KR102342039B1 - Quartz glass crucible - Google Patents

Abstract

A quartz glass crucible capable of producing a low-oxygen single crystal while preventing the generation of dislocations in a silicon single crystal is provided.
The quartz glass crucible 1 is made of a synthetic quartz molten glass containing bubbles, a sealing layer 11 constituting the inner surface of the quartz glass crucible 1, and a bubble-free synthetic quartz molten glass, , a synthetic transparent layer 12 formed on the outside of the sealing layer 11, and a natural transparent layer 13 made of natural quartz molten glass that does not contain air bubbles and formed on the outside of the synthetic transparent layer 12, and containing air bubbles It is made of natural quartz molten glass and has a natural bubble layer 14 formed on the outside of the natural transparent layer 13 , and the bubble content of the sealing layer 11 is higher than that of the synthetic transparent layer 12 .

Description

Quartz glass crucible

The present invention relates to a quartz glass crucible, and more particularly, to a quartz glass crucible used for pulling up a silicon single crystal by the Czochralski method (CZ method).

A quartz glass crucible (silica glass crucible) is used for production of a silicon single crystal by the CZ method. In the CZ method, a polycrystalline silicon raw material is heated in a quartz glass crucible to produce a silicon melt, a seed crystal is immersed in the silicon melt, and the seed crystal is gradually pulled up while rotating the crucible. to grow According to the CZ method, a single crystal with a large diameter can be grown, and the mass productivity of a silicon single crystal can be improved.

Regarding a quartz glass crucible, for example, in Patent Document 1, the maximum layer thickness of the synthetic quartz glass inner layer is 20 to 80% of the maximum thickness of the corner portion, and accordingly, the inner layer of the straight body portion and the bottom portion is A quartz glass crucible is described which is formed thinner than the inner layer of the corner and the inner layer of synthetic quartz glass at the corner is the thickest.

In Patent Document 2, in order to suppress thermal convection in the silicon melt and to prevent vibration of the surface of the melt from occurring, a translucent outer layer made of natural quartz glass and containing a large number of air bubbles and synthetic quartz glass, A quartz glass crucible having a three-layer structure is described by providing a semi-transparent intermediate layer comprising a plurality of bubbles and made of synthetic quartz glass between the transparent inner layers of substantially inorganic cells.

In Patent Document 3, the thickness of the opaque layer in the corner is 25% or more and 80% or less of the total thickness of the opaque layer and the transparent layer, and the thickness of the opaque layer in the straight part and the bottom part is 10% or more of the total thickness of the opaque layer and the transparent layer 25 %, and wherein the thickness of the opaque layer in the corners is greater than in the straights and at the bottom.

In Patent Document 4, the inner surface of the wall of the crucible is made of a transparent layer, and the outer surface of the wall is made of an opaque layer, and the thickness of the transparent layer in the curved portion of the crucible is 0.5 mm or more thicker than the transparent layer in the other portions, and conversely, the transparent layer in the curved portion is opaque A quartz crucible for pulling up silicon single crystals is disclosed, in which the thickness of the layer is 0.5 mm or more thinner than the opaque layer in other portions.

Patent Document 5 describes a quartz glass crucible in which a synthetic inorganic foam layer, a natural inorganic foam layer, a natural foam layer, and an unmelted particle layer are sequentially formed from the inner surface side of the crucible. Further, in a method for manufacturing a quartz crucible, it is described that the coating layer formed on the inner surface of the crucible in the first step of the crucible melting process is removed by sublimation.

(Patent Document 1) Japanese Patent No. 5252157 (Patent Document 2) Japanese Patent Laid-Open No. 2001-348294 (Patent Document 3) Japanese Patent Laid-Open No. 2016-193809 (Patent Document 4) Japanese Patent Laid-Open No. 8-301693 (Patent Document 5) Japanese Patent Laid-Open No. 2010-143818

In recent years, with the large diameter of silicon single crystal and the lengthening of the crystal pulling process, it is necessary for the quartz glass crucible to withstand use for a long time. In addition, the thermal load of the crucible is increasing as the thermal insulation performance of the parts in the pulling furnace is increased.

However, the conventional quartz glass crucible cannot maintain its shape under a thermal environment of 1400° C. or higher when pulling up a silicon single crystal, and deformation of the crucible such as buckling or falling inward occurs, and accordingly, the liquid level of the silicon melt Changes in level, breakage of crucibles, and contact with parts in the furnace become problems. In addition, cristobalite is precipitated on the inner surface of the crucible in contact with the silicon melt, and the outer periphery becomes a brown precipitate (brown ring). When this Brown ring peels off and is introduced into a silicon single crystal being grown, it becomes a factor of dielectric dislocation. In particular, since peeling of the Brown ring is promoted by deformation of the crucible and dislocations are easily generated, it is required to prevent deformation of the crucible as much as possible.

In addition, since the inner surface of the crucible in contact with the silicon melt is gradually lost during the single crystal pulling process, the silicon single crystal grown by the CZ method contains a large amount of oxygen supplied from the crucible. On the other hand, in order to improve the quality of semiconductor devices, in recent years, it is required to uniform the oxygen concentration in the silicon single crystal (especially the oxygen concentration in the pulling axis direction), and a quartz glass crucible capable of satisfying such a demand is desired. In addition, the surface of the melt may vibrate due to the reaction between the crucible and the silicon melt, and when the vibration of the hot water surface occurs, the seed crystal cannot be deposited. The probability increases.

Accordingly, it is an object of the present invention to provide a quartz glass crucible that is not easily deformed and can lower the rate of dislocation generation.

In order to solve the above problems, the quartz glass crucible for pulling up a silicon single crystal according to the present invention is made of a synthetic quartz molten glass containing air bubbles, and a sealing layer constituting the inner surface of the quartz glass crucible, and air bubbles A synthetic transparent layer made of a synthetic quartz molten glass not containing It is made of natural quartz molten glass containing

Brown rings are likely to occur on the outermost surface of the crucible that has been subjected to arc melting, and growth and melting of brown rings occur simultaneously during crystal pulling. rises However, in the quartz glass crucible according to the present invention, since a sealing layer is formed on the inner surface of the crucible and there are bubbles in the sealing layer, dissolution loss of the sealing layer is easy to proceed. , and thus the rate of generation of dislocations can be reduced.

In the present invention, the thickness of the sealing layer is preferably 0.1 mm or more and 2.0 mm or less. When the thickness of the sealing layer is within the above range, it is possible to suppress the vibration of the melt surface and the growth of Brown rings in the initial stage of the crystal pulling process. In addition, since the sealing layer melts and disappears before starting the process for growing the straight body of the single crystal, it is possible to prevent the dielectric dislocation of the single crystal caused by the sealing layer.

In the present invention, the bubble content of the sealing layer is preferably 0.1 vol% or more and 5.0 vol% or less, and more preferably 0.1 vol% or more and 3.0 vol% or less. In this case, the cell number density of the seal layer is less than 15 / cm ³ or more to 300 / cm ^3, average cell diameter of the sealing layer is more preferably 100 μm or less than 0.2 μm. When the bubble content, bubble number density, and average bubble diameter of the sealing layer are within the above ranges, the inner surface of the crucible crystallizes (precipitation of cristobalite) and thus the dielectric dislocation of the single crystal caused by exfoliation can be prevented, and the molten metal vibration can be suppressed.

It is preferable that the bubble content of the sealing layer is lower than that of the natural bubble layer. Accordingly, it is possible to suppress the occurrence of pinholes. In addition, it is possible to prevent the temperature of the inner surface of the crucible from being excessively lowered because the infrared transmittance of the sealing layer is greatly reduced. Incidentally, a pinhole is a microcavity in a crystal generated when a gas or the like in a silicon melt is introduced into a silicon single crystal, and is a cause of device failure.

The quartz glass crucible according to the present invention is made of natural quartz molten glass containing a plurality of bubbles, further comprising a crystal hardened layer formed outside the natural bubble layer, and alkali metal and alkaline earth contained in the crystal hardened layer It is preferable that the concentration of the element of the metal or earth metal is higher than that of the natural bubble layer. In this case, the concentration of the alkali metal, alkaline earth metal or earth metal element contained in the crystal hardened layer is preferably 10 ppm or more higher than that of the natural cell layer, and particularly preferably 20 ppm or more. According to this configuration, it is possible to promote crystallization of the outer surface of the crucible to improve the strength of the crucible, and to suppress the dislocation of the single crystal due to the deformation of the crucible. In addition, by reducing the infrared transmittance by crystallization of the outer surface of the crucible, it is possible to suppress the temperature increase of the inner surface of the crucible, and it is possible to suppress the supply of oxygen due to dissolution loss of the crucible.

The quartz glass crucible according to the present invention has a cylindrical side wall portion, a curved bottom portion, and a corner portion positioned between the side wall portion and the bottom portion and having a greater curvature than the bottom portion, and the thickness of the corner portion is the sidewall It is preferable that the thickness of the synthetic transparent layer is thicker than the thickness of the part and the bottom part, and the thickness of the synthetic transparent layer of the corner part is thicker than the thickness of the synthetic transparent layer of the side wall part and the bottom part. In particular, the maximum thickness of the corner portion is preferably 1.1 times or more, and more preferably 1.5 times or more, the average thickness of the side wall portions. By making the thickness of the corner portion 1c sufficiently thicker than that of other portions, the strength of the entire crucible can be improved, and deformation such as buckling and sinking of the crucible can be suppressed. In addition, since the inner surface of the crucible has the highest temperature at the corner and the contact time with the silicon melt is long, the amount of dissolution loss is larger than that of other parts. However, by increasing the thickness of the corner portion and further increasing the thickness of the synthetic transparent layer in the corner portion sufficiently, exposure of the natural bubble layer can be prevented, and impurity contamination of the single crystal and dislocation can be prevented. Furthermore, if the synthetic transparent layer is thick, it is possible to sufficiently maintain a distance at which impurities in the natural layer are diffused to the inner surface of the crucible. Accordingly, it is possible to prevent delamination of cristobalite or contamination of the silicon single crystal due to the diffusion of impurities in the natural layer to the inner surface of the crucible.

Advantageous Effects of Invention According to the present invention, it is possible to provide a quartz glass crucible that is not easily deformed and can lower the rate of generation of dislocations in single crystals.

1 is a schematic cross-sectional view showing the structure of a quartz glass crucible according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an enlarged part of a side wall portion (part E) of the quartz glass crucible of FIG. 1 .
It is a schematic diagram for demonstrating the manufacturing method of a quartz glass crucible.
4(a) to (d) are diagrams for explaining a process of forming a quartz glass layer.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described in detail, referring an accompanying drawing.

1 is a schematic cross-sectional view showing the structure of a quartz glass crucible according to an embodiment of the present invention. Also, FIG. 2 is a schematic cross-sectional view showing an enlarged part of a side wall portion (part E) of the quartz glass crucible of FIG. 1 .

As shown in Fig. 1, a quartz glass crucible 1 is a bottomed cylindrical container for supporting a silicon melt, and includes a cylindrical side wall portion 1a, a gently curved bottom portion 1b, and a side wall portion. It has a corner part 1c which is located between 1a and the bottom part 1b and has a larger curvature than the bottom part 1b.

The present invention is applicable to crucibles of all diameters, including crucibles with a small diameter of 14 inches (about 350 mm), preferably 24 inches (600 mm) or more, and more preferably 32 inches (about 800 mm) or more. This large-diameter crucible is used for pulling up a large silicon single crystal ingot with a diameter of 300 mm or more, and it is required that it is not deformed well even after using it for a long time. In recent years, as the size of the crucible is increased due to the size of the silicon single crystal, and the length of the pulling process is lengthened, the thermal environment of the crucible is becoming severe, and improving the durability of the large crucible is an important problem.

The thickness of the crucible is slightly different depending on the part. The thickness of the side wall of a crucible of 14 inches or more is 6 mm or more, the thickness of the side wall part 1a of a crucible of 24 inches or more is 7 mm or more, and the side wall part of a large crucible of 32 inches or more ( The thickness of 1a) is preferably 10 mm or more, and the thickness of the side wall portion 1a of the large crucible of 40 inches (about 1000 mm) or more is 13 mm or more. This is because a large-capacity crucible needs a sufficient thickness not to be deformed by the pressure from a large amount of silicon melt. The thickness of the side wall portion 1a of the crucible is generally constant, but tends to be slightly thinner at the upper end than at the lower end.

The thickness of the corner portion 1c of the quartz glass crucible 1 is preferably thicker than that of the side wall portion 1a or the bottom portion 1b. In particular, the maximum thickness of the corner portion 1c is preferably 1.1 times the average thickness of the side wall portion 1a, and more preferably 1.5 times or more.

The quartz glass crucible 1 is heated and softened during crystal pulling, and is in a state easily deformed by the pressure from the silicon melt and the weight of the crucible. In particular, the degree of softening of the portion below the liquid level of the silicone melt is large, and swelling (swelling) of the inner surface of the corner portion is likely to occur. When the crucible is deformed, the brown ring formed on the inner surface of the crucible is peeled off, causing dislocation of the silicon single crystal. In addition, since the inner surface of the crucible has the highest temperature at the corner and the contact time with the silicon melt is long, the amount of dissolution loss is greater than that of other portions, which causes an increase in the oxygen concentration in the single crystal.

However, by making the thickness of the corner part 1c thicker than other parts, the strength of the whole crucible can be improved, deformation such as buckling and sinking of the crucible can be suppressed, and in particular, swelling of the inner surface of the corner part can be suppressed. can Furthermore, since the temperature of the inner surface of the crucible becomes relatively low because the thickness of the corner part 1c of the crucible is thick, the melting loss of a crucible can be suppressed.

As shown in Fig. 2, the quartz glass crucible 1 according to the present embodiment has a five-layer structure, and from the inside of the crucible, a sealing layer 11, a synthetic transparent layer 12, a natural transparent layer 13, a natural bubble layer ( 14), and the crystal hardened layer 15 has a structure in which it is provided in order.

The sealing layer 11 is a synthetic quartz molten glass layer containing air bubbles, and suppresses the growth of brown rings generated on the inner surface of the crucible in the initial stage of the pulling process of silicon single crystal (liquid deposition process - necking process). Together with this, it serves to prevent the vibration of the silicon melt. Brown rings are easily generated on the outermost surface of the crucible subjected to arc melting, and when the brown rings are peeled off, the probability of generating dislocations in a single crystal increases. In addition, if hot water vibration occurs in the process of depositing seed crystals, it is impossible to fuse the seed crystals with the melt. In addition, if the molten metal surface vibration occurs in the necking process for narrowing the crystal diameter, the crystal diameter is not stable, and there is a possibility that dislocations may occur during the single crystal. Furthermore, when the hot water surface vibration occurs, the brown rings generated on the surface of the crucible due to the vibration and the quartz pieces on the surface of the crucible are easily peeled off. However, when the sealing layer 11 is provided on the inner surface of the crucible, it is possible to promote the dissolution loss of the inner surface of the crucible while suppressing the molten metal vibration of the silicon melt, and the sealing layer 11 before the brown ring on the inner surface of the crucible grows large. ) can annihilate the Brown Ring.

The synthetic quartz molten glass layer refers to a quartz glass layer formed using a synthetic quartz raw material (synthetic silica raw material). Synthetic quartz is, for example, a silica raw material synthesized by hydrolysis of silicon alkoxide. In general, synthetic quartz has a lower concentration of metal impurities and a higher concentration of OH groups than natural quartz. For example, the content of each metal impurity contained in the synthetic quartz is less than 0.05 ppm, and the content of the OH group is 30 ppm or more. Whether or not it is synthetic quartz can be comprehensively judged from the concentrations of OH groups and a plurality of metal impurities. As described above, since synthetic quartz has fewer impurities than natural quartz, elution of impurities from the crucible into the silicon melt can be prevented.

The sealing layer 11 is designed so that the synthetic transparent layer 12 is exposed by melting before the start of pulling the straight body of the silicon single crystal. This is because, if the sealing layer 11 does not disappear at the start of pulling the straight body, dislocations may occur due to Brown rings being introduced into the single crystal. Therefore, it is preferable that the thickness of the sealing layer 11 is 0.1-2.0 mm. When the sealing layer 11 is smaller than 0.1 mm, the sealing layer 11 disappears immediately, and the effect of providing the sealing layer 11 cannot be obtained. In addition, when the sealing layer 11 is larger than 2.0 mm, there is a fear that the sealing layer 11 will not disappear before the start of pulling up the straight body. The sealing layer 11 only needs to be located on at least the sidewall portion 1a, thereby suppressing the crystallization of the inner surface of the crucible and the vibration of the molten metal of the silicon melt.

The bubble content of the sealing layer 11 is preferably higher than that of the synthetic transparent layer 12 or the natural transparent layer 13 and lower than that of the natural bubble layer 14. In particular, the bubble content of the sealing layer 11 is 0.1 to 5.0 vol%. It is preferable that it is 0.1-3.0 vol%, and it is more preferable that it is. In this case, the cell number density is preferably 15 to ^{300 pieces/cm 3 .} Moreover, it is preferable that it is 0.2-100 micrometers, and, as for an average cell diameter, it is preferable that it is 0.2-50 micrometers. When the cell content, cell number density, and average cell diameter in the sealing layer 11 are within the above ranges, the dissolution rate of the inner surface of the crucible can be increased, and cristobalite generated on the surface of the sealing layer 11 grows and peels off Dielectric dislocation of single crystals can be prevented by annihilating cristobalite in the sealing layer 11 before being formed. As for the bubble content of the sealing layer 11, it is preferable that the upper side of a side wall part is higher than the lower part of a side wall part.

When the bubble content, the bubble number density, and the average bubble diameter of the sealing layer 11 exceed the above ranges, there is a fear that pinholes are generated during crystallization. That is, when the inner surface of the crucible is melted, many bubbles enter the silicon melt in the crucible, and these bubbles rise to the melt convection and are introduced into the solid-liquid interface, thereby generating pinholes in the single crystal. Alternatively, when the bubble is introduced into the single crystal by being peeled off from the inner surface of the crucible during pulling up of the straight body after the bubble adheres to the inner surface of the crucible, pinholes are generated in the single crystal.

The second layer, the synthetic transparent layer 12 , is a bubble-free synthetic quartz molten glass layer and is located outside the sealing layer 11 . The synthetic transparent layer 12 is provided in order to prevent dislocation of the silicon single crystal or the generation of pinholes in the single crystal due to the influence of air bubbles, and also to prevent contamination of the silicon single crystal with impurities. The synthetic transparent layer 12 constitutes the inner surface of the crucible wall after the sealing layer 11 melts and disappears, and is a layer in contact with the silicon melt, so it is required to have high purity in order to prevent contamination of the silicon melt.

The thickness of the synthetic transparent layer 12 is preferably 0.1 to 10 mm, particularly preferably 0.5 to 10 mm. The synthetic transparent layer 12 is set to an appropriate thickness for each part of the crucible so that the natural transparent layer 13 is not completely lost during the pulling up process of the single crystal and thus the natural transparent layer 13 is not exposed. For example, the thickness of the synthetic transparent layer of a crucible of 14 inches or more exists about 0.5 mm. The synthetic transparent layer 12 is preferably provided in the entire crucible from the side wall portion 1a to the bottom portion 1b of the crucible together with the natural transparent layer 13 . However, it is also possible to omit the formation of the transparent layer in the upper end (rim portion) of the crucible that is not in contact with the silicon melt.

When the synthetic transparent layer 12 does not contain air bubbles, it means that air bubbles have been removed to such an extent that it appears transparent at first glance. The synthetic transparent layer 12 needs only to have a bubble content such that the yield of single crystals does not decrease due to crucible fragments when the bubbles are ruptured, the bubble content rate is less than 0.1 vol%, and the bubble number density is 15 pieces/cm ³ or less, and the average cell diameter is preferably 50 µm or less.

The third layer, the natural transparent layer 13 , is a natural quartz molten glass layer that does not contain air bubbles, and is located outside the synthetic transparent layer 12 . That is, the synthetic transparent layer 12, which is the second layer, and the natural transparent layer 13, which is the third layer, are the same transparent layer, and are different from the synthetic transparent layer 12 using synthetic raw materials in that the raw material used is a natural raw material. The concentration of impurities contained in the transparent layer 13 is higher than that of the synthetic transparent layer 12 . Since the natural transparent layer 13 has a higher viscosity than the synthetic transparent layer 12, it is possible to suppress the propagation of thermal expansion of the natural bubble layer 14 provided on the outer surface side of the crucible to the inner surface side of the crucible. In addition, by providing the boundary between the synthetic quartz molten glass layer and the natural quartz molten glass layer in the transparent layer, it is possible to prevent peeling of the synthetic quartz molten glass layer due to heat load. When the natural transparent layer 13 does not have bubbles, it means that the bubbles are removed to the extent that it appears transparent at first glance, and the natural transparent layer 13 only needs to have the same transparency as the synthetic transparent layer 12 .

The natural quartz molten glass layer refers to a quartz glass layer formed using a natural quartz raw material. Natural quartz is a natural raw material, such as natural quartz and a silica stone. In general, natural quartz has a higher concentration of metal impurities and a lower concentration of OH groups than synthetic quartz. For example, the content of Al contained in natural quartz is 1 ppm or more, the content of alkali metals (Na, K and Li) is respectively 0.05 ppm or more, and the content of the OH group is less than 80 ppm. Whether it is natural quartz can be comprehensively determined from the concentration of OH groups and a plurality of metal impurities. Since natural quartz has a higher viscosity at high temperature than synthetic quartz, it is possible to increase the heat-resistant strength of the entire crucible. In addition, natural quartz is cheaper than synthetic quartz, which is advantageous in terms of cost.

In the initial stage of crystal pulling (until the start of shoulder growth), the brown ring is still small, and since the sealing layer constitutes the inner surface of the crucible, dissolution of the inner surface of the crucible is easy to proceed. While still small, it dissipates by exfoliation or dissolution. As described above, although the number of brown rings decreases in the middle of the crystal pulling, it is presumed that a part of the brown rings are growing without extinction, and the single crystals are dislocated by peeling the brown rings that do not disappear during growth of the straight body. Brown ring peeling tends to occur when the inner surface of the crucible is deformed. However, by interposing the natural transparent layer 13 between the synthetic transparent layer 12 and the natural bubble layer 14 , deformation of the inner surface of the synthetic transparent layer 12 can be suppressed and peeling of the brown ring can be prevented.

The fourth layer, the natural bubble layer 14, is a natural quartz molten glass layer containing a large number of bubbles. The natural bubble layer 14 is provided to heat the silicon melt in the crucible as uniformly as possible by dispersing radiant heat from the heater disposed outside the crucible. Since the natural bubble layer 14 has a larger heat capacity than the transparent layer, it is possible to stably control the temperature of the silicon melt. In addition, it is possible to improve the thermal insulation of the crucible, and it is possible to suppress the increase in the oxygen concentration of the single crystal due to the sagging of the inner surface of the crucible due to the excessively high temperature of the inner surface of the crucible, the generation and growth of Brown rings, and the dissolution loss of the crucible. . Furthermore, it suppresses the deterioration of the inner surface of the crucible by alleviating the rapid change in heat received from the heater when the crucible is raised or lowered, the heater power is turned on, or the single crystal is transferred from the shoulder to the straight body, and the oxygen introduced into the silicon single crystal is rapidly reduced. change can be suppressed. It is preferable that the natural bubble layer 14 is provided in the whole crucible from the side wall part 1a of the crucible to the bottom part 1b.

The bubble content of the natural bubble layer 14 is greater than the bubble content of the sealing layer 11, the synthetic transparent layer 12 and the natural transparent layer 13, preferably 0.2 to 5 vol%, and 1 to 4 vol% more preferably. It is because the function of the natural bubble layer 14 cannot be exhibited when the bubble content rate of the natural bubble layer 14 is 1 vol% or less, and heat retention becomes inadequate. In addition, when the bubble content of the natural bubble layer 14 exceeds 5 vol%, the crucible is greatly deformed due to the expansion of the bubble, and there is a risk that the single crystal yield may decrease, and furthermore, the heat transfer property is insufficient. because it is done In particular, when the bubble content of the natural bubble layer 14 is 1 to 4%, the deformation of the crucible can be further prevented, and the heat transfer property can be further improved.

The fifth layer, the hardened crystal layer 15, is a natural quartz molten glass layer containing a large amount of a crystallization accelerator. The crystallization accelerator is an element of an alkali metal, alkaline earth metal or earth metal, and examples thereof include Li, Na, K, Mg, Ca, Sr, Ba, Al, Ga and the like. When a large amount of the crystallization accelerator is included, the strength of the crucible can be increased by promoting the crystallization of the outer surface of the crucible, or the viscosity of the quartz glass softened under high temperature can be increased to prevent deformation such as buckling and collapse of the crucible. In addition, the crystal hardened layer 15 has the effect of lowering the infrared transmittance of the crucible, and it is possible to moderate the rapid thermal change received from the heater, thereby suppressing the rapid change in the oxygen concentration in the silicon single crystal. The total thickness of the natural bubble layer 14 and the crystal hardened layer 15 is a value obtained by subtracting the total thickness of the sealing layer 11, the synthetic transparent layer 12, and the natural transparent layer 13 from the thickness of the crucible. vary according to

The portion where the total thickness of the synthetic transparent layer 12 and the natural transparent layer 13 is maximum is formed in the corner portion 1c, and the thickness of the synthetic transparent layer 12 of the corner portion 1c is the sidewall portion 1a and It is preferably thicker than the thickness of the synthetic transparent layer 12 of the bottom portion 1b. The corner portion 1c of the crucible is the portion where the inner surface of the crucible has the highest temperature, and the contact time with the silicon melt is long, so the amount of dissolution loss is greater than that of other portions. However, by increasing the thickness of the corner portion 1c and further increasing the thickness of the synthetic transparent layer 12 of the corner portion 1c sufficiently, exposure of the natural bubble layer 14 can be prevented, and contamination of single crystal impurities and dislocation can be prevented.

It is a schematic diagram for demonstrating the manufacturing method of a quartz glass crucible. 4(a) to (d) are views for explaining the process of forming the quartz glass layer.

As shown in Fig. 3, the quartz glass crucible 1 according to the present embodiment can be manufactured by a so-called rotational molding method. In the rotary mold method, a natural quartz powder 21, a normal natural quartz powder 22, and a synthetic quartz powder 23 to which a crystallization accelerator is added are sequentially deposited on the inner surface 30i of the rotating mold 30 to deposit raw material quartz. A powder deposition layer 20 is formed (refer to Fig. 4(a)). The raw quartz powder is adhered to the inner surface 30i of the mold 30 by centrifugal force and remains at a fixed position, and the shape of the crucible is maintained.

Next, the arc electrode 31 is installed in the mold 30 , and the deposited layer 20 of raw quartz powder is arc-melted from the inner surface 30i side of the mold 30 . Specific conditions such as heating time and heating temperature need to be appropriately determined in consideration of conditions such as the raw material and size of the crucible. At this time, the amount of bubbles in the molten quartz glass is controlled by evacuating the deposited layer 20 of raw quartz powder from a plurality of ventilation holes 32 provided in the inner surface 30i of the mold 30 .

Arc heat is gradually transferred from the inside to the outside of the deposited layer 20 of the raw quartz powder to melt the raw quartz powder, so by changing the pressure reduction condition at the timing when the raw quartz powder starts to melt, the sealing layer 11 , the synthetic transparent layer 12 , the natural transparent layer 13 , the natural bubble layer 14 , and the crystal hardened layer 15 can be made separately. When the reduced pressure melting is performed to strengthen the pressure at the timing at which the quartz powder is melted, the arc atmosphere gas is not trapped in the glass, resulting in a quartz glass containing no air bubbles. In addition, if normal melting (atmospheric pressure melting) is performed in which the reduced pressure is weakened at the timing at which the quartz powder is melted, the arc atmosphere gas is trapped in the glass, resulting in a quartz glass containing many bubbles.

Specifically, at the start of arc melting, the sealing layer 11 containing air bubbles is formed by slightly weakening the suction force from the ventilation hole 32, etc. (refer to FIG. 4(b)), and then the suction force is By strengthening, the synthetic transparent layer 12 and the natural transparent layer 13 are sequentially formed (refer to Fig. 4(c)). Thereafter, the natural bubble layer 14 and the crystal hardened layer 15 are sequentially formed by weakening the attraction force (FIG. 4(d)).

After that, arc heating is finished and the crucible is cooled. As described above, a quartz glass crucible in which a sealing layer 11, a synthetic transparent layer 12, a natural transparent layer 13, a natural bubble layer 14, and a crystal hardened layer 15 are sequentially provided from the inside to the outside of the crucible wall ( 1) is completed.

As described above, the quartz glass crucible 1 according to the present embodiment has a sealing layer 11, a synthetic transparent layer 12, a natural transparent layer 13, a natural bubble layer 14, and crystal hardening from the inner surface side of the crucible. Since the layers 15 have a structure in which they are sequentially provided, and the bubble content of the sealing layer 11 is higher than that of the synthetic transparent layer 12 and lower than that of the natural bubble layer 14, It can promote dragon-handling. Accordingly, it is possible to prevent dislocation of the single crystal due to the crystallization and exfoliation of the inner surface of the crucible, thereby reducing the rate of dislocation of the single crystal. In addition, since the thickness of the sealing layer 11 is 0.1 mm or more and 2.0 mm or less, the sealing layer melts and disappears before starting the straight body growth process of the silicon single crystal, and the synthetic transparent layer is exposed to constitute the inner surface of the crucible, so that the dielectric of the single crystal It can prevent stomach upset and impurity contamination.

As mentioned above, although the preferred embodiment of the present invention has been described, the present invention is not limited to the above-described embodiment, and various changes are possible without departing from the main gist of the present invention, and they are also included within the scope of the present invention. of course it is

For example, in the above embodiment, the five-layer structure of the sealing layer 11, the synthetic transparent layer 12, the natural transparent layer 13, the natural bubble layer 14, and the crystal hardened layer 15 was set. It is also possible to omit the crystal hardened layer 15 to have a four-layer structure of the sealing layer 11 , the synthetic transparent layer 12 , the natural transparent layer 13 , and the natural bubble layer 14 .

(Example)

<Consideration 1: A Study of Crucibles with Different Layer Structures>

After pulling the silicon single crystal by the CZ method using a quartz glass crucible having a diameter of 32 inches, the yield of the single crystal and the degree of deformation of the crucible after use were evaluated. In this evaluation test, a plurality of three types of crucible samples A1 to A3 having different layer structures were prepared, respectively, and pulling up of a plurality of silicon single crystals was performed using these crucibles. The results are shown in Table 1.

Crucible
Sample crucible structure crucible deformation crystal yield A1 3-layer crucible (synthetic transparent layer + natural transparent layer + natural bubble layer) littleness 60% or less A2 3-layer crucible (sealing layer + synthetic transparent layer + natural bubble layer) middle 70% or less A3 4-layer crucible (sealing layer + synthetic transparent layer + natural transparent layer + natural bubble layer) littleness 80% or more

As shown in Table 1, in Sample A1, which has a three-layer structure of synthetic transparent layer/naturally transparent layer/natural bubble layer and does not have a sealing layer, crystal pulling could not be performed, or even if it could be done, single crystal The crystal yield was set to 60% or less by dislocation.

In addition, in crucible sample A2 having a three-layer structure of a sealing layer/synthetic transparent layer/natural bubble layer, the increase in molten metal vibration and brown rings could be suppressed by the action of the sealing layer, but the crystal yield was 70% or less. This deterioration of the crystal yield is thought to be due to the absence of the natural transparent layer, and thus the deformation due to thermal expansion of the natural bubble layer propagates to the synthetic transparent layer, causing deformation of the inner surface and peeling of the brown ring.

Furthermore, in Sample A3 having a four-layer structure of sealing layer/synthetic transparent layer/naturally transparent layer/natural bubble layer, the crystal yield was 80% or more. In Sample A3, the action of the sealing layer can suppress the vibration of the water surface and the increase of the Brown ring, and furthermore, the action of the natural transparent layer suppresses the deformation of the synthetic transparent layer due to the expansion of the natural bubble layer, and the deformation of the synthetic transparent layer It is thought that peeling of a brown ring can be suppressed.

<Consideration 2: Consideration of the thickness of the sealing layer of a 4-layer crucible>

A plurality of samples B1 to B5 of a four-layer crucible having different sealing layer thicknesses were prepared, respectively, and pulling up of a silicon single crystal was performed using these crucibles. The results are shown in Table 2.

Crucible
Sample sealing layer thickness crystal yield B1 0.05 mm 65% or less B2 0.1 mm 80% or more B3 0.5 mm 80% or more B4 2.0 mm 80% or more B5 2.5 mm 70% or less

As shown in Table 2, in Sample B1 with a sealing layer thickness of 0.05 mm, similar to Sample A1 without a sealing layer, crystal pulling could not be performed or even if it was possible, dielectric dislocation of single crystals was not possible due to severe tangential vibration. The crystal yield was 65% or less. In addition, dislocation occurred in sample B5 with a thickness of the sealing layer of 2.5 mm, and the crystal yield was 70% or less. On the other hand, dielectric dislocation did not occur in the crucible samples B2 to B4 in which the thickness of the sealing layer was 0.1 to 2.0 mm. From these results, it was found that, if the thickness of the sealing layer was within the range of 0.1 to 2.0 mm, the effect of suppressing the dielectric dislocation of the single crystal by the sealing layer could be obtained. When the sealing layer is excessively thick, it is considered that the crystal yield is lowered because there is a residual insoluble material in the sealing layer during growth of the straight body part of the single crystal and the brown ring is easily peeled off.

<Consideration 3: Consideration of cell content, cell density, and average cell diameter of the sealing layer>

A plurality of samples C1 to C3 of a four-layer crucible having different conditions of air bubbles included in the sealing layer were prepared, respectively, and silicon single crystals were pulled using these crucibles. The results are shown in Table 3.

Crucible
Sample Bubble condition of sealing layer crystal yield pinhole
incidence rate C1 Bubble content:
0.1 to 5.0 vol%;
Bubble count density:
15-300 pieces/cm ³ ,
Average cell diameter:
0.2-100 μm 80% or more 0.1% or less C2 Bubble content:
less than 0.1 vol%;
Bubble count density:
less than 15 pcs/cm ^3,
Average cell diameter:
less than 0.2 μm 70% or less 0.1% or less C3 Bubble content:
greater than 5.0 vol%;
Bubble count density:
more than 300 pcs/cm ^3;
Average cell diameter:
>100 μm 80% or more 3% or more

As shown in Table 3, in Sample C1 having a bubble content of 0.1 to 5.0 vol%, a cell density of 15 to 300 cells/cm ³ , and an average cell diameter of 0.2 to 100 μm, the crystal yield was 80% or more. On the other hand, in sample C2 with a bubble content of less than 0.1 vol%, a cell density of less than 15 cells/cm ³ , and an average cell diameter of less than 0.2 μm, the same as in Sample A1 without a sealing layer, since the hot water surface vibration is severe, crystal pulling is performed. It was impossible or even if it was possible, the crystal yield was 70% or less due to dislocation of the single crystal.

Further, in sample C3 having a bubble content of more than 5.0 vol%, a cell density of more ^{than 300 cells/cm 3} , and an average cell diameter of more than 100 μm, dislocation was suppressed and the crystal yield was 80% or more, but a wafer cut out from a single crystal was inspected, and pinholes were found. The pinhole occurrence rate of samples C1 and C2 was 0.1% or less, whereas the pinhole occurrence rate of sample C3 was 3% or more. In addition, the pinhole occurrence rate can be calculated|required by calculating the number of pinhole defect wafers/(the number of pinhole acceptance wafers + the number of pinhole defect wafers). When the number of bubbles included in the sealing layer is excessively large, dislocation of the single crystal can be prevented, but it is considered that pinholes are easily generated in the single crystal. From the above results, if the cell content is 0.1 to 5.0 vol%, the cell density is 15 to 300 cells/cm ³ , and the average cell diameter is within the range of 0.2 to 100 μm, the dielectric dislocation of the single crystal can be suppressed by the sealing layer. It was found that an effect could be obtained.

<Consideration 4: Consideration of the presence or absence of a hardened crystal layer>

A plurality of samples D1 of a four-layer crucible without a crystal hardened layer and a sample D2 of a five-layer crucible with a hardened crystal layer were each prepared, and pulling up of a silicon single crystal was performed using these crucibles. The results are shown in Table 4.

Crucible
Sample crucible structure crucible deformation crystal yield D1 4-layer crucible (sealing layer + synthetic transparent layer + natural transparent layer + natural bubble layer) littleness 80% or more D2 5-layer crucible (sealing layer + synthetic transparent layer + natural transparent layer + natural bubble layer + crystal hardened layer) very small 85% or more

As shown in Table 4, in Sample D1 having a four-layer structure of sealing layer / synthetic transparent layer / natural transparent layer / natural bubble layer and without a crystal hardened layer, the deformation of the crucible was small, and the crystal yield was 80% or more. On the other hand, in sample D2 having a five-layer structure of sealing layer/synthetic transparent layer/naturally clear layer/natural bubble layer/crystal hardened layer, the deformation of the crucible was very small, and the crystal yield was 85% or more. In the sample D2 in which the crystal hardened layer was additionally provided, it is thought that the deformation of the crucible was sufficiently suppressed, thereby further enhancing the effect of suppressing the peeling of the brown ring.

<Consideration 5: Consideration of maximum corner thickness (maximum/average sidewall)>

Samples E1 to E8 of four-layer crucibles having different maximum thickness ratios (maximum thickness of corner portions/average thickness of side wall portions) of the corner portions of the crucible were prepared, and pulling up of a silicon single crystal was performed using these crucibles. The results are shown in Table 5.

Crucible
Sample corner
maximum thickness
ratio synthetic transparent layer
thickness of Exposure of natural clear layer transform &
swelling decision
transference number E1 0.5 Side wall part, bottom part>Corner part has exist has exist 60% or less E2 0.5 Side wall part, bottom part<corner part none has exist 70% or less E3 One Side wall part, bottom part>Corner part has exist has exist 60% or less E4 One Side wall part, bottom part<corner part none has exist 70% or less E5 1.1 Side wall part, bottom part>Corner part has exist none 70% or less E6 1.1 Side wall part, bottom part<corner part none none 80% or more E7 1.5 Side wall part, bottom part>Corner part has exist none 70% or less E8 1.5 Side wall part, bottom part<corner part none none 80% or more

As shown in Table 5, in Sample E1, where the maximum thickness ratio of the corner portion was 0.5 and the thickness of the synthetic transparent layer on the sidewall portion and the bottom portion was greater than the thickness of the corner portion, the natural transparent layer was formed due to the disappearance of the synthetic transparent layer and peeling of cristobalite due to impurity diffusion. exposed, and the brown ring was peeled off due to deformation (swelling) of the crucible, and the crystal yield became 60% or less. In addition, in sample E2, where the maximum thickness ratio of the corner part was 0.5 and the thickness of the synthetic transparent layer on the sidewall part and the bottom part was smaller than the corner part, the natural transparent layer was not exposed, but the brown ring was peeled off due to deformation (swelling) of the crucible, The crystal yield was 70% or less.

Sample E3 in which the corner maximum thickness ratio was 1, and the thickness of the synthetic transparent layer in the side wall and bottom portions was greater than that in the corner portion, gave the same result as Sample E1. Sample E4 in which the corner portion maximum thickness ratio was 1, and the thickness of the synthetic transparent layer in the sidewall portion and the bottom portion was smaller than that in the corner portion gave the same result as sample E2.

Sample E5, in which the maximum thickness ratio of the corner portion was 1.1, and the thickness of the synthetic transparent layer in the sidewall portion and the bottom portion was greater than that of the corner portion, gave the same results as Samples E1 and E3, and the crystal yield was 70% or less. On the other hand, in Sample E6, where the maximum thickness ratio of the corner portion was 1.1 and the thickness of the synthetic transparent layer on the sidewall portion and the bottom portion was smaller than the thickness of the corner portion, the natural transparent layer was not exposed, and no deformation of the crucible occurred. Accordingly, the crystal yield of Sample E6 was 80% or more.

Sample E7 in which the maximum thickness ratio of the corner portion was 1.5 and the thickness of the synthetic transparent layer in the side wall portion and the bottom portion was larger than that in the corner portion gave the same result as sample E5, and the crystal yield was 70% or less. In addition, the sample E8 having a maximum thickness ratio of the corner portion of 1.5 and the thickness of the synthetic transparent layer in the side wall portion and the bottom portion being smaller than the thickness of the corner portion gave the same result as the sample E6, and the crystal yield was 80% or more.

From the above results, the crystal yield of samples E6 and E8 in which the maximum thickness ratio of the corner part was 1.1 or more and the thickness of the synthetic transparent layer of the side wall part and the bottom part was smaller than that of the corner part was 80% or more, and the exposure of the natural transparent layer or the deformation of the crucible ( It was found that dislocation caused by swelling) can be suppressed.

1 Quartz Glass Crucible
1a side wall
1b bottom
1c corner
11 sealing layer
12 synthetic transparent layer
13 Natural transparent layer
14 natural bubble layer
15 crystal hardened layer
20 Sedimentary layer of raw quartz powder
21 Natural quartz powder with added crystallization accelerator
22 Natural Quartz Powder (Normal Natural Quartz Powder)
23 Synthetic Quartz Powder
30 mold
30i mold inside
31 arc electrode
32 ventilation holes

Claims (22)

A quartz glass crucible for pulling up silicon single crystals, comprising:
A sealing layer made of a synthetic quartz molten glass containing air bubbles and constituting an inner surface of the quartz glass crucible;
A synthetic transparent layer made of a synthetic quartz molten glass that does not contain air bubbles and formed outside the sealing layer;
A natural transparent layer made of natural quartz molten glass that does not contain air bubbles and formed outside the synthetic transparent layer;
It is made of natural quartz molten glass containing a plurality of bubbles, and a natural bubble layer formed on the outside of the natural transparent layer,
The bubble content rate of the sealing layer is a quartz glass crucible, characterized in that higher than the bubble content rate of the synthetic transparent layer. The method according to claim 1,
The thickness of the sealing layer is 0.1 mm or more and 2.0 mm or less, a quartz glass crucible. The method according to claim 1,
The bubble content of the sealing layer is 0.1 vol% or more and 5.0 vol% or less, a quartz glass crucible. 3. The method according to claim 2,
The bubble content of the sealing layer is 0.1 vol% or more and 5.0 vol% or less, a quartz glass crucible. 4. The method according to claim 3,
The density of the number of cells in the sealing layer is 15 pieces/cm ³ or more and 300 pieces/cm ³ or less, a quartz glass crucible. 5. The method according to claim 4,
The density of the number of cells in the sealing layer is 15 pieces/cm ³ or more and 300 pieces/cm ³ or less, a quartz glass crucible. 4. The method according to claim 3,
The average cell diameter of the sealing layer is 0.2 μm or more and 100 μm or less, a quartz glass crucible. 5. The method according to claim 4,
The average cell diameter of the sealing layer is 0.2 μm or more and 100 μm or less, a quartz glass crucible. 6. The method of claim 5,
The average cell diameter of the sealing layer is 0.2 μm or more and 100 μm or less, a quartz glass crucible. 7. The method of claim 6,
The average cell diameter of the sealing layer is 0.2 μm or more and 100 μm or less, a quartz glass crucible. The method according to claim 1,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 3. The method according to claim 2,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 4. The method according to claim 3,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 5. The method according to claim 4,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 6. The method of claim 5,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 7. The method of claim 6,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 8. The method of claim 7,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 9. The method of claim 8,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 10. The method of claim 9,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 11. The method of claim 10,
The bubble content rate of the sealing layer is lower than the bubble content rate of the natural bubble layer, quartz glass crucible. 21. The method of any one of claims 1 to 20,
A crystal hardened layer made of natural quartz molten glass containing a plurality of bubbles and formed outside the natural bubble layer,
The concentration of an alkali metal, alkaline earth metal or earth metal element contained in the crystal hardened layer is higher than that of the natural bubble layer, a quartz glass crucible. 21. The method of any one of claims 1 to 20,
It has a cylindrical side wall portion, a curved bottom portion, and a corner portion positioned between the side wall portion and the bottom portion and having a greater curvature than the bottom portion,
The thickness of the corner part is thicker than the side wall part and the bottom part,
and a thickness of the synthetic transparent layer in the corner portion is thicker than the synthetic transparent layer in the sidewall portion and the bottom portion.

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