grey will appear on the concave side of the stripe and brown on the convex side. The analyzer was continued to be rotated until the blue gray appearing at the measurement site was just replaced with brown, and the stress value at that time was recorded. To find the point of maximum stress, the sample can be rotated about the axis, and once the blue-gray appears, the analyzer is continued to be rotated so that the blue-gray is replaced with brown. The rotation of the sample about the axis is continued until the sample no longer appears blue-grey. The stress value recorded at this time is the stress value of the maximum stress point.
TABLE 5
As can be seen from the test results of Table 5, the 32-inch synthetic quartz crucible prepared by the preparation method of the low-microbubble semiconductor-grade synthetic quartz crucible provided in examples 1-5 has fewer microbubbles at the straight wall and the R angle, has good strength, and can effectively avoid the influence of thermal expansion and cracking of the microbubbles on the quality of monocrystalline silicon in the crystal pulling process when being used for preparing monocrystalline silicon. The comparative example 1 was not subjected to high-pressure air combustion supporting, resulting in a significant increase in micro bubbles in the synthetic quartz crucible at the straight wall and the R angle. Comparative example 2 was subjected to the degassing treatment using helium alone, comparative example 3 was subjected to the degassing treatment using a mixture of helium and nitrogen, and without using oxygen, the quartz crucible was also significantly increased in microbubbles at the straight wall and the R angle. Comparative example 4 was not subjected to the exhaust treatment, and comparative example 5 was fed with the mixed gas only during the exhaust treatment, and stopped feeding during the envelope treatment and the transparent layer melting, and the microbubbles in the quartz crucible were also significantly increased at the straight wall and the R angle. Comparative example 6 was not cooled with nitrogen gas, and although the change of microbubbles at the straight wall and the R angle was not significant in the quartz crucible, the stress of the quartz crucible was lowered compared with example 5.
The applicant states that the detailed structural features of the present invention are described by the above embodiments, but the present invention is not limited to the above detailed structural features, i.e. it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope of the present invention and the scope of the disclosure.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.
In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.
Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.
Claims (10)
1. A method for preparing a low-microbubble semiconductor-grade synthetic quartz crucible, which is characterized by comprising the following steps:
Sequentially carrying out exhaust treatment, envelope treatment, transparent layer melting, bubble layer melting and cooling on the quartz crucible after quartz sand molding;
in the envelope treatment, high-pressure air is introduced to support combustion after the graphite electrode is in an arc state.
2. The method according to claim 1, wherein the pressure of the high-pressure air is 0.08-0.3 mpa, preferably 0.08-0.1 mpa.
3. The preparation method according to claim 1, wherein the exhaust treatment is performed by introducing a mixed gas of an elemental gas and oxygen gas, and evacuating, the elemental gas having a density less than that of air;
Preferably, the volume fraction of the simple substance gas in the mixed gas is 80-90%, and the volume fraction of the oxygen is 10-20%;
Preferably, the elemental gas comprises any one or a combination of at least two of helium, argon or nitrogen.
4. The method according to claim 3, wherein the rate of introducing the mixed gas is 0.25 to 0.5 MPa/min.
5. The method according to claim 1, wherein in the envelope treatment, the arc starting power of the graphite electrode is 10 to 15 kW;
preferably, in the envelope treatment, the mixed gas is kept in and evacuated.
6. The method according to claim 1, wherein the power of the graphite electrode in the transparent layer melting is 25-30 kW;
preferably, in the transparent layer melting, the mixed gas is kept to be introduced, high-pressure air is used for supporting combustion and vacuumizing is carried out.
7. The method according to claim 1, wherein the power of the graphite electrode in the bubble layer melting is 16-20 kW;
preferably, in the process of melting the bubble layer, high-pressure air is kept for supporting combustion, and the mixed gas is stopped from being introduced and vacuumized.
8. The method of claim 1, wherein the cooling is nitrogen cooling.
9. A semiconductor grade synthetic quartz crucible, characterized in that it is prepared by the method for preparing a low microbubble semiconductor grade synthetic quartz crucible according to any of claims 1-8.
10. A semiconductor-grade single crystal silicon growing method, characterized in that the semiconductor-grade single crystal silicon growing method uses the semiconductor-grade synthetic quartz crucible according to claim 9.
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