CN214937960U - Quartz glass crucible - Google Patents
Quartz glass crucible Download PDFInfo
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- CN214937960U CN214937960U CN202022692088.1U CN202022692088U CN214937960U CN 214937960 U CN214937960 U CN 214937960U CN 202022692088 U CN202022692088 U CN 202022692088U CN 214937960 U CN214937960 U CN 214937960U
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Abstract
Provided is a quartz glass crucible which can improve the reliability when lifted by vacuum suction. The quartz glass crucible (1) has a cylindrical side wall portion (10 a), a bottom portion (10 b), and a corner portion (10 c) provided between the side wall portion (10 a) and the bottom portion (10 b), and the angle of inclination of the opening surface at the upper end of the periphery of the side wall portion (10 a) with respect to the horizontal plane is 0.01 DEG to 5 deg.
Description
Technical Field
The present invention relates to a quartz glass crucible, and more particularly to a shape of a peripheral upper end portion of a quartz glass crucible for pulling a silicon single crystal.
Background
A quartz glass crucible is used for producing a silicon single crystal by the CZ method. In the CZ method, a silicon raw material is heated and melted in a quartz glass crucible, seeds are immersed in the silicon melt, and the seeds are gradually pulled up while the crucible is rotated to grow a single crystal. According to the CZ method, a high-quality silicon single crystal for a semiconductor element free from dislocations and defects can be produced at a high yield.
The silica glass crucible for pulling a silicon single crystal is manufactured by a so-called rotary mold method. The rotary mold method is a method in which quartz powder is put into a rotating carbon mold and the quartz powder having an appropriate thickness is deposited on the inner surface of the mold conforming to the outer surface shape of the crucible. Since the quartz powder is attached to the inner surface of the crucible by a centrifugal force and the shape of the crucible is maintained, the quartz powder is melted by an arc to manufacture a quartz glass crucible.
After the quartz glass crucible thus produced is trimmed, the crucible product is shipped through a washing step and an inspection step. As for the trimming of the crucible, for example, patent document 1 describes a trimming device for stably and accurately cutting the peripheral edge of a glass crucible. Further, patent document 2 describes the following method: the eccentric amount and inclination amount of the crucible were determined from the distance L1 to the upper end side and the distance L2 to the lower end side of the crucible, the crucible was tilted so that the posture was vertical, and the posture of the crucible was controlled so that the difference between the distances L1 and L2 became zero. Further, patent documents 3 and 4 describe a method of chamfering the upper end of the peripheral edge of the silica glass crucible.
Since the silica glass crucible for pulling a silicon single crystal is large and heavy, a vacuum adsorption apparatus is often used for lifting the crucible (see, for example, patent document 5). During the raising of the crucible by the vacuum suction apparatus, the crucible is raised together with the lid after the crucible is sucked by vacuum-pumping the crucible through the suction hole through which the lid is passed, with the lid covering the upper surface of the crucible. According to this method, the crucible can be lifted safely without damaging the outer surface of the crucible. Such a crucible lifting step is performed, for example, when a crucible filled with polycrystalline silicon raw material is set in a single crystal pulling apparatus or a new crucible stored in a corrugated box is taken out.
Patent document 1: japanese patent laid-open No. 2001 and 226134.
Patent document 2: japanese patent laid-open No. 2001-348239.
Patent document 3: international publication No. 2017/110762, single file.
Patent document 4: japanese Kokai publication Hei-3-63581.
Patent document 5: japanese patent laid-open publication No. 2009-269769.
However, when the state of the edge cutting is poor, there is a problem that a sufficient degree of vacuum cannot be achieved in the crucible when the crucible is lifted by vacuum suction. If the degree of vacuum in the crucible cannot be sufficiently increased, the crucible may fall and be damaged during the lifting process.
SUMMERY OF THE UTILITY MODEL
Therefore, an object of the present invention is to provide a quartz glass crucible capable of improving reliability when lifted by vacuum adsorption.
In order to solve the above problem, the quartz glass crucible of the present invention has a cylindrical side wall portion, a bottom portion, and a corner portion provided between the side wall portion and the bottom portion, and an inclination angle of an opening surface of a peripheral upper end of the side wall portion with respect to a horizontal plane is 0.01 ° to 5 °.
When the crucible having a largely inclined opening surface is vacuum-sucked, the crucible is lifted up with the central axis of the crucible inclined with respect to the vertical axis. When the crucible in such an inclined state is set in the single crystal pulling apparatus, the yield of single crystals and the quality of crystals are reduced by eccentric rotation of the crucible. However, if the angle of the opening surface at the upper end of the peripheral edge is 5 ° or less, the central axis of the crucible can be lifted without being inclined by vacuum suction when the crucible is lifted. Therefore, when the crucible is installed in the pulling furnace of the single crystal pulling apparatus, the crucible can be installed in the carbon susceptor in the correct orientation, and the eccentric rotation of the crucible in the pulling step can be prevented.
Further, the quartz glass crucible of the present invention is characterized in that the flatness of the peripheral upper end surface of the side wall portion is 0.01mm or more and 5mm or less. According to the utility model discloses, can improve the inside vacuum of crucible when lifting up the crucible with vacuum adsorption device, can improve the reliability when lifting up the crucible.
Further, the quartz glass crucible of the present invention is characterized in that the number of cracks at the upper end of the peripheral edge is 20 or less, and the size of the cracks is 0.01mm to 10 mm. If a large number of large cracks are formed at the upper end of the peripheral edge, the gap between the cracks does not increase the vacuum degree during vacuum suction, making it difficult to lift the crucible. However, if the number and size of the cracks at the upper end of the peripheral edge are within the above ranges, the degree of vacuum in the crucible can be increased when the crucible is lifted by the vacuum suction apparatus, and the crucible can be reliably vacuum-sucked.
< bubble content in transparent layer >
Preferably, the quartz glass crucible of the present invention comprises a transparent layer and a bubble layer, wherein the transparent layer is made of silica glass containing no bubbles and constitutes an inner surface of the crucible, the bubble layer is made of silica glass containing a plurality of bubbles and is provided outside the transparent layer, and a bubble content of the transparent layer is 0.1vol% or less. This can prevent a decrease in the yield of single crystals due to bubbles.
In the utility model, the transparent layer is not required to be arranged on the whole of the crucible, and can be only arranged on the bottom and the corner part, and also can be only arranged on the bottom. The quartz glass crucible of the present invention may have a 3-layer structure including a transparent layer on the outer side of the bubble layer, or may have a 4-layer structure including a bubble layer on the outer side of the transparent layer, and various layer structures may be employed. Further, a layer made of another material may be provided between the transparent layer and the bubble layer.
In the present invention, it is preferable that the side wall portion has a side wall upper portion which is a region extending downward from the upper end of the peripheral edge and having a height of 150mm to 200mm, and a side wall lower portion which is a region located below the side wall upper portion, the side wall lower portion has the transparent layer and the bubble layer, and the side wall upper portion has the bubble layer and does not have the transparent layer. Since the region having a height of 150mm to 200mm extending downward from the upper end of the peripheral edge does not contact the silicon melt for a long time, even if the region contains a slight amount of bubbles, the region has no problem, and further, the effect of suppressing the vibration of the liquid surface of the silicon melt can be exhibited.
In the present invention, it is preferable that the bubble content in the vicinity of the crucible inner surface in the upper portion of the side wall is larger than 0.1% and not more than 3%. Thus, the bubble content in the upper portion of the side wall may be low or high.
In the present invention, the number density of the bubbles in the bubble layer is preferably 20/cm3Above 300/cm3The following. The average diameter of the cells in the cell layer is preferably 20 μm to 100 μm.
In the present invention, the bubble content of the transparent layer is preferably 0.05vol% or less. However, as described above, the bubble content of the transparent layer on the upper portion of the side wall of the crucible, which is not in contact with the silicon melt in the single crystal pulling step, may be 0.05vol% or more. Therefore, for example, the bubble content of the transparent layer at a position of 150mm to 200mm from the upper end of the peripheral edge may be 0.05 to 0.1 vol%. Alternatively, the bubble content in the region extending downward from the upper end of the peripheral edge of the crucible and having a height of 150mm to 200mm, that is, in the vicinity of the inner surface of the upper portion of the side wall of the crucible, may be larger than 0.1% and 3% or less.
Preferably, in the present invention, the bubble content of the transparent layer in the side wall portion (W portion) is higher than the bubble content of the transparent layer in the bottom portion (B portion) (W portion > B portion), and the bubble content of the transparent layer in the corner portion (C portion) is higher than the bubble content of the transparent layer in the bottom portion (B portion) (C portion > B portion).
Preferably, the transparent layer includes a synthetic transparent layer made of silica glass obtained by melting synthetic silica powder and a natural transparent layer made of silica glass obtained by melting natural silica powder, and the bubble content of the synthetic transparent layer is lower than the bubble content of the natural transparent layer.
The bubble content of the transparent layer in the bottom portion is preferably 4/5 or less of the bubble content of the transparent layer in the side wall portion.
< Infrared transmittance >
Preferably, the side wall portion (W portion) has a higher infrared transmittance than the bottom portion (B portion) (W portion > B portion), and the bottom portion (B portion) has a higher infrared transmittance than the corner portion (C portion) (B portion > C portion).
Preferably, the bottom portion has an infrared transmittance that decreases from the center of the bottom portion toward the corner portion.
Preferably, the side wall portion has an infrared transmittance that decreases from above to below the side wall portion.
< distribution of wall thickness >
Preferably, the distance from the center of the bottom to the maximum thickness position of the crucible in the direction from the center of the bottom to the upper end of the peripheral edge of the inner surface of the crucible is 0.35 to 0.65 in terms of the distance (total length) from the center of the bottom to the upper end of the peripheral edge.
Preferably, the corner portion has a position where the wall thickness is largest, and further, the bottom portion has a position where the wall thickness of the crucible is smallest.
The maximum wall thickness of the crucible is preferably 1.5 to 5% of the diameter of the crucible.
Preferably, the portion having the smallest infrared transmittance is within ± 30mm from the maximum thickness position in a direction from the center of the bottom of the inner surface of the crucible toward the upper end of the peripheral edge.
Preferably, the thickness of the bottom portion is thicker from the center of the bottom portion toward the corner portion.
< distribution of transparent layer >
Preferably, the distance from the center of the bottom to the maximum thickness position of the transparent layer is 0.35 to 0.65 in the distance from the center of the bottom to the upper end of the peripheral edge of the inner surface of the crucible in the direction from the center of the bottom to the upper end of the peripheral edge.
The transparent layer preferably has a thickness of 1mm or more of 90% or more of the entire thickness.
Preferably, the thickness of the transparent layer is largest at the corner.
Preferably, the rate of change in the thickness of the transparent layer is greatest at the corner.
The rate of change in the thickness of the transparent layer is preferably 9.8mm/cm or less.
< synthetic layer seed/natural layer distribution >
Preferably, the quartz glass crucible of the present invention has a synthetic layer made of silica glass formed by melting synthetic silica powder and a natural layer made of silica glass formed by melting natural silica powder, and the thickness of the synthetic layer is 0.5 times or less the thickness of the natural layer. Thus, impurity contamination of the silicon single crystal is prevented, and the heat retaining property and durability of the crucible can be ensured.
The quartz glass crucible of the present invention is preferably such that the thickness of the composite layer is 30% or less of the wall thickness of the crucible.
Preferably, in the present invention, the thickness of the composite layer of the side wall portion becomes thicker downward.
< crucible shape (external open) >)
Preferably, in the present invention, the side wall portion is open on the outside, and the height from the upper end of the periphery to the maximum outer diameter position of the crucible/the height of the crucible is 0.3 or less.
< roughness of internal surface >
Preferably, in the present invention, the inner surface roughness is smaller than the outer surface roughness.
< roughness of peripheral upper end face >
Preferably, in the present invention, the surface roughness of the peripheral upper end surface of the side wall portion is 0.01 μm or more and 500 μm or less.
< Properties of glass >
The OH group concentration on the inner surface of the crucible is preferably 250ppm or less. When the OH group concentration is high, the quartz glass contains a large amount of bubbles inside, and the viscosity at high temperature is low, so that the amount of erosion at the time of pulling up the silicon single crystal is large, and in an extreme case, peeling occurs, which causes a decrease in the quality of the single crystal silicon and a decrease in the single crystal yield. However, when the OH group concentration on the inner surface of the crucible is suppressed to 250ppm or less, the viscosity of the inner surface of the crucible can be increased, and the durability of the crucible and the single crystallization yield can be improved.
< crystallization technique >
Preferably, the quartz glass crucible of the present invention further comprises a crystallization accelerator-containing coating film formed on the inner surface and/or the outer surface of the crucible, wherein the thickness of the crystallization accelerator-containing coating film is 1mm or less. The crystallization accelerator-containing coating film may be formed on the entire crucible or may be formed on a part thereof. When the crystallization promoter is formed in a part of the crucible, the coating film containing the crystallization promoter may be formed on the entire surface ranging from the corner portion to the sidewall portion, may be formed only on the corner portion, or may be formed only on the sidewall portion. By using the crystallization accelerator, crystallization of the surface of the crucible can be promoted, the strength of the crucible can be improved, and a decrease in yield of single crystals due to peeling of crystal grains can be prevented.
Preferably, the crystallization promoter coated or doped on the inner surface and/or the outer surface of the crucible is a group 2 element, an alkali metal, an alkaline earth metal, or a group 13 element. By using these raw materials, crystallization of the surface of the quartz glass crucible can be promoted.
The quartz glass crucible of the present invention preferably has a semi-molten layer on the outermost side.
Effect of the utility model
According to the utility model discloses, can provide the quartz glass crucible that can improve the reliability when lifting up through vacuum adsorption.
Drawings
FIG. 1 is a view showing the structure of a silica glass crucible according to a preferred embodiment of the present invention, wherein (a) is a substantially perspective view and (b) is a substantially side sectional view.
FIG. 2 is a flowchart showing a process for producing a silica glass crucible.
FIGS. 3(a) and (b) are schematic views showing a method for producing a silica glass crucible.
FIG. 4 is a view for explaining trimming and edge treatment of a silica glass crucible, wherein (a) is a schematic view showing a trimming step and (b) is a schematic view showing a chamfering step.
Fig. 5(a) is a diagram for explaining flatness, and fig. 5(b) is a graph showing an example of height unevenness of the peripheral upper end surface.
FIG. 6 is a view for explaining the inclination angle of the opening face at the upper end of the peripheral edge of the silica glass crucible.
Detailed Description
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a view showing the structure of a silica glass crucible according to an embodiment of the present invention, wherein (a) is a substantially perspective view and (b) is a substantially side sectional view.
As shown in fig. 1(a) and (b), the quartz glass crucible 1 is a silica glass container for holding a silicon melt, and has a cylindrical side wall portion 10a, a bottom portion 10b, and a corner portion 10c provided between the side wall portion 10a and the bottom portion 10b and having a curvature larger than that of the bottom portion 10 b. The bottom 10b is preferably a so-called round bottom which is gently curved, but may also be a so-called flat bottom. The boundary position between the side wall portion 10a and the corner portion 10c is a position where the side wall portion 10a starts to bend. The boundary position between the corner portion 10c and the bottom portion 10b is a position where the larger curvature of the corner portion 10c starts to change to the smaller curvature of the bottom portion 10 b.
The diameter (bore diameter) of the silica glass crucible 1 varies depending on the diameter of the silicon single crystal ingot to be pulled using the crucible, and is preferably 22 inches (about 560mm) or more, and particularly preferably 32 inches (about 800mm) or more. This is because such a large-diameter crucible is used for pulling a large silicon single crystal ingot having a diameter of 300mm or more, and it is necessary that the quality of the single crystal is not affected even when the crucible is used for a long time.
Although the crucible wall thickness varies slightly depending on the location, the wall thickness of the side wall portion 10a of a 22-inch or larger crucible is preferably 7mm or larger, and the wall thickness of the side wall portion 10a of a larger crucible of 32 inches or larger is preferably 10mm or larger. This enables a large amount of the silicon melt to be stably maintained at a high temperature.
The silica glass crucible 1 has a double-layer structure mainly, and includes a transparent layer 11 made of silica glass containing no bubbles, and a bubble layer 12 (opaque layer) made of silica glass containing a large number of bubbles and formed outside the transparent layer 11.
The transparent layer 11 is a layer constituting the inner surface 10i of the crucible wall which is in contact with the silicon melt, and is provided to prevent a decrease in the yield of single crystals due to bubbles in the silica glass. This is because, when bubbles are present in the vicinity of the inner surface of the crucible, the bubbles cannot be trapped in the silica glass due to the melting loss of the inner surface 10i of the crucible, and there is a possibility that fragments of the crucible (silica pieces) are peeled off when the bubbles in the silica glass are broken due to thermal expansion in the crystal pulling step. When the crucible fragments released into the molten liquid are carried to the growth interface of the single crystal by the convection of the molten liquid and are collected into the single crystal, they cause dislocation of the single crystal. Further, when bubbles released into the melt float up to reach the solid-liquid interface and are collected into the single crystal, they cause generation of pinholes in the silicon single crystal.
The transparent layer 11 "does not contain bubbles" means that the bubble content and the bubble size are such that the single crystallization rate is not decreased by bubbles. The bubble content is, for example, 0.1vol% or less, and the average diameter of the bubbles is, for example, 100 μm or less.
The thickness of the transparent layer 11 is preferably 0.5 to 10mm, and is set to a suitable thickness for the crucible portion so that the bubble layer 12 is not completely eliminated by the melting loss in the single crystal pulling step and is not exposed. The transparent layer 11 is preferably provided as the entire crucible from the side wall portion 10a to the bottom portion 10b of the crucible, as with the bubble layer 12, but the transparent layer 11 may be omitted at the upper end portion (peripheral portion) of the crucible which is not in contact with the silicon melt.
The bubble content and the diameter of the bubbles in the transparent layer 11 can be nondestructively measured by an optical detection means. The optical detection mechanism includes a light receiving device that receives transmitted light or reflected light of light emitted toward the crucible. The light emitting means for emitting light may be built in the light receiving device, or an external light emitting means may be used. Further, the optical detection mechanism is preferably used that is capable of rotationally operating along the inner surface of the crucible. As the irradiation light, in addition to visible light, ultraviolet light, and infrared light, X-rays, laser light, or the like can be used. The light receiving device can use a digital camera including an optical lens and an imaging element. The measurement result by the optical detection means is received by the image processing apparatus, and the diameter of the bubble and the bubble content per unit volume are calculated.
In order to detect bubbles existing at a certain depth from the surface of the crucible, the focal point of the optical lens may be scanned from the surface in the depth direction. Specifically, an image of the crucible inner surface was captured by a digital camera, the crucible inner surface was divided into reference areas S1 for each constant area, and the bubble occupied area S2 was obtained for each of the reference areas S1, and the area bubble content Ps was calculated as (S2/S1) × 100 (%).
In the calculation of the bubble content based on the volume ratio, the reference volume V1 is obtained from the depth of the captured image and the reference area S1. Further, the volume V2 of the bubbles was calculated from the diameters of the bubbles, taking the bubbles as spherical. Then, from V1 and V2, the volume bubble content Pv was calculated as (V2/V1) × 100 (vol%). In the present invention, the volume bubble content Pv is defined as "bubble content". The added average value obtained from the diameters of the bubbles calculated by regarding the bubbles as spherical is defined as "average diameter of the bubbles".
The reference volume was 5mm × 5mm × depth (depth) 0.45mm, and the diameter of the smallest bubble measured was 5 μm (disregarding that the diameter was less than 5 μm). Thus, the measurement device may have an analytical ability to measure bubbles having a diameter of 5 μm. Further, the focal length of the optical lens was shifted in the depth direction of the reference volume V1, and the bubble contained in the reference volume was captured to measure the diameter of the bubble.
< air bubble layer >
The bubble layer 12 is a layer constituting the outer surface 10o of the crucible, and is provided in order to improve the heat retaining property of the silicon melt in the crucible and to disperse the radiant heat from the heater surrounding the crucible in the single crystal pulling apparatus to heat the silicon melt in the crucible as uniformly as possible. Therefore, the bubble layer 12 is provided on the entire crucible from the side wall 10a to the bottom 10b of the crucible. The thickness of the bubble layer 12 is substantially equal to the value obtained by subtracting the thickness of the transparent layer 11 from the thickness of the crucible wall, and differs depending on the crucible location. The bubble content of the bubble layer 12 can be determined by, for example, measuring the specific gravity of an opaque silica glass piece cut out from a crucible (archimedes' method).
The bubble content of the bubble layer 12 is higher than that of the transparent layer 11, and is preferably greater than 0.1vol% and not more than 5vol%, and more preferably not less than 1vol% and not more than 4 vol%. This is because the bubble layer 12 cannot function as the bubble layer 12 if the bubble content of the bubble layer 12 is 0.1vol% or less, and the heat retaining property is insufficient. Further, when the bubble content of the bubble layer 12 exceeds 5vol%, the crucible may be largely deformed by expansion of the bubbles, and the yield of the single crystal may be lowered, and the heat conductivity may be insufficient. In particular, if the bubble content of the bubble layer 12 is 1 to 4%, the balance between the heat retaining property and the heat transfer property is good. The large number of bubbles contained in the bubble layer 12 can be recognized by visual observation. The bubble content is a value measured in a room temperature environment of the crucible before use.
< semi-molten layer >
A semi-molten layer may be formed on the outermost side of the crucible. The semi-molten layer is formed on the outer surface 10o of the quartz glass crucible 1 by cooling a part of silica powder, which is a raw material of the crucible, in an incompletely molten state (semi-molten state). The semi-molten layer has a surface with rich undulations, and is greatly scattered and reflected by light incident from the outer surface side of the crucible, and therefore affects the infrared transmittance of the crucible. The semi-molten layer is a layer formed during the production of the crucible, and is not a layer necessary for pulling the silicon single crystal, but there is no positive reason for removing the semi-molten layer, and therefore the crucible product is provided in a state in which the semi-molten layer is present. The thickness of the semi-melting layer is 0.05-2.0 mm, preferably 0.1-0.9 mm. The semi-molten layer is formed thinner as the temperature gradient near the outer surface of the crucible is more rapid and thicker as the temperature gradient is more gradual during crucible production. The thicker the semi-molten layer is, the larger the surface roughness becomes, and the quartz powder is easily detached. Further, since the temperature gradient near the outer surface of the crucible during crucible production differs depending on the location of the crucible, the thickness of the semi-molten layer also differs depending on the location of the crucible.
Whether or not a semi-molten layer is formed on the outer surface of the crucible can be determined by determining whether or not a halo pattern in which a diffraction image unique to amorphous is blurred and a peak indicating crystallinity are mixed when the outer surface of the crucible is measured by an X-ray diffraction method. For example, when the object to be measured is a crystal layer, a peak indicating crystallinity is detected, but a halo pattern in which a diffraction image is blurred is not detected. On the other hand, when the measurement target is an amorphous layer (amorphous layer), a halo pattern in which a diffraction image is blurred is detected, and a peak indicating crystallinity is not detected. When the semi-molten layer formed on the outer surface of the crucible is removed, the surface of the glass is exposed, and therefore, the peak cannot be detected by the X-ray diffraction method. In this way, the semi-molten layer can be referred to as a layer in which a halo pattern of a blurred diffraction image and a peak indicating crystallinity are mixed when measured by an X-ray diffraction method. Further, it can be said that the crystalline layer is a layer in which a peak is detected by X-ray diffraction, and the amorphous layer is a layer in which a halo pattern in which a diffraction image is blurred is detected.
In order to prevent contamination of the silicon melt, the silica glass constituting the transparent layer 11 is desirably high in purity. Therefore, the quartz glass crucible 1 of the present embodiment is preferably composed of a double layer of an inner synthetic silica glass layer formed from synthetic silica powder (hereinafter referred to as "synthetic layer") and an outer natural silica glass layer formed from natural silica powder (hereinafter referred to as "natural layer"). The synthetic silica powder can pass through silicon tetrachloride (SiCl)4) Gas phase oxidation (dry synthesis method), hydrolysis of silicon alkoxide (sol-seed-gel method). The natural silica powder is produced by pulverizing a natural mineral containing α -quartz as a main component into particles.
The two-layer structure of the synthetic layer and the natural layer can be manufactured by stacking natural silica powder along the inner surface of the crucible-manufacturing mold, stacking synthetic silica powder thereon, and melting these silica powders by joule heat based on arc discharge. In the initial stage of the arc melting step, bubbles are removed by strongly evacuating the outside of the silica powder deposition layer, thereby forming the transparent layer 11. Thereafter, the bubble layer 12 is formed on the outside of the transparent layer 11 by stopping or weakening the evacuation. Therefore, the boundary surface between the synthetic layer and the natural layer does not necessarily coincide with the boundary surface between the transparent layer 11 and the bubble layer 12, but the synthetic layer preferably has a thickness such that the synthetic layer does not completely disappear due to the melting loss of the inner surface 10i of the crucible in the crystal pulling step, as in the transparent layer 11.
< bubble content of transparent layer >
The bubble content of the transparent layer 11 is preferably 0.05vol% or less. The bubble content of the transparent layer 11 of the side wall portion 10a is preferably higher than the bubble content of the transparent layer 11 of the bottom portion 10 b. The bubble content of the transparent layer 11 at the corner portion 10c is preferably higher than the bubble content of the transparent layer 11 at the bottom portion 10 b. That is, the bubble content of the transparent layer 11 is preferably such that the side wall 10a > the bottom 10b and the corner 10c > the bottom 10b, and particularly preferably such that the corner 10c > the side wall 10a > the bottom 10 b.
When the transparent layer 11 is composed of a synthetic layer and a natural layer, the bubble content of the synthetic layer (synthetic transparent layer) in the transparent layer 11 is preferably lower than the bubble content of the natural layer (natural transparent layer) in the transparent layer 11 (bubble content of synthetic transparent layer < bubble content of natural transparent layer).
The bubble content of the transparent layer 11 in the side wall portion 10a at the initial liquid level position having a height of 150mm to 200mm extending downward from the upper end of the peripheral edge of the crucible may be 0.1vol% or less, or 0.1vol% or more. When the bubble content of the transparent layer 11 in the side wall portion 10a at the initial liquid surface position is 0.1vol% or less, the bubble content is preferably 0.01 to 0.1vol%, and particularly preferably 0.05 to 0.1 vol%. When the bubble content of the transparent layer 11 in the side wall portion 10a at the initial liquid level position is 0.1vol% or more, the bubble content in the vicinity of the inner surface of the crucible is preferably 0.1 to 3vol%, and preferably 0.1 to 0.5 vol%. By thus slightly increasing the bubble content at the initial liquid surface position in the vicinity of the inner surface of the crucible, the liquid surface vibration of the silicon melt can be suppressed.
The bubble content of the transparent layer 11 of the side wall portion 10a may not increase from the lower side to the upper side. The bubble content of the transparent layer 11 in the bottom portion 10b is preferably 4/5 or less of the bubble content of the transparent layer 11 in the side wall portion 10 a.
The region of the side wall 10a of the crucible, which is 200mm below the upper end of the peripheral edge, is defined as the upper side wall 10a1Will be larger than the upper part 10a of the side wall1The lower region is a sidewall lower portion 10a2In this case, only the sidewall lower portion 10a of the sidewall portion 10a may be provided2The transparent layer 11 is formed on the inner surface 10i side, and the upper portion 10a of the side wall is omitted1The transparent layer 11 on the inner surface 10i side. In this case, the upper side wall portion 10a1The bubble layer 12 is formed on the inner surface 10i side. That is, the upper side wall portion 10a may be formed1The bubble content in the vicinity of the inner surface 10i is set to 0.1vol% or less, and the sidewall upper portion 10a is set to be a wall portion1The bubble content in the vicinity of the inner surface 10i is larger than 0.1vol% (preferably 0.5 to 3 vol%).
The transparent layer 11 may have a two-layer structure in which the bubble content is different between the outermost layer and the other portions, or a sealing layer having a slightly higher bubble content may be provided on the outermost layer of the transparent layer 11. The thickness of the sealing layer is preferably 0.1mm to 2.0mm, and the bubble content of the sealing layer is preferably 0.1vol% to 5.0 vol%. The presence of such a sealing layer can suppress bumping of the silicon melt during melting of the silicon raw material. Further, since the sealing layer is melted and lost at the start of the single crystal pulling step, the yield of the single crystal can be prevented from being lowered due to the bubbles.
< bubble content of bubble layer >
The number density of bubbles in the bubble layer 12 is preferably 20 to 300/cm3More preferably 30 to 200 pieces/cm3. The average diameter of the bubbles in the bubble layer 12 is preferably 20 to 100 μm, and more preferably 30 to 100 μm. In particular, the bubble number density (number/cm) of the bubble layer 123) Preferably, the bottom portion 10b is lower than the side wall portion 10a (side wall portion 10a > bottom portion 10 b). This is because bubbles in the side wall portion 10a contribute to suppression of liquid surface vibration, but bubbles in the bottom portion 10b cause pinholes in the silicon single crystal and are desirably eliminated as much as possible.
< Infrared transmittance (IR) >
The crucible preferably has an infrared transmittance of 40 to 80%, particularly preferably 30 to 60%. The infrared transmittance of the side wall 10a and the bottom 10b of the crucible is preferably higher than that of the corner 10c (side wall 10a > corner 10c, bottom 10b > corner 10c), and the order of side wall 10a > bottom 10b > corner 10c is particularly preferred.
Preferably, the position where the thickness of the crucible is maximum is located at the corner 10c, and the position where the infrared transmittance is minimum is within ± 30mm from the position where the thickness of the crucible is maximum, in the direction from the center of the bottom 10b of the inner surface 10i of the crucible toward the upper end of the peripheral edge. The infrared transmittance of the side wall portion 10a is preferably decreased from the top to the bottom. The infrared transmittance of the bottom portion 10b is preferably smaller from the bottom center toward the corner portion 10 c. Since the quartz glass crucible 1 has such an infrared transmittance distribution, it is possible to pull a silicon single crystal having a low oxygen concentration by suppressing the amount of oxygen supplied from the crucible to the silicon melt.
Further, the absolute value of the rate of change in the infrared transmittance in the height direction of the wall surface of the crucible from the bottom center toward the peripheral upper end of the crucible is preferably 3%/cm or less. By making the change in the infrared transmittance gradual from the bottom to the side wall of the crucible, the unevenness of the temperature distribution of the inner surface 10i of the quartz glass crucible can be suppressed, and the sharp change of the oxygen concentration distribution in the longitudinal direction (crystal growth direction) of the silicon single crystal can be suppressed.
< distribution of wall thickness >
In the distance along the direction from the center of the bottom portion 10b of the inner surface 10i of the crucible to the upper end of the peripheral edge, the distance from the center of the bottom portion 10b to the position of maximum wall thickness/the distance from the center of the bottom portion 10b to the upper end of the peripheral edge (total length) is preferably 0.35 to 0.65. The absolute value of the rate of change in the wall thickness of the crucible is preferably 5.0mm/cm or less.
Preferably, there is a maximum wall thickness at the corner 10c of the crucible and a minimum wall thickness at the bottom 10b of the crucible. The maximum wall thickness of the crucible is preferably 1.5 to 5% of the maximum diameter of the crucible.
The portion where the infrared transmittance is smallest in the direction from the center of the bottom 10b of the inner surface 10i of the crucible toward the upper end of the peripheral edge is preferably within ± 30mm from the position where the wall thickness of the crucible is largest.
The wall thickness of the bottom 10b of the crucible is preferably thicker from the center of the bottom toward the corner 10 c. The wall thickness of the side wall 10a of the crucible is preferably increased from the top to the bottom.
< distribution of transparent layer >
In the distance along the direction from the center of the bottom 10b of the inner surface 10i of the crucible toward the upper end of the peripheral edge, the distance from the center of the bottom to the position where the thickness of the transparent layer 11 is the largest/the distance from the center of the bottom to the upper end of the peripheral edge (total length) is preferably 0.35 to 0.65. The absolute value of the rate of change in the thickness of the transparent layer 11 of the crucible is preferably 11.1mm/cm or less.
The thickness of the transparent layer 11 of the bottom portion 10b is preferably thicker from the center of the bottom portion toward the corner portion 10 c.
The region of the transparent layer 11 having a thickness of 1mm or more preferably accounts for 90% or more of the entire region where the transparent layer 11 is formed. The thickness of the transparent layer 11 is preferably the thickest at the corner 10 c. Further, the rate of change in the thickness of the transparent layer 11 is preferably greatest at the corner portion 10 c. The thickness of the transparent layer 11 at the corner 10c is preferably 10 times or more the thickness of the transparent layer 11 at the bottom 10 b.
< synthetic layer seed/natural layer distribution >
In the distance from the center of the bottom 10b of the inner surface 10i of the crucible toward the upper end of the peripheral edge, the distance from the center of the bottom 10b to the position where the thickness of the composite layer is the largest/the distance from the center of the bottom to the upper end of the peripheral edge (total length) is preferably 0.35 to 0.65. The thickness of the composite layer is preferably 0.5mm to 5.0mm, and the absolute value of the rate of change in the thickness of the composite layer is preferably 4.0mm or less.
The thickness of the inner synthetic layer is preferably 30% or less of the wall thickness of the crucible, and the thickness of the outer natural layer is preferably 0.5 times or less. Further, the composite layer of the side wall portion 10a preferably becomes thicker from the upper side to the lower side.
< crucible shape (external open) >)
The side wall 10a may be open to the outside, and the height from the upper end of the peripheral edge to the maximum outer diameter position of the crucible/the crucible height is preferably 0.3 or less. The outer diameter of the sidewall portion 10a in the vicinity of the upper end may be larger than the outer diameter of the sidewall portion 10a in the vicinity of the lower end.
Regarding the roundness of the crucible, when Sx represents the roundness of the inner surface 10i of the side wall portion 10a of the crucible, Sy represents the roundness of the outer surface 10o, and M represents the maximum wall thickness of the side wall portion 10a at the same measurement height as the roundness, both the roundness Sx and Sy are preferably 0.4 or less (Sx/M. ltoreq.0.4, Sy/M. ltoreq.0.4). This can suppress the liquid surface vibration caused by the eccentric rotation of the crucible.
< roughness of internal surface >
The surface roughness (arithmetic average roughness Ra) of the outer surface 10o and the inner surface 10i of the crucible is preferably 1mm or less, and the inner surface roughness of the crucible is preferably smaller than the outer surface roughness (inner surface roughness < outer surface roughness). When the arithmetic mean roughness of the outer surface of the crucible is larger than 1mm, the unevenness of the outer surface is sharp, and the base point of cracking or chipping due to the difference in level of the unevenness of the outer surface increases. The outer surface 10o of the crucible is easily subjected to external force during transportation or the like, and is easily cracked or broken by the external force. However, if the surface roughness (Ra) of the outer surface of the crucible is 1mm or less, the occurrence of cracks and chipping due to the level difference of the irregularities of the outer surface can be suppressed.
< roughness of peripheral upper end face >
The surface roughness (arithmetic mean roughness Ra) of the upper end surface of the peripheral edge of the crucible is preferably 0.01 μm to 500 μm.
< Properties of glass >
The OH group concentration on the inner surface of the crucible is preferably 250ppm or less. When the OH group concentration is high, the quartz glass contains a large amount of bubbles inside, and the viscosity at high temperature is low, so that the amount of erosion at the time of pulling up the silicon single crystal is large, and in an extreme case, peeling occurs, which causes a decrease in the quality of the single crystal silicon and a decrease in the single crystal yield. However, when the OH group concentration on the inner surface of the crucible is suppressed to 250ppm or less, the viscosity of the inner surface of the crucible can be increased, and the durability of the crucible and the single crystallization yield can be improved.
< crystallization technique >
The quartz glass crucible 1 of the present embodiment may be formed with a coating film containing a crystallization accelerator on the inner surface 10i and/or the outer surface 10o thereof, or may be formed by doping a crystallization accelerator into silica glass in the vicinity of the inner surface and/or the vicinity of the outer surface. The crystallization accelerator is preferably a group 2 element, an alkali metal, an alkaline earth metal, or a group 13 element, and particularly preferably barium. Barium has a smaller segregation coefficient than silicon, and has the advantage that the crystallization rate and crystallization are not reduced, and the barium is more easily grown in an oriented state than other elements. Further, since barium is stable at room temperature and easy to handle, and the radius of the atomic nucleus is about the same as that of silica glass, there is an advantage that a concentrated layer of barium is easily formed at the interface between the glass layer and the crystal layer. In the case of coating the surface of the crucible with the crystallization accelerator, the thickness of the crystallization accelerator coating film is preferably 1mm or less.
The band-shaped region having a constant width from the upper end of the peripheral edge of the crucible to the lower side is preferably a region not filled with the crystallization accelerator. This is because, when the upper end portion of the peripheral edge is coated or doped with a crystallization promoter, cracks are likely to occur from the crystallization region at the upper end portion of the peripheral edge, and particles of crystals that generate dust from the cracks may be mixed into the silicon melt in the crucible, thereby reducing the yield of silicon single crystals. However, when the uncoated region of the crystallization accelerator is provided at the upper end of the peripheral edge, the occurrence of particles can be prevented. In this way, the filling range of the crystallization accelerator may be the entire crucible or may be a part thereof. In the case of a part of the crucible, the crucible may be filled in a wide range from the corner portion 10c to the side wall portion 10a, and only the corner portion 10c may be used, or only the side wall portion may be used.
< Others >
Preferably, in the silica glass crucible 1, the internal residual stress of the inner surface side surface portion and the outer surface side surface portion of the crucible wall is compressive stress, and the internal residual stress of the central portion in the wall thickness direction between the inner surface side surface portion and the outer surface side surface portion is tensile stress. In this case, the thickness of the inner surface side surface portion and the outer surface side surface portion is preferably 1mm or more, and particularly preferably 3mm or more. According to this embodiment, the strength of the inner surface 10i and the outer surface 10o of the crucible is increased to prevent cracking and breaking of the crucible.
The carbon concentration in the surface layer region from the inner surface 10i of the crucible to a depth of 1mm is preferably 10ppm or less. By eliminating the cause of the generation of bubbles (gas supply source) from the crystallization region on the inner surface 10i side of the crucible, the probability of the separation of the crystal layer can be further reduced.
In the production of a silica glass crucible, silica powder having as high purity as possible, such as synthetic silica powder, is used on the inner surface 10i side of the crucible, and silica powder having low purity and low cost is often used on the outer surface 10o side of the crucible, because cost is more important than purity. In such a crucible having a two-layer structure in which the layer constituting the inner surface 10i side and the layer constituting the outer surface 10o side have different properties, the ratio η i/η o of the viscosity η o of the layer on the outer surface 10o side to the viscosity η i of the layer on the inner surface 10i side is preferably in the range of 0.5 to 10. Here, the two-layer structure refers to any of the transparent layer 11 and the bubble layer 12, or the synthetic layer and the natural layer (different silica glass layers), or two natural layers having different properties. The above-mentioned viscosity is 1450 ℃. When the viscosity ratio of the glass is in the range of 0.5 to 10, even when the surface layer portion of the crucible is crystallized and contracted, the contraction stress is relaxed to suppress the deformation of the crucible.
FIG. 2 is a flowchart showing a process for producing a silica glass crucible. Further, FIGS. 3(a) and (b) are schematic views showing a method for producing a silica glass crucible.
As shown in fig. 2 and fig. 3(a) and (b), the silica glass crucible 1 of the present embodiment can be manufactured by a so-called rotary mold method. In the rotary mold method, a carbon mold 20 having a cavity matching the outer diameter of the crucible is prepared, and a silica powder deposit layer 15 is formed in the rotating carbon mold 20 (step S101).
As shown in fig. 3(a), when the quartz glass crucible 1 has a double-layer structure of a synthetic layer and a natural layer, natural silica powder is supplied to the inner surface 20i of the carbon mold 20 to form a natural silica powder deposited layer 15a, and then synthetic silica powder is further supplied to form a synthetic silica powder deposited layer 15 b. At this time, the excessive silica powder is scraped off along the inner surface of the mold by using a scraper, and the natural silica powder deposit layer 15a and the synthetic silica powder deposit layer 15b are adjusted to have predetermined thicknesses suitable for respective portions of the crucible. The silica powder in the rotating carbon mold 20 remains at a predetermined position in a state of being attached to the inner surface of the mold by centrifugal force, and the shape thereof is maintained.
Next, as shown in fig. 3(b), the arc electrode 22 is provided in the cavity of the carbon mold 20, and the deposited layer 15 of silica powder is arc-melted (step S102). In the arc melting, the entire silica powder deposit layer 15 is heated to 1720 ℃ or higher to be melted. At this time, a thin sealing layer of silica glass is preferably formed on the inner surface of the silica powder accumulated layer 15. Then, the pressure is reduced from the carbon mold 20 side simultaneously with the heating, and the gas in the voids in the silica powder deposition layer 15 is sucked through the vent holes 21 provided in the carbon mold 20, whereby the transparent layer 11 (transparent silica glass layer) substantially free of bubbles is formed.
Thereafter, the suction of the deposition layer 15 with respect to the silica powder is reduced or stopped, and bubbles remain in the silica glass. Thereby, a bubble layer 12 (opaque silica glass layer) including a large number of minute bubbles is formed outside the transparent layer 11.
Then, the arc melting is terminated to cool the silica glass layer (step S103). In the cooling, the crucible may be cooled naturally, or a cooling gas may be blown onto the inner surface of the crucible to quench the crucible. By adjusting the blowing conditions of the cooling gas in accordance with the position of the crucible, the distribution of the residual stress in the quartz glass crucible is determined.
When the silica glass crucible 1 is cooled, the semi-molten layer and the residual layer of silica powder formed on the outer surface 10o of the crucible act as a buffer against the pressure caused by the thermal shrinkage of the carbon mold. When the silica powder is completely vitrified, the quartz glass crucible is pressurized due to a difference in thermal shrinkage between the quartz glass crucible and the carbon mold during cooling. However, the presence of the non-fused silica powder between the carbon mold and the quartz glass crucible can alleviate the pressure from the carbon mold.
Thereafter, trimming and edge processing of the quartz glass crucible are performed (step S104). As shown in fig. 4(a) and (b), the height of the crucible is adjusted by cutting off a part of the upper end side of the sidewall 10a of the silica glass crucible 1 taken out from the carbon mold during the trimming. In the edge processing, the inner and outer peripheral edges of the upper end surface of the peripheral edge of the crucible are chamfered to form a tapered surface. When the quartz glass crucible 1 is lifted and conveyed by vacuum suction as described above, a vacuum suction device is attached to the peripheral upper end surface 10d of the crucible. Therefore, the peripheral upper end surface 10d requires flatness required for vacuum suction.
As shown in fig. 4(b), when the edge of the upper end face of the peripheral edge of the crucible is chamfered, it is preferable that the inner peripheral edge and the outer peripheral edge are each double-chamfered. That is, after the 1 st tapered surface E1 is formed by chamfering the inner and outer peripheral edges once, the 2 nd tapered surface E2 is formed by chamfering the edge of the 1 st tapered surface E1 twice. By such an arrangement, the number and size of cracks generated at the upper end of the peripheral edge of the crucible can be greatly reduced. In addition, the double chamfer of the edge of the peripheral edge upper end may be only at the inner peripheral edge or only at the outer peripheral edge. Further, the secondary chamfering may be performed only on the upper end side of the peripheral edge. The chamfer angle on the inner surface 10i side (the angle formed by the peripheral edge end surface 20d and the 1 st tapered surface E1 on the inner surface 10i side) is preferably 25 to 80 degrees.
< upper end of periphery >
In the present embodiment, the flatness of the peripheral upper end surface 10d of the quartz glass crucible 1 is preferably 0.01mm to 5 mm. This is because when the flatness is larger than 5mm, the degree of vacuum in the crucible is not increased, and vacuum suction is difficult, and the crucible may fall down on the way even when lifted. Further, when the flatness is smaller than 0.01mm, the vacuum suction of the crucible is too strong and the crucible is difficult to be detached. Further, it is difficult to process the sheet to have a flatness of 0.01mm or less, and it is not preferable from the viewpoint of production cost.
"flatness" is an index indicating the degree of smoothness (uniformity) of a plane, and is defined as "the magnitude of deviation of a planar body from a geometrically correct plane" in JIS. That is, as shown in fig. 5(a), the flatness G is obtained as the distance between the planes P1 and P2 when the plane portion P0 of the object to be measured converges without going out from between the two parallel planes P1 and P2.
The flatness can be calculated by a method such as "maximum vibration flatness" or "maximum tilt flatness". The maximum vibration flatness is obtained by setting a plane passing through 3 points separated as far as possible on the plane of the object and calculating the maximum value of the deviation as flatness. The maximum tilt flatness is calculated as a flatness value of a gap generated when the target plane is sandwiched between two parallel planes.
Fig. 5(b) is a graph showing an example of the measurement result of the flatness of the peripheral upper end face. In this measurement, a flat plate serving as a reference plane is horizontally placed on the peripheral edge upper end surface 10d, and the size of a gap generated between the peripheral edge upper end surface and the back surface of the flat plate is measured over the entire periphery of the peripheral edge. As a result, the variation in height of the peripheral upper end surface 10d is obtained over the entire circumference. As shown in the figure, the change in height of the peripheral upper end face 10d is superimposed with a small surface roughness over a large fluctuation, and the difference between the minimum value and the maximum value of the height of the peripheral upper end face 10d is the flatness G.
The quartz glass crucible 1 having the flatness G of the peripheral upper end surface 10d of 5mm or less can be manufactured by, for example, rotating a blade at the time of trimming or by reducing the crucible feed speed. The rotating speed of the rotating blade and the crucible during trimming is slightly different according to the size of the crucible, and the rotating speed of the crucible is preferably 1.5 to 150m/min, and more preferably 10 to 50 m/min. The rotational speed of the rotary blade is preferably 900 to 2400m/min, and more preferably 1200 to 1800 m/min. The direction of rotation of the rotating blade and the crucible is preferably the same. In order to suppress the edge chipping, it is preferable to sufficiently maintain the moisture content in the wet state.
FIG. 6 is a schematic view for explaining the inclination angle of the opening face at the upper end of the peripheral edge of the silica glass crucible 1.
As shown in FIG. 6, the angle θ (inclination angle of the opening face Sa) of the opening face Sa at the upper end of the peripheral edge of the quartz glass crucible 1 with respect to the horizontal plane S0 is preferably 0.01 ° or more and 5 ° or less, and particularly preferably 3 ° or less. In other words, the angle θ formed by the central axis (vertical axis) of the crucible defined by the cylindrical sidewall 10a, the upper edge of the peripheral edge, and the normal to the opening surface Sa is preferably 5 ° or less.
For example, when the opening face Sa at the upper end of the peripheral edge is inclined to a large degree, the central axis of the crucible is inclined to a large degree instead of the horizontal posture of the cover 30 when the quartz glass crucible 1 is lifted by vacuum suction by the vacuum suction cover 30. When the crucible in such a state is set in the single crystal pulling apparatus, the crucible is set in a state of being inclined with a tilt maintained, and is used. In the single crystal pulling apparatus, a quartz glass crucible 1 is accommodated in a carbon susceptor. The carbon susceptor has a cavity matching the shape of the crucible, so that the crucible is held in the carbon susceptor in an obliquely inclined posture. When the central axis of the crucible is inclined obliquely in this manner and is disposed in the carbon susceptor, the crucible rotates eccentrically in the single crystal pulling step, and pulling of the single crystal from the molten liquid in the crucible is unstable, which affects the single crystal yield and crystal quality. However, if the inclination angle of the opening surface of the crucible is 5 ° or less, the yield of single crystals and the quality of crystals can be prevented from being lowered.
The inclination angle of the opening surface Sa at the upper end of the peripheral edge of the quartz glass crucible 1 can be determined from the spatial coordinates of 3 points on the upper end surface 10d of the peripheral edge. In this case, the inclination angle of the opening face Sa can be accurately obtained based on the measurement result of the 3D shape measuring apparatus that measures the three-dimensional shape of the quartz glass crucible 1.
The number of cracks at the upper end of the periphery of the silica glass crucible 1 is preferably 20 or less. The size of the crack is preferably 0.01mm to 10mm, and particularly preferably 1 mm. When the number of cracks is more than 20, the degree of vacuum in the crucible cannot be sufficiently increased during vacuum suction, and the probability of dropping the lifted crucible becomes high. Further, when the size of the crack is larger than 10mm, the crack is easily extended during vacuum suction, and thus a fine crucible piece (silica glass piece) falls into the crucible to cause dislocation of the single crystal.
The quartz glass crucible 1 having the number of cracks at the upper end of the peripheral edge of 20 or less and the size of the cracks of 0.01 to 10mm can be realized by double chamfering the upper end face of the peripheral edge of the quartz glass crucible by cutting the edge as described above. The double chamfering is a method of chamfering the inner peripheral side angle and the outer peripheral side angle of the peripheral edge upper end surface 10d once and then chamfering the two angles of the inner peripheral side tapered surface and the two angles of the outer peripheral side tapered surface twice. By such processing, the number and size of the cracks at the upper end of the peripheral edge can be sufficiently reduced.
The presence or absence and size of the crack at the upper end of the peripheral edge can be checked visually or automatically by an image processing apparatus. When the light hits a portion where a crack is generated, the posture of reflection of the light is different from that of the surroundings, and therefore, the presence or absence of the crack can be easily recognized.
As described above, since the inclination angle of the opening surface at the upper end of the peripheral edge with respect to the horizontal plane is 5 ° or less in the quartz glass crucible 1 of the present embodiment, the inclination of the central axis of the crucible when the crucible is lifted by vacuum suction can be suppressed. Therefore, the crucible can be set substantially vertically in the single crystal pulling apparatus, and eccentric rotation of the crucible in the single crystal pulling process can be prevented.
Further, since the flatness of the upper end face of the peripheral edge of the quartz glass crucible 1 of the present embodiment is 5mm or less, the degree of vacuum in the crucible can be increased when the crucible is lifted by vacuum suction, and the reliability when the crucible is lifted can be improved.
Further, in the quartz glass crucible 1 of the present embodiment, since the number of cracks at the upper end of the peripheral edge is 20 or less and the size of the cracks is 10mm or less, the degree of vacuum in the crucible can be increased when the crucible is lifted up, and the crucible can be held more reliably.
While the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention, and these are also encompassed in the scope of the present invention.
Examples
< evaluation of flatness of peripheral Upper end face >
Next, the falling rate of the crucible when the vacuum suction operation was repeated 100 times for each sample of the quartz glass crucible was measured. In the evaluation of whether or not the crucible fell, the case where the crucible fell within one hour after the crucible was lifted by vacuum suction was regarded as falling, and the case where the crucible did not fall even after one hour passed was regarded as not falling. As a result, as shown in table 1, the falling rates of examples 1 and 2 were 0%, the falling rate of comparative example 1 was 5%, and the falling rate of comparative example 2 was 15%.
[ TABLE 1 ]
| Crucible sample | Flatness of peripheral upper end face | Falling rate in 100-time repetition of vacuum |
| ＃ | ||
| 1 | 2mm | 0% |
| ＃2 | 5mm | 0% |
| ＃3 | 6mm | 5% |
| ＃4 | 8mm | 15% |
< evaluation of the inclination Angle of the open face of the crucible >
Samples # 5 to # 8 of quartz glass crucibles in which the inclination angles of the opening surfaces of the peripheral upper ends of the crucibles were different were prepared, and the inclination angles of the opening surfaces were measured. As a result, as shown in Table 2, the inclination angles of the opening surfaces of the samples # 5 to # 8 of the quartz glass crucible were 3.5 °, 4.7 °, 5.8 °, and 6.5 °, respectively.
[ TABLE 2 ]
| Crucible sample | Inclination angle of opening surface of crucible | Falling rate in 100-time repetition of vacuum adsorption test |
| ＃5 | 3.5° | 0% |
| ＃6 | 4.7° | 0% |
| ＃7 | 5.8° | 4% |
| ＃8 | 6.5° | 8% |
Next, the falling rate of the crucible when the vacuum suction operation was repeated 100 times with respect to each sample of the quartz glass crucible was measured. As a result, as shown in Table 3, the falling rates of samples # 5 and # 6 were 0%, the falling rate of sample # 7 was 4%, and the falling rate of sample # 8 was 8%.
< evaluation of the number and size of cracks at the upper end of the periphery >
Samples # 9 to # 12 of quartz glass crucibles in which the number and size of cracks at the upper end of the periphery of the crucible were different were prepared, and the maximum values of the number and size of cracks at the upper end of the periphery of the crucibles were measured. As a result, as shown in Table 3, the number of cracks in the quartz glass crucible samples # 9 to # 12 was 10, 19, 18, 22 and 20, respectively. In examples 5 and 6 and comparative examples 5, 6 and 7, the maximum sizes of cracks were 6mm, 10mm, 15mm, 9mm and 12 mm.
Next, the state of the crack after repeating the vacuum adsorption operation for each quartz glass crucible 100 times was evaluated. As a result, no increase in cracks was observed in samples # 9 and # 10. On the other hand, an increase in cracks was observed in samples # 11, # 12 and # 13.
[ TABLE 3 ]
| Crucible sample | Number of cracks | Maximum value of crack | Crack growth after 100 repetitions of vacuum sorption testing |
| ＃9 | 10 are provided with | 6mm | Is free of |
| ＃10 | 19 are provided with | 10mm | Is free of |
| ＃11 | 18 are provided with | 15mm | Is provided with |
| ＃12 | 22 are provided | 9mm | Is provided with |
| ＃13 | 20 are provided with | 12mm | Is provided with |
< evaluation of surface roughness of peripheral upper end face >
Samples # 14 to # 17 of quartz glass crucibles having different surface roughnesses of peripheral upper end faces of the crucibles were prepared, and arithmetic mean roughnesses of the peripheral upper end faces were measured. As a result, as shown in Table 4, the arithmetic mean roughness Ra of samples # 14 to # 17 of the quartz glass crucible was 22 μm, 490 μm, 510 μm, and 680 μm, respectively.
[ TABLE 4 ]
| Crucible sample | Surface roughness Ra (mum) of the peripheral upper end surface of the crucible | Falling rate in 100-time repetition of vacuum adsorption test |
| ＃14 | 20 | 0% |
| ＃15 | 490 | 0% |
| ＃16 | 510 | 5% |
| ＃17 | 680 | 11% |
Next, the dropping rate of the crucible when the vacuum suction operation was repeated 100 times for each sample of the quartz glass crucible was measured. As a result, as shown in Table 4, the falling rates of samples # 14 and # 15 were 0%, the falling rate of sample # 16 was 5%, and the falling rate of sample # 17 was 11%.
Description of the reference numerals
1 Quartz glass crucible
10a side wall part
10b bottom
10c corner
10d peripheral upper end face
10i inner surface
10o outer surface
11 transparent layer
12 air bubble layer
15 build-up layer of silica powder
15a build-up layer of natural silica powder
15b build-up layer of synthetic silica powder
20 carbon mould
21 air vent
22 arc electrode
30 vacuum adsorption cover
E1 taper surface No. 1
E2 taper surface 2
Theta the angle of inclination of the opening face.
Claims (36)
1. A quartz glass crucible is characterized in that,
has a cylindrical side wall portion, a bottom portion, and a corner portion provided between the side wall portion and the bottom portion,
the inclination angle of the opening surface at the upper end of the peripheral edge of the side wall portion with respect to the horizontal plane is 0.01 DEG to 5 deg.
2. The quartz glass crucible according to claim 1,
the flatness of the peripheral upper end surface of the side wall portion is 0.01mm to 5 mm.
3. The quartz glass crucible according to claim 1,
the number of cracks at the upper end of the periphery is 20 or less,
the size of the cracks is 0.01mm to 10 mm.
4. The quartz glass crucible according to any one of claims 1 to 3,
is provided with a transparent layer and a bubble layer,
the transparent layer is made of silica glass containing no bubbles and forms the inner surface of the crucible,
the bubble layer is made of silica glass containing a plurality of bubbles, and is provided outside the transparent layer, and the bubble content of the transparent layer is 0.1vol% or less.
5. The quartz glass crucible according to claim 4,
the side wall portion has a side wall upper portion extending downward from the upper end of the peripheral edge and having a height of 150mm to 200mm, and a side wall lower portion extending downward from the side wall upper portion,
the lower part of the side wall has the transparent layer and the bubble layer,
the upper part of the side wall has the bubble layer and does not have the transparent layer.
6. The quartz glass crucible according to claim 5,
the bubble content in the vicinity of the crucible inner surface at the upper part of the side wall is larger than 0.1% and not more than 3%.
7. The quartz glass crucible according to claim 4,
the number density of bubbles in the bubble layer is 20/cm3Above 300/cm3The following.
8. The quartz glass crucible according to claim 4,
the average diameter of the bubbles in the bubble layer is 20 to 100 [ mu ] m.
9. The quartz glass crucible according to claim 4,
the bubble content of the transparent layer is 0.05vol% or less.
10. The quartz glass crucible according to claim 4,
the bubble content of the transparent layer on the side wall portion is higher than the bubble content of the transparent layer on the bottom portion,
the bubble content of the transparent layer at the corner is higher than the bubble content of the transparent layer at the bottom.
11. The quartz glass crucible according to claim 4,
the transparent layer has a synthetic transparent layer made of silica glass obtained by melting synthetic silica powder and a natural transparent layer made of silica glass obtained by melting natural silica powder, and the bubble content of the synthetic transparent layer is lower than the bubble content of the natural transparent layer.
12. The quartz glass crucible according to claim 4,
the bubble content of the transparent layer on the bottom portion is 4/5 or less of the bubble content of the transparent layer on the side wall portion.
13. The quartz glass crucible according to any one of claims 1 to 3,
the side wall portion has a higher infrared transmittance than the bottom portion,
the bottom portion has an infrared transmittance higher than that of the corner portion.
14. The quartz glass crucible according to any one of claims 1 to 3,
the infrared transmittance of the bottom portion is smaller from the center of the bottom portion toward the corner portion.
15. The quartz glass crucible according to any one of claims 1 to 3,
the infrared transmittance of the side wall portion decreases from above to below the side wall portion.
16. The quartz glass crucible according to any one of claims 1 to 3,
the total length of the distance from the center of the bottom to the maximum thickness of the crucible in the direction from the center of the bottom to the upper end of the peripheral edge of the inner surface of the crucible is 0.35 to 0.65.
17. The quartz glass crucible according to claim 16,
the corner portion has the maximum wall thickness.
18. The quartz glass crucible according to claim 16,
the maximum wall thickness of the crucible is 1.5 to 5% of the diameter of the crucible.
19. The quartz glass crucible according to claim 16,
the portion having the smallest infrared transmittance is within a range of + -30 mm from the maximum thickness position in a direction from the center of the bottom of the inner surface of the crucible toward the upper end of the peripheral edge.
20. The quartz glass crucible according to claim 16,
the thickness of the bottom part is increased from the center of the bottom part to the corner part.
21. The quartz glass crucible according to claim 4,
the distance from the center of the bottom to the maximum thickness of the transparent layer is 0.35-0.65 of the total length from the center of the bottom to the upper end of the periphery of the inner surface of the crucible along the direction from the center of the bottom to the upper end of the periphery.
22. The quartz glass crucible according to claim 4,
the transparent layer has a thickness of 1mm or more of 90% or more of the whole.
23. The quartz glass crucible according to claim 4,
the thickness of the transparent layer is largest at the corner.
24. The quartz glass crucible according to claim 4,
the rate of change in the thickness of the transparent layer is greatest at the corner.
25. The quartz glass crucible according to claim 4,
the rate of change in the thickness of the transparent layer is 9.8mm/cm or less.
26. The quartz glass crucible according to any one of claims 1 to 3,
comprising a synthetic layer made of silica glass obtained by melting synthetic silica powder and a natural layer made of silica glass obtained by melting natural silica powder,
the synthetic layer has a thickness of 0.5 times or less the thickness of the natural layer.
27. The quartz glass crucible of claim 26,
the thickness of the composite layer is 30% or less of the thickness of the crucible.
28. The quartz glass crucible of claim 26,
the thickness of the composite layer of the sidewall portion becomes thicker downward.
29. The quartz glass crucible according to any one of claims 1 to 3,
the side wall portion is open on the outside, and the height from the upper end of the peripheral edge to the maximum outer diameter position of the crucible/the height of the crucible is 0.3 or less.
30. The quartz glass crucible according to any one of claims 1 to 3,
the inner surface roughness is less than the outer surface roughness.
31. The quartz glass crucible according to any one of claims 1 to 3,
the surface roughness of the peripheral upper end surface of the side wall portion is 0.01 μm or more and 500 μm or less.
32. The quartz glass crucible according to any one of claims 1 to 3,
the OH group concentration on the inner surface of the crucible is 250ppm or less.
33. The quartz glass crucible according to any one of claims 1 to 3,
further comprises a crystallization accelerator-containing coating film formed on the inner surface and/or the outer surface of the crucible,
the film thickness of the crystallization accelerator-containing coating film is 1mm or less.
34. The quartz glass crucible according to any one of claims 1 to 3,
the crystallization accelerator coated or doped on the inner surface and/or the outer surface of the crucible is a group 2 element, an alkali metal or a group 13 element.
35. The quartz glass crucible according to any one of claims 1 to 3,
the outermost side of the crucible is provided with a semi-molten layer.
36. A quartz glass crucible is characterized in that,
has a cylindrical side wall portion, a bottom portion, and a corner portion provided between the side wall portion and the bottom portion,
the number of cracks at the upper end of the periphery is 20 or less,
the size of the cracks is 0.01mm to 10 mm.
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|---|---|---|---|
| CN202022692088.1U CN214937960U (en) | 2020-11-19 | 2020-11-19 | Quartz glass crucible |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202022692088.1U CN214937960U (en) | 2020-11-19 | 2020-11-19 | Quartz glass crucible |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115504653A (en) * | 2022-09-15 | 2022-12-23 | 德清三明坩埚有限公司 | Thermal shock cracking resistant clay crucible and preparation process thereof |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115504653A (en) * | 2022-09-15 | 2022-12-23 | 德清三明坩埚有限公司 | Thermal shock cracking resistant clay crucible and preparation process thereof |
| CN115504653B (en) * | 2022-09-15 | 2024-01-12 | 德清三明坩埚有限公司 | Preparation process of clay crucible with thermal shock cracking resistance |
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