JP2001233629A - Method of producing quartz glass crucible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent inhibiting the quartz glass from forming single crystal, when the crucible is pulled up, by pulling up the crucible so that the bubbles occluded in the quartz crucible may not be broken even under high heat load. SOLUTION: When the starting powder is molten in the mold 1, H2 gas and O2 gas are introduced immediately after the start of arc discharge to remove the graphite component of the electrodes and the impurities in the starting quartz powder whereby the contamination of the crucible products with the graphite and the impurities can be inhibited and the expansion coefficient of the bubbles can be suppressed and the pressure in the bubbles can be reduced. In addition, a helium gas is fed from the mold to the sedimentary layers of the quartz powder formed in the mold 1 thereby replacing the gas in the voids in the sedimentary layers with helium. Since the bubbles in the opaque layers are made less expandable to inhibit the reduction of the thermal conductivity, the temperature increase in the crucible can be suppressed on use and resultantly, the bubbles in the clear layers can be prevented from bursting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a quartz glass crucible, and more particularly to a method of manufacturing a quartz glass crucible used for pulling a semiconductor single crystal and capable of improving the yield of the semiconductor single crystal.

[0002]

2. Description of the Related Art As a method of manufacturing a semiconductor single crystal such as silicon, a pulling method (Czochralski) in which a seed crystal serving as a nucleus is immersed in a melt surface of a molten semiconductor material and a single crystal is grown from the seed crystal. A quartz glass crucible is used for melting a semiconductor material. In recent years, in order to reduce the manufacturing cost of pulling a single crystal, multi-pulling and pulling of a large-diameter silicon single crystal have been performed, and accordingly, the quartz glass crucible used has been increasing in diameter.

When the diameter of a quartz glass crucible increases and the amount of semiconductor material melted therein increases, the melting time increases and the pulling time increases. In order to shorten the pulling time, it is conceivable to increase the amount of heat (heat input) provided by the heater. Further, it is preferable that the heat input be large in order to maintain a large amount of the semiconductor material melt at a predetermined temperature.

However, if the heat input is large, the following problems may occur. It is known that in a quartz glass crucible, gas components are mixed in from the atmosphere during the manufacturing process and exist as many bubbles. The bubbles expand when the quartz glass crucible is used at a high temperature, and in particular, the bubbles in the transparent layer of the inner surface layer of the crucible may expand and burst. A piece of quartz glass generated by this rupture may be mixed into the silicon melt, become cristobalite, move by convection in the melt, and adhere to the end of the silicon single crystal being pulled. As a result, the single crystal breaks from the adhered portion, and as a result, the yield of the semiconductor single crystal decreases. This problem is remarkable due to an increase in the amount of heat input due to an increase in the diameter of the quartz glass crucible and an increase in the heat load due to an increase in the pulling time. Bubbles present in the transparent layer are more likely to burst as the number and size of the bubbles are larger and as the degree of expansion of the bubbles at the time of pulling a single crystal is larger.

[0005] As a method of obtaining a glass layer having high transparency by reducing the bubbles contained therein, a method of producing quartz glass by melting silica sand powder in a high-temperature atmosphere is well known. For example, there are so-called hydrogen oxyhydrogen Bernoulli methods, arc Bernoulli methods, plasma Bernouli methods, and the like, depending on the difference in heat sources that form a high-temperature atmosphere. Attempts have been made to apply these melting methods to the manufacture of quartz glass crucibles and to substantially eliminate bubbles in the quartz glass crucible. For example, Japanese Patent Publication No. 4-22861 proposes a method for producing a quartz glass crucible in which a transparent layer is formed on the inner surface portion of a crucible that comes into direct contact with a silicon melt at the time of pulling up by applying the Arc Bernoulli method. I have.

In Japanese Patent Application Laid-Open No. Hei 8-268727, silica sand charged in a melting pot is formed into a bowl by centrifugal force and heated, and a rapid diffusion gas is introduced from the outer surface of the bowl-shaped silica sand. A method for manufacturing a quartz crucible including a step of removing residual gas contained in voids in silica sand by using the method is disclosed. Further, in this quartz crucible manufacturing method, in order to remove residual gas from voids in the silica sand, a vacuum is applied to the bottom of the melting pot of the silica sand to cause a flow of the rapid diffusion gas.

[0007]

In the quartz glass crucible manufacturing method described in the former of the above publications, the heat load increases due to multi-pulling, large diameter silicon single crystal, etc., or the pulling time becomes long. May not be able to respond to the current pulling process. Therefore, even when the heat load is large or the pulling time is long,
There is a demand for a quartz glass crucible in which bubbles in the inner surface layer are less likely to burst.

According to the method for manufacturing a quartz crucible described in the latter publication, the gas remaining in the voids is replaced with a rapid diffusion gas, so that bubbles in the quartz glass crucible are heated during high-temperature heating such as in the production of semiconductor single crystals. Growth prevention can be expected. However, in this manufacturing method, replacement of residual gas such as nitrogen or oxygen is still insufficient, so that bubbles in the opaque layer expand during use, thermal conductivity is deteriorated, and the temperature of the quartz glass crucible tends to increase. . As a result, the bubbles in the transparent layer are easily ruptured.

In general, N trapped in a void
2 etc. have a higher density than H2 which is a rapid diffusion gas. Therefore, due to the density difference between these gases, H
2 will blow through and the replacement will take a long time. Therefore, sufficient replacement is not performed by blowing the rapid diffusion gas for a short time, and a gas such as N2 remains in the void. This residual gas becomes bubbles in the inner surface layer of the quartz glass crucible, and the number of bubbles cannot be substantially reduced.

The tendency to increase the heat input further affects the pulling of the semiconductor single crystal. At the time of pulling, the quartz glass crucible is supported on its outer periphery by a graphite holding member heated by a heater, and heat is applied to the semiconductor material in the quartz glass crucible from the heater through the holding member.

The higher the transparency of the quartz glass crucible, the more effectively the heat from the heater is transferred to the semiconductor material.
However, since the heaters are generally spaced apart from each other, if the quartz glass crucible is completely transparent, the heat from the heaters will propagate linearly to the semiconductor material in the quartz glass crucible, and between the heaters. Heat is not easily transmitted to the semiconductor material. Therefore, in order to transfer heat evenly, the heat rays emitted from the heater are diffused in multiple directions when passing through the quartz glass crucible, so that the distribution is equalized. An opaque layer containing bubbles is formed.

However, when the number of air bubbles in the opaque layer is too large or when the air bubbles are large, it becomes difficult for the heat rays radiated from the heater to pass through to the transparent layer side, and heat is efficiently transferred to the semiconductor melt in the crucible. Not given. In particular, when the size of the bubbles increases due to heating, heat tends to accumulate in the quartz glass crucible due to the decrease in thermal conductivity, and the heat of the quartz glass crucible itself is reduced despite the fact that heat is difficult to be transmitted to the semiconductor melt. Is extremely high.

When the temperature of the quartz glass crucible also rises extremely, devitrification occurs around 1550 ° C. Furthermore, if the heat of the heater is not sufficiently transferred to the semiconductor material melt in the quartz glass crucible, the temperature of the semiconductor material melt may partially decrease, causing icing (partial solidification).

Therefore, the large heat input applied effectively acts on the semiconductor material in the quartz glass crucible and can contribute to pulling up in a short time, and the heat released from the heater is reflected on the heater side to cause an abnormal temperature. Without rising or icing,
In addition, there has been a demand for a quartz glass crucible capable of uniformly transmitting heat from a heater to a semiconductor material contained and a melt thereof.

In the method disclosed in JP-A-8-268727, the degree of vacuum in the mold cannot be increased in a short time because the opening for applying a vacuum is provided only at the bottom of the mold. .

As described above, in order to improve the growth yield of the single crystal, the number and size of bubbles existing in the inner surface layer of the quartz glass crucible and the expansion ratio of the bubbles (before the single crystal is pulled up). Ratio of bubble diameter after and after)
It is desired to reduce. Further, in order to obtain stable thermal conductivity also for the outer surface layer, it is preferable to make existing bubbles hard to expand.

FIG. 2 is a graph showing the results of an investigation on the relationship between the average bubble diameter and the yield of single crystals in a corner portion of a quartz glass crucible, that is, a layer having an inner surface of about 1 mm at the boundary between the bottom and the side wall. The reason for paying attention to the corners is that a large load is applied particularly to the corners when pulling the single crystal, and the bubbles existing in the corners are closely related to the yield of the single crystal.

The sample of the quartz glass crucible used for the investigation has a diameter of 22 inches. The yield is as follows: 100 kg of silicon polycrystal is heated and melted to make the liquid surface about 1430 ° C.
, And a silicon single crystal seed rod is immersed in the molten surface to pull up an 8-inch silicon single crystal.
A test piece was taken from this quartz glass crucible, and as a result of examining the bubble diameter and the single crystal yield in the corner portion, as shown in FIG. 2, when the average bubble diameter was 200 μm or more, the yield of the single crystal decreased. You can see that

According to the present invention, the number, size and expansion of bubbles in a transparent layer are reduced to prevent the rupture of bubbles and improve the yield of semiconductor single crystals, and to reduce the number of bubbles in an opaque layer. It is an object of the present invention to provide a method for manufacturing a quartz glass crucible capable of suppressing the temperature rise of the quartz glass crucible with an appropriate ratio and increasing the thermal efficiency when pulling a semiconductor single crystal.

[0020]

According to the present invention, there is provided a method for producing a quartz glass crucible in which a quartz powder is melted by arc discharge between graphite electrodes arranged in a rotating mold and the crucible is molded. , O2, H2
A first feature is that the method comprises a step of supplying at least one of O, He, and Ne gases, and a step of supplying quartz powder to the inner surface of the mold by passing the supplied gas through the atmosphere. In particular, the second feature is that H2 gas and O2 gas are supplied in the gas supply step.

Further, the present invention has a third feature in that the quartz powder is sprayed into the mold so that the quartz powder is softened in an atmosphere of arc discharge before reaching the inner surface of the mold. There is. Further, the present invention provides a gas supply apparatus, wherein the gas and the quartz powder are supplied through a double cylinder. In particular, the quartz powder is supplied from an inner cylinder and the gas is supplied from an outer cylinder. The fourth feature is that the H2 gas is supplied from the outer cylinder and the fifth feature is that the H2 gas is supplied from the outer cylinder. The sixth feature is that the tip of the inner cylinder of the double cylinder is retracted from the tip of the outer cylinder. Further, the present invention has a seventh feature in that at least quartz powder of the quartz powder and the gas is intermittently supplied while the arc discharge is maintained.

According to these features, impurities such as alkaline earth metals and heavy metals contained in the supplied quartz powder are replaced with a gas such as H2 or burned in a high temperature atmosphere, so that the purity of the quartz powder is increased. . In particular, the supplied O2 gas and H
The two gases allow the inside of the mold to reach a high-temperature atmosphere in which the quartz powder can be melted in a short time, thereby facilitating degassing and suppressing the degree of air bubbles entering the product crucible. Further, the graphite constituting the electrode is easily oxidized easily by the high temperature, so that mixing of the graphite into the product crucible is suppressed. Further, the supplied gas diffuses into the product crucible, and has an effect of reducing the pressure inside the bubbles.

In particular, according to the third feature, since the quartz powder is deposited on the molten surface of the previously formed quartz glass in a softened state, the quartz powder is easily compatible with the fused surface, and thus the quartz powder is Impurities adhering to the surface are easily removed.

According to the fourth and fifth features, since the supplied quartz powder is blown together with the gas, the directivity can be controlled by the direction of the double cylinder. According to the sixth feature, the quartz powder is blown. Is surrounded by gas at the tip of the double cylinder, and has good contact with the gas. Further, according to the seventh feature, a decrease in the temperature of the fused layer of quartz is prevented, and the fused layer continuously reacts with the atmospheric gas, and the removal of impurities that cause bubbles is further promoted.

Further, the present invention has the following features regarding the formation of the opaque layer. First, in a method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge in a rotating mold and a crucible is formed, a step of forming a deposited layer of quartz powder along an inner surface of the mold; Supplying He and / or H2 gas (hereinafter referred to as He gas as a representative) to the deposition layer from a predetermined position in between, starting an arc discharge, and forming a thin film molten layer on the surface of the deposition layer. When formed, the He
An eighth feature is that the step of stopping the supply of gas and evacuating the deposition layer and the step of restarting the supply of He gas when the deposition layer reaches a predetermined degree of vacuum are provided. . According to the eighth feature, He gas is supplied into the void in the vacuum-deposited layer, and the atmosphere in the void is replaced with He.

The present invention also provides a step of, after the deposition layer is formed, covering the upper opening of the mold and evacuating the inside of the mold, and further comprising the steps of: Supplying He gas into the mold, and starting the arc discharge by opening the lid when the pressure in the mold rises to a predetermined value. After opening the lid,
A ninth feature is that the supply of the He gas is continued for a predetermined time. According to the ninth feature, a higher degree of vacuum can be obtained because the mold is sealed with the lid. Therefore, the He gas supplied thereafter sufficiently spreads in the voids of the deposited layer and is sufficiently replaced by the He gas.

The present invention also provides a step of starting the arc discharge after supplying He gas to the deposition layer from a predetermined position between the side wall and the bottom of the mold, and forming a thin film molten layer on the surface of the deposition layer. And a step of exhausting the deposition layer from the upper part of the side wall of the mold while continuing the supply of the He gas. A gas flow can be created, which can have a displacing effect on the entire deposited layer.

Further, according to the present invention, when the thin film molten layer is formed on the surface of the deposition layer, the supply position of the He gas is switched to the upper part of the side wall of the mold, and the He gas is supplied before the arc discharge. The eleventh feature is that the deposition layer is evacuated from a position where the He gas flows from above to below in the deposition layer, and the replacement action can be exerted on the entire deposition layer. .

[0029] The present invention also provides a step of evacuating the inside of the mold by covering the upper opening of the mold with the deposition layer, and a step of forming a side wall of the mold when the inside of the mold reaches a predetermined degree of vacuum. And supplying He gas into the mold from a predetermined position between the bottom and the bottom, and starting the arc discharge by opening the lid when the pressure in the mold rises to a predetermined value. The twelfth feature is that the step of exhausting the deposited layer from the upper part of the side wall of the mold while the supply of the He gas is continued when the thin film molten layer is formed.

Further, the present invention provides a method wherein, after the deposition layer is formed, the upper opening of the mold is covered and the inside of the mold is evacuated, and when the inside of the mold reaches a predetermined degree of vacuum. A step of supplying He gas into the mold from a predetermined position between the side wall and the bottom of the mold, and a step of starting the arc discharge by opening the lid when the pressure in the mold rises to a predetermined value, When a thin film molten layer is formed on the surface of the deposition layer, the supply position of the He gas is switched to the upper part of the side wall of the mold, and exhaust of the deposition layer is performed from the position where the He gas was supplied before the arc discharge. The thirteenth feature lies in the step of
The present invention having the twelfth and thirteenth features operates similarly to the invention having the tenth and eleventh features.

According to the eighth to thirteenth features, since the voids in the deposited layer are replaced with He gas, the quartz glass crucible as a product is heated to a high temperature (14 ° C.) when the semiconductor single crystal is pulled.
Even when the temperature reaches 50 to 1700 ° C.), the expansion of bubbles mixed into the outer surface layer of the quartz glass crucible can be suppressed. As a result, the thermal conductivity of the quartz glass crucible is not impaired, and the abnormal temperature rise of the quartz glass crucible is suppressed.

Further, the present invention provides a method for manufacturing a semiconductor device according to the present invention, further comprising the steps of:
H2, O2, H2 O, He, and N
A fourteenth feature of the present invention comprises a step of supplying at least one gas from the group consisting of e-gas and a step of supplying quartz powder to the inner surface of the mold by passing the supplied gas through the atmosphere. The fifteenth feature is that the quartz powder is sprayed into the mold so that the quartz powder is softened in the arc atmosphere before reaching the inner surface of the mold. The present invention having the fourteenth and fifteenth features is characterized by
It operates in the same manner as the invention according to the thirteenth aspect, and
And it works similarly to the invention having the second feature.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described according to embodiments. The present embodiment provides a means for reducing the number and size of bubbles existing in the transparent layer formed on the inner surface of the quartz glass crucible and for reducing the expansion rate of the bubbles.

First, N2 gas or alkaline earth metal remaining between the particles of quartz powder as a raw material is a source of air bubbles. By cutting these off, the number of air bubbles is reduced and the number of air bubbles is reduced. Reduce the size. In particular,
By introducing one or more of gases such as H2, O2, H2 O, He, Ne and the like in a mixed state, a quartz glass crucible with few bubbles can be obtained. This is because if the above gas is introduced during arc discharge, the temperature inside the mold becomes extremely high. In the conventional arc Bernoulli method in which no gas is introduced, as the temperature in the mold increases, the surface of the raw material first sinters at around 1650 ° C., and then begins to melt when it reaches around 1750 ° C. On the other hand, according to the present embodiment, degassing is facilitated by shortening the time required for the sintering step to reach the molten state in a short time, and the number of air bubbles can be reduced. In particular, when O2 gas and H2 gas are introduced during arc discharge, the inside of the mold easily reaches a high temperature, so that the degree of sintering of the raw material can be reduced in the high temperature atmosphere.

Second, the expansion rate of the bubble is reduced by reducing the pressure inside the bubble. As described above, the expansion rate of bubbles can be reduced by introducing H2 gas or O2 gas during arc discharge. The introduced gas diffuses into the quartz glass crucible and bubbles in the quartz glass crucible and easily dissolves in the quartz glass. H2, H
e and Ne are particularly easy to diffuse and easily dissolve in quartz glass. These gas atoms having a small atomic radius can freely move through the silica matrix in the quartz glass. As a result, it is easily released to the outside of the quartz glass under reduced pressure and high temperature conditions, the internal pressure of the bubbles is reduced, and the expansion of the bubbles is suppressed.

Third, graphite mixed from the graphite electrode is eliminated to reduce the number of bubbles and the expansion rate of the bubbles. Quartz glass crucibles are manufactured by melting and solidifying raw materials in a mold. And the heat of fusion is obtained from the arc discharge by the graphite electrode. Most of the graphite generated from the graphite electrode is combined with O2 in the mold and burns, but a part of the graphite remains in the manufactured quartz glass crucible to form bubbles and increase its expansion rate. That is, the remaining graphite reacts with O2 trapped in bubbles under low pressure and high temperature conditions, that is, under pulling conditions, to generate CO gas and expand the bubbles.

In order to prevent graphite from entering the inner surface of the quartz glass crucible, gases such as H 2, O 2, H 2 O, He, and Ne are introduced during arc discharge.
As described above, graphite is combined with the introduced O2 and burns. However, since the inside of the mold becomes extremely hot due to the introduction of the other gases described above, the graphite is combined with O2 in the air and burns more easily. In particular, H2, O2,
H2 O promotes the oxidation of graphite.

Next, a specific method of manufacturing a quartz glass crucible and a measurement result of the expansion rate of bubbles in the transparent layer of the manufactured quartz glass crucible will be described. In the first embodiment, H2 gas is introduced into the mold. FIG. 1 is a cross-sectional view of a main part showing an apparatus for manufacturing a quartz glass crucible. In the figure, a mold 1 made of metal (preferably stainless steel)
It has a double structure and is water-cooled with cooling water passing through a tube 1B provided on the inner wall 1A. The mold 1 has an inner diameter of 570 mm, and the mold 1 is rotated about a shaft 2 by a rotating device (not shown). A pair of graphite electrodes 4 and 5 are held on a heat shield plate 3 disposed at the upper center of the mold 1.

A double cylinder is formed by the gas nozzle 6 and the introduction pipe 7 for introducing the raw material quartz powder, and this double cylinder is arranged adjacent to the graphite electrode 4. The double cylinder has a quartz powder inlet tube 7 inside and a gas nozzle 6 arranged outside, but the reverse is also possible.
When quartz powder is introduced from the inside of the double cylinder (inner cylinder) and gas is introduced from the outer cylinder (outer cylinder), the tip of the inner cylinder is retracted from the tip of the outer cylinder. If it is set in a state where it is also retracted, the state is such that the gas wraps the quartz powder, and the contact between the two is likely to be sufficient.

In the present embodiment, quartz powder is used as a raw material powder. However, the term “quartz powder” used herein is not limited to quartz, and includes quartz glass crucibles such as quartz, silica sand, etc., including silicon dioxide (silica). Also includes powders of known materials. The inlet 6A of the gas nozzle 6 is connected to a H2 gas pipe or cylinder (not shown), and the upper end of the introduction pipe 7 is connected to a hopper 8 containing quartz powder. In addition, a gas introduction pipe 9 can be additionally provided between the graphite electrodes 4 and 5.

A process of manufacturing a crucible by the manufacturing apparatus having the above-described configuration will be described. First, the mold 1 is rotated, and quartz powder (for example, a particle size of 60 # to 150 #) is introduced into the inner peripheral surface of the mold 1 through the introduction pipe 7. Since the mold 1 is being rotated, the charged quartz powder sticks to the inner peripheral surface of the mold 1 and is deposited by centrifugal force. At this time, the introduction of the quartz powder may be performed by using the introduction pipe 7 or by another device. After a predetermined amount of quartz powder is deposited, a voltage is applied between the graphite electrodes 4 and 5 to cause arc discharge. The quartz powder adhered to the mold 1 is melted by the arc heat, and an opaque layer L1 (see FIG. 1) constituting the outer peripheral surface of the quartz glass crucible is formed.

After the formation of the opaque layer L1, a transparent layer L2 (see FIG. 1) is subsequently formed. When 5 to 10 minutes have passed after the melting of the deposited quartz powder has started, the quartz powder and H2 gas are supplied to the mold 1 through the introduction pipe 7 and the gas nozzle 6. At this time, the supply amount of the quartz powder is preferably, for example, 80 to 160 g / min, and the supply amount of the H2 gas is, for example, 60 to 100 liter / min.

The atmosphere in the vicinity of the arc of the graphite electrodes 4 and 5 is 2000 ° C. or higher (5000 ° C. or higher during the arc), and the quartz powder sprayed in this atmosphere softens. The softened quartz powder is directly transferred onto the opaque layer L1 or once dropped on the bottom of the mold and then lifted up by centrifugal force to deposit on the opaque layer L1 to form the transparent layer L2.

The quartz powder which has been introduced into the vicinity of the arc together with the H 2 gas and softened is replaced with air, moisture and impurities such as alkaline earth metals and heavy metals adhering to the surface thereof by the H 2 gas. Or burning in high temperature to increase the purity. As a result, it is possible to reduce the residual gas that is taken into the transparent layer L2 and is a source of bubbles. In addition, since the residual gas taken in is also replaced by H2 gas having high diffusivity, as described above, the H2 gas can freely move through the silica matrix in the quartz glass. And is easily released to the outside of the quartz glass, and rupture due to expansion of bubbles is unlikely to occur.

In order to reduce the residual gas mixed in the transparent layer L2 as much as possible, the temperature of the fused quartz surface layer is preferably maintained at a high temperature (preferably 2000 ° C. or higher). This is because the higher the temperature, the more the residual gas is released from the molten surface layer into the atmosphere. If quartz powder is continuously introduced, the temperature of the molten surface layer may decrease, so that the quartz powder is preferably sprayed intermittently. For example, after spraying quartz powder and supplying H2 gas for 10 minutes, the spraying of quartz powder is stopped once and the melting operation is continued for another 20 minutes. By repeating this operation, the transparent layer L
Finish 2 to desired thickness. In order to continue the action of the molten surface layer on the residual gas, only the supply of the H2 gas may be continued while the dispersion of the quartz powder is stopped.

With respect to the quartz glass crucible manufactured as described above, the number, size, and expansion coefficient of bubbles were examined. FIG. 3 is a diagram showing the results of investigation on the number and size of bubbles before and after use in a quartz glass crucible according to the manufacturing method according to the present embodiment. Observation of air bubbles before use was performed on 20 samples at a depth of 0.5 mm to 1.5 mm from the inner surface by setting a 20 × microscope at the inner corner portion of the quartz glass crucible.

For observation after use, the corner portion of the quartz glass crucible after use was cut, and the cut surface was cut at room temperature for 30 minutes.
After etching with% ammonium fluoride acid, cleaning was performed with an ultrapure water shower. The observation position was the same as before the observation, and the observation was performed on 20 samples at a depth of 0.5 mm to 1.5 mm from the inner surface of the quartz glass crucible. The quartz glass crucible is C
A sample “after use” was obtained by pulling 100 kg of silicon in 50 hours by the Z method.

As shown in FIG. 3, the maximum size (diameter) of the bubble before use is 51 μm, the minimum is 3 μm, and the average is 13 μm.
m, the maximum size of the bubble after use was 90 μm, the minimum was 9 μm, and the average was 34 μm. The number of bubbles in the quartz glass crucible was 0.14 / mm3 before use,
After use, it was 0.27 pieces / mm3. Thus, the average bubble size after use was 34 μm, and the single crystal yield was 100%, consistent with the results described with respect to FIG.

Next, a description will be given of the results of an investigation on the relationship between the expansion rate of bubbles and the yield. In the above manufacturing method, 13 22-inch quartz glass crucibles were manufactured by changing the amount of H2 gas introduced between 0 and 60 liters / minute. With respect to these quartz glass crucibles, the expansion rate of bubbles (bubble diameter after use / bubble diameter before use) and the yield of single crystallization were investigated, and the relationship between the two was investigated. FIG. 4 is a diagram showing the relationship between the coefficient of expansion and the yield of single crystallization. The use conditions and observation conditions of the quartz glass crucible for investigating the yield of single crystallization are the same as those in the example of FIG.

As shown in FIG. 4, the expansion rates of the bubbles of the 13 types of crucibles are distributed in the range of 1.5 to 3.5. As can be understood from the figure, the single crystallization yield is a good result (100%) in a sample having an expansion coefficient of less than “2.5”.

As described above, according to the present embodiment, the removal of contaminants caused by external factors of the operating environment typified by the entrainment of the air and the further removal of impurities contained in the raw material powder are actively performed. Has been done. As a result, the amount of inert gas confined in the transparent layer of the quartz glass crucible was reduced to the utmost.

Next, a second embodiment of the present invention will be described.
In the first embodiment, the crucible was manufactured by introducing H2 gas. In the second embodiment, O2 gas and H2 gas are introduced. FIG. 5 is a cross-sectional view of a main part showing a manufacturing apparatus of a quartz glass crucible according to the second embodiment, and the same reference numerals as those in FIG. In FIG.
Is formed so that the raw material powder can be supplied through the hopper 8, and a branch pipe or an inlet 70A in the middle thereof for introducing O2 gas.
B. On the other hand, the outer tube of the double cylinder 70, that is, the gas nozzle 6, has an inlet 6A for introducing H2 gas, as in the first embodiment.

As described above, when the quartz powder and the O 2 gas are ejected from the common cylinder, that is, the introduction pipe 70A, the introduction pipe 70A
The feeding direction of the quartz powder can be arbitrarily set according to the direction of the above. However, the present invention is not limited to this, and quartz powder and O2 gas may be injected into the mold 1 using separate nozzles.

In operation, first, the opaque layer L1 is formed as in the first embodiment. After forming the opaque layer L1, a transparent layer L2 (see FIG. 1) is subsequently formed. When 5 to 10 minutes have passed after the melting of the deposited quartz powder has started, quartz powder, O2 gas and H2 gas are supplied to the mold 1 through the double cylinder 70. At this time, as in the first embodiment, the supply amount of the quartz powder is, for example, 80 to 160.
g / min, and the total supply of O2 gas and H2 gas is preferably, for example, 60 to 100 liter / min. The ratio of the supply amounts of the O2 gas and the H2 gas is desirably 1: 6. This is because if the O2 gas is too much, bubbles are rather likely to be generated. When the H2 gas is increased to the maximum, the above ratio can be 1:10.

The quartz powder sprayed in the atmosphere near the arcs of the graphite electrodes 4 and 5 softens and turns into the opaque layer L1.
On the opaque layer L1 by directly transferring to the top of the mold, or once falling to the bottom of the mold, and then rising by centrifugal force to form a transparent layer L2. In particular, O2 gas and H2
Quartz powder that has passed through the atmosphere at a high temperature after the gas has been introduced softens very easily.

The transparent layer L2 made of quartz powder which has been injected into the vicinity of the arc together with the O2 gas and the H2 gas and has been softened contains little residual gas as a source of bubbles. Further, the gas slightly remaining in the transparent layer L2 is easily released to the outside of the quartz glass under reduced pressure and high temperature under a H2-rich environment, as in the case where only the H2 gas is introduced.

As described above, when a quartz glass crucible is manufactured by increasing the flow ratio of H 2 gas, H
2 It is rich. Even if the abundant H2 gas reacts with the O2 gas in the air entering the quartz glass crucible by convection generated during pulling of the semiconductor single crystal to generate water vapor, the quartz glass crucible can still be kept H2 rich. The water vapor generated during the pulling is discharged from the upper part of the quartz glass crucible by the high temperature convection of the arc discharge without contacting the inner surface of the quartz glass crucible.

The results of investigation on the number and size of bubbles before and after use of the quartz glass crucible manufactured in the second embodiment are the same as in the first embodiment. In addition, the expansion rate of the bubbles in the quartz crucible was the same as in the first embodiment.

In the second embodiment, O2 gas is supplied together with the raw material powder from the inner cylinder of the double cylinder, and H 2 gas is supplied from the outer cylinder.
Although the two gases are supplied, the H2 gas may be supplied together with the raw material powder and the O2 gas may be supplied from the outer cylinder. The O2 gas and the H2 gas are not limited to being supplied separately, but may be mixed in advance and the mixed gas may be supplied.

Next, a manufacturing method for stabilizing the thermal conductivity in the outer surface layer, that is, the opaque layer of the quartz glass crucible will be described. In order to stabilize the thermal conductivity of the opaque layer, He gas is supplied from a pot for melting the quartz powder, that is, a mold, and gas in the voids of the quartz powder deposited on the inner wall surface of the mold is replaced with He gas. . The details will be described below with reference to the drawings.

FIG. 6 is a cross-sectional view of a main part of a manufacturing apparatus used in the method of manufacturing a quartz glass crucible according to the third embodiment. The same reference numerals as those in FIG. 1 denote the same or equivalent parts. The end of the cooling water pipe 1B fixed to the inner wall 1A of the hollow portion of the mold 1 is drawn out below the mold 1 and connected to a circulation device (not shown). At the bottom of the inner wall 1A of the mold 1, a hole 10 for passing He as a replacement gas is formed. Note that the He supply hole 10 can be provided not only at the bottom but also at any position between the bottom and the side wall of the mold 1 (see FIG. 9 described later). The hollow portion between the double walls of the mold 1 is filled with He gas supplied from the bottom of the mold 1, and the filled He gas flows through the hole 10 into the inner wall 1.
A penetrates upward. On the other hand, an exhaust hole 11 is provided near the upper end of the mold 1, that is, on the inner wall near the upper opening of the mold.
The hole 11 is connected to a joint 12. The joint 12 has a tube 13 extending below the mold 1 and communicating with a vacuum pump (not shown).
Is connected. The tube 13 may extend downward through a hollow portion in the mold 1.

The inner diameter of the mold 1 is 570 mm as an example.
The mold 1 is rotated by a rotating device (not shown) as shown by an arrow 14. Prior to the generation of an arc between the electrodes 4 and 5, a deposition layer 15 of raw material powder is formed along the wall surface inside the mold 1. Gas nozzle 6
6A inlet is H2 gas pipe or cylinder (not shown)
And the upper end of the introduction pipe 7 is connected to a raw material hopper containing quartz powder, as in the manufacturing apparatus of FIG.

Next, a procedure for manufacturing a quartz glass crucible using the manufacturing apparatus having the above configuration will be described. First, a deposited layer 15 of quartz powder is formed. The particle size and supply amount of quartz powder are the first
This is the same as the embodiment. When the deposition layer 15 having the predetermined thickness is formed, arc discharge is caused between the graphite electrodes 4 and 5 to start melting the deposition layer 15.

Prior to the arc discharge, the supply of He gas to the deposition layer 15 through the hole 10 of the mold 1 is started. The supply rate of He gas is preferably about 30 liters / minute. After supplying He gas for about 5 minutes, arc discharge is performed. One to two minutes after the start of the arc discharge, a thin molten layer is formed on the surface of the deposition layer 15. At the time when the thin film melt layer is formed, the supply of the He gas is stopped, and the unmelted portion of the deposition layer 15 is exhausted through the hole 11. When the inside of the mold 1 reaches a predetermined degree of vacuum (for example, 30 Torr) by evacuation, He is introduced again. It should be noted that a small amount of He gas (less than 10 liters / minute) is supplied during the evacuation without stopping the supply of He gas when the thin film molten layer is formed.
May be continuously supplied.

In the third embodiment, the He gas is introduced when the degree of vacuum is increased.
He gas is effectively absorbed, and the air in the voids (spaces) of the deposition layer 15 is sufficiently replaced by the He gas. By replacing the voids in the deposited layer 15 with the He gas, the bubbles present in the opaque layer formed by melting the deposited layer 15 have a very small amount of N2 gas and O2 gas and a small expansion coefficient. The supply of the He gas restarted after the exhaust may be stopped after a preset time,
A small amount (less than 10 liters / minute) may continue to be supplied.

When an opaque layer of about 10 mm is formed, a transparent layer is formed on the opaque layer, that is, on the inner surface of the quartz glass crucible. The transparent layer is formed in the same manner as in the first embodiment, while supplying H2 gas from the gas nozzle 6 and simultaneously sprinkling quartz powder into the mold 1 through the introduction pipe 7.

FIG. 7 is a diagram showing the results of a study on the number of bubbles, the bubble diameter, and the expansion coefficient in the opaque layer. The observation of the bubbles before and after use was performed in the same manner as in the case of the transparent layer. Things. The unit of the number is
mm3, and the unit of the bubble diameter is μm. As shown in the figure, the number of bubbles and the diameter of bubbles before use are substantially the same between the conventional product and the improved product obtained by the manufacturing method of the third embodiment. In particular, significant improvements are seen. In the transparent layer of the quartz glass crucible according to the third embodiment, the number of bubbles, the bubble diameter,
The expansion coefficient and the like were the same as in the first embodiment.

Next, a modification of the method for forming the opaque layer will be described. 8 and 9 are cross-sectional views of an apparatus used in a manufacturing method according to a modification, showing only a main part of the mold 1.
The electrodes 4, 5 and the cooling water pipe 1B are not shown. 6 denote the same or equivalent parts. In the apparatus according to the fourth embodiment shown in FIG.
Is provided with a bottom hole 10 at the bottom and a side hole 16 at the side.
Is provided. A vacuum pump 18 and a He gas supply source 19 are connected to the bottom of the mold 1 via a switch 17. Further, the mold 1 is covered with a lid 20 before the start of the arc discharge by the electrodes 4 and 5.

In this manufacturing apparatus, after the deposition layer 15 is formed, the lid 20 is put on the upper opening of the mold 1, and the vacuum pump 18 is operated to move the inside of the mold 1 through the bottom hole 10 and the side holes 16. Exhaust. By this exhaust, the mold 1
When the inside reaches a predetermined degree of vacuum (for example, 1 to 5 Torr)
The switch 17 is switched to the He gas supply source 19 side, and He gas is supplied into the mold 1 from the bottom hole 10 and the side hole 16. When the pressure in the mold 1 increases to a predetermined value, for example, when the pressure reaches the atmospheric pressure, the process proceeds to a stage in which the lid 20 is opened to start arc discharge. Even after the lid 20 is opened to start the arc discharge, the supply of the He gas is continued. It is preferable to supply at least until a thin film fusion layer is formed on the surface of the deposition layer 15.

On the other hand, in the apparatus of the fifth embodiment shown in FIG. 9, a bottom hole 10 is provided at the bottom of the inner wall 1A of the mold 1, and a side portion is provided above the hole 16 separately from the hole 16. A top hole 11 is provided, and a side hole 16 communicates with the bottom hole 10. In the apparatus of FIG.
After the deposition layer 15 is formed along the inner surface of the substrate, He gas is supplied to the deposition layer 15 through the side hole 16 and the bottom hole 10 to supply H gas.
After the e-gas is supplied for a predetermined time (for example, 5 minutes), the process shifts to arc discharge. When a thin film melted layer is formed on the surface of the deposition layer 15 by arc discharge, the deposition of the deposition layer 15 is performed through the upper hole 11 on the upper side wall of the mold 1 while the supply of He gas is continued.
Exhaust. The supply and exhaust of the He gas causes a flow of the He gas from the bottom to the top in the deposition layer 15, and the voids in the deposition layer 15 are replaced by the He gas.

The flow of the He gas may be generated from the upper side to the lower side of the deposition layer 15. For example,
Side hole 1 formed between side wall and bottom of mold 1
6. After supplying He gas from the bottom hole 10 to the deposition layer 15 for a predetermined time (for example, 5 minutes), the process proceeds to a stage where arc discharge is started, and when a thin film molten layer is formed on the surface of the deposition layer 15, He The gas supply position is switched to the upper hole 11 on the side wall of the mold 1, and the deposition layer 15 is exhausted from the position where He gas was supplied before the arc discharge, that is, from the bottom hole 10 and the side hole 16 of the mold 1. . This causes a downward flow of He gas. Thus, H
In order to change the positions of supply and exhaust of e-gas, two tubes 21 and 2 drawn from the bottom of the mold 1 are used.
A He gas supply source 19 is connected to 2 via a switch 23.

When a He gas flow is generated in the deposition layer 15 using the apparatus shown in FIG. 9, similarly to the modification shown in FIG. 8, a lid 20 is placed on the mold 1 to form a closed space, and the arc is formed. Prior to generation, the inside may be evacuated, and He gas may be introduced therein to replace the atmosphere with He gas.

Since a film containing water exists around the quartz powder, it is preferable to remove this water in advance. Moisture can be removed by preheating the deposited layer 15 prior to arc generation. For example, a halogen lamp can be installed in the mold 1 facing the deposition layer 15, the atmosphere in the mold 1 can be raised to about 100 ° C., and the deposition layer 15 can be heated during exhaust. By removing the water around the quartz powder in advance, replacement with He gas can be performed in a short time. Further, the heater for the deposition layer 15 may be heated by incorporating a heater in the lid 3 or the lid 20.

FIG. 10 is a graph showing the results of investigation on the number of bubbles, the diameter of bubbles, and the expansion coefficient in the opaque layer of the quartz glass crucible manufactured by the manufacturing methods of the fourth and fifth embodiments. In this figure, the improved product 2 is the one according to the fourth embodiment, in which He gas is introduced after covering the lid 20 to evacuate to 5 Torr, and an arc is generated. The improved product 3 is according to the fifth embodiment, in which a He gas flow is generated in the deposition layer 15 at a vacuum of 160 Torr. The improved product 3 has a higher expansion coefficient than the improved product, but in the manufacture of the improved product 3, the expansion coefficient can be reduced by heating the deposition layer 15 with the halogen lamp or the like. In addition, it is needless to say that the expansion coefficient of the improved product 2 can be further reduced by heating the deposition layer 15 in advance.

As described above, according to the present embodiment, the removal of contaminants caused by external factors of the operating environment typified by the entrainment of the air and the further removal of impurities contained in the raw material powder are actively performed. Has been done. As a result, the amount of inert gas confined in the transparent layer of the quartz glass crucible was reduced to the utmost.

Although the present embodiment has been described with reference to the case in which H 2 is used as the introduced gas, the same
Introduced gases other than gas (O2, H2 O, He, and Ne)
), The number of bubbles, the diameter of bubbles, and the like were similarly improved, and good results were obtained for the single crystal yield.

Further, the gas supplied from the mold 1 in the third to fifth embodiments is not limited to He gas, but may be other rapid diffusion gas, for example, H 2, or He gas may be H 2 gas. May be mixed.

[0078]

As is apparent from the above description, according to the first to eighth aspects of the present invention, a gas such as O2 or H2 is injected into the arc to melt not only quartz powder in the spraying but also melting. Since high temperature acts on the layer to remove impurities in the quartz powder, it is possible to prevent bubbles caused by the impurities from entering the inner surface layer of the crucible. Also, even if
Even when air bubbles are mixed, the mixed air is mostly replaced by the introduced gas, so that a pressure reducing action in the air bubbles is expected. As a result, it is possible to provide a quartz glass crucible in which bubbles do not burst even under a high heat load, and a high yield can be expected even in pulling a large-diameter semiconductor single crystal.

Further, according to the ninth to sixteenth aspects of the present invention, since the voids in the deposited layer of quartz powder as a raw material are replaced with He gas, bubbles mixed into the opaque layer of the quartz glass crucible are prevented. The coefficient of expansion becomes small, and the thermal conductivity can be moderated when used at high temperatures. As a result, abnormal temperature rise of the quartz glass crucible can be avoided, and expansion and burst of bubbles in the transparent layer can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of an apparatus for manufacturing a quartz glass crucible according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a bubble diameter and a yield of a single crystal.

FIG. 3 is a diagram comparing bubbles before and after using a quartz glass crucible.

FIG. 4 is a diagram showing the relationship between the coefficient of expansion and the yield of single crystallization.

FIG. 5 is a cross-sectional view of a main part showing a manufacturing apparatus of a quartz glass crucible according to a second embodiment.

FIG. 6 is a cross-sectional view illustrating a main part of a manufacturing apparatus of a quartz glass crucible according to a third embodiment.

FIG. 7 is a diagram comparing air bubbles before and after using an opaque layer of a quartz glass crucible.

FIG. 8 is a cross-sectional view illustrating a main part of a quartz glass crucible manufacturing apparatus according to a fourth embodiment.

FIG. 9 is a cross-sectional view illustrating a main part of an apparatus for manufacturing a quartz glass crucible according to a fifth embodiment.

FIG. 10 is a diagram comparing bubbles before and after using an opaque layer of the quartz glass crucible according to the fourth and fifth embodiments.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mold, 1B ... Cooling water pipe, 2 ... Rotating shaft, 3 ...
Heat shield plate, 4,5 graphite electrode, 6 gas nozzle, 7 quartz inlet tube, 6A H2 gas inlet, 8
... Hopper, 10 ... Bottom hole, 11 ... Top hole, 15 ...
Sedimentary layer, 16 ... side hole, 17, 23 ... switch, 1
8 Vacuum pump 19 Gas supply source 70A Inlet tube 70B O2 gas inlet

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyuki Watanabe 568, Tanaka, Kawamoto-machi, Osato-gun, Saitama Prefecture Kusunawa-Waquartz, Inc. Reference) 4G014 AH08 4G077 AA02 BA04 CF10 HA12 PD02

Claims (16)

[Claims] 1. A method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge between graphite electrodes in a rotating mold and a crucible is formed, wherein H2, O2, H2O, He, and Ne gases are filled in the mold. Supplying a quartz powder to the inner surface of the mold by passing at least one of the gases through an atmosphere of the supplied gas. 2. A method of manufacturing a quartz glass crucible in which a quartz powder is melted by an arc discharge between graphite electrodes in a rotating mold to form a crucible, and wherein H2 gas and O2 gas are supplied into the mold. Supplying quartz powder to the inner surface of the mold by passing the gas through the atmosphere of the gas. 3. The quartz powder is sprayed into the mold so that the quartz powder is softened in an arc discharge atmosphere before reaching the inner surface of the mold. 3. The method for producing a quartz glass crucible according to 2. 4. The gas and quartz powder are supplied through a double cylinder, and one of the quartz powder and the gas is supplied from an inner cylinder of the double cylinder, and the quartz powder and the gas are supplied from an outer cylinder. The method for producing a quartz glass crucible according to claim 1, wherein the other is supplied. 5. The gas and the quartz powder are supplied through a double cylinder. The quartz powder is supplied from an inner cylinder of the double cylinder, and the gas is supplied from an outer cylinder whose tip projects beyond the inner cylinder. The method for producing a quartz glass crucible according to claim 1, wherein the quartz glass crucible is supplied. 6. The gas and quartz powder are supplied through a double cylinder, wherein the quartz powder is supplied together with O2 gas from an inner cylinder of the double cylinder, and H2 gas is supplied from an outer cylinder. The method for producing a quartz glass crucible according to claim 2 or 3. 7. The method for manufacturing a quartz glass crucible according to claim 6, wherein the tip of the inner cylinder of the double cylinder is retracted from the tip of the outer cylinder. 8. The quartz glass according to claim 1, wherein at least quartz powder of the quartz powder and the gas is intermittently supplied while maintaining the arc discharge. Crucible manufacturing method. 9. A method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge in a rotating mold and a crucible is formed, wherein a deposition layer of quartz powder is formed along an inner surface of the mold; Supplying He and / or H2 gas to the deposition layer from a predetermined position between a side wall and a bottom of the deposition layer; supplying the He and / or H2 gas for a predetermined time; and then starting an arc discharge; Stopping the supply of the He and / or H2 gas and evacuating from the deposited layer when a thin film molten layer is formed on the surface of the substrate, and once the deposited layer reaches a predetermined degree of vacuum, Restarting the supply of the stopped He and / or H2 gas. 10. A method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge in a rotating mold and a crucible is formed, wherein a deposition layer of quartz powder is formed along an inner surface of the mold; After the layer is formed, the upper opening of the mold is covered, and the inside of the mold is evacuated. When a predetermined degree of vacuum is reached in the mold, He and / or H2 gas is introduced into the mold. And starting the arc discharge by opening the lid when the pressure in the mold rises to a predetermined value. After opening the lid, supply of the He and / or H2 gas is started. A method for manufacturing a quartz glass crucible, wherein the method is continued for a predetermined time. 11. A method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge in a rotating mold and a crucible is formed, wherein a deposition layer of quartz powder is formed along an inner surface of the mold; Supplying He and / or H2 gas to the deposition layer from a predetermined position between a side wall and a bottom of the deposition layer; supplying the He and / or H2 gas for a predetermined time; and then starting an arc discharge; And evacuation of the deposited layer from above the side wall of the mold while continuously supplying the He and / or H2 gas when a thin film melted layer is formed on the surface of the quartz glass crucible. Manufacturing method. 12. The supply position of the He and / or H2 gas when the thin film molten layer is formed is switched to an upper portion of the side wall of the mold, and the He and H2 gas are supplied to the He before the arc discharge.
12. The method for manufacturing a quartz glass crucible according to claim 11, wherein the deposition layer is evacuated from a position where the H2 gas is supplied. 13. A method for manufacturing a quartz glass crucible in which a quartz powder is melted by arc discharge in a rotating mold and a crucible is formed, wherein a deposition layer of quartz powder is formed along an inner surface of the mold; After the layer is formed, the upper opening of the mold is covered, and the inside of the mold is evacuated. When the inside of the mold reaches a predetermined degree of vacuum, a predetermined position between the side wall and the bottom of the mold. He into the mold from
And / or supplying H2 gas; and starting the arc discharge by opening the lid when the pressure in the mold rises to a predetermined value, and forming a thin film molten layer on the surface of the deposition layer. And evacuation of the deposited layer from above the side wall of the mold while continuously supplying the He and / or H2 gas. 14. The supply position of the He and / or H2 gas when the thin film molten layer is formed is switched to an upper portion of the side wall of the mold, and the He and / or H2 gas is supplied before the arc discharge.
14. The method for manufacturing a quartz glass crucible according to claim 13, wherein the deposition layer is evacuated from a position to which H2 gas has been supplied. 15. After melting the deposition layer for a predetermined time,
H2, O2, H2 O, He, and N
supplying at least one kind of gas from the group consisting of e gas; and supplying quartz powder to the inner surface of the mold by passing the gas through the atmosphere of the supplied gas. The method for producing a quartz glass crucible according to any one of claims 9 to 14. 16. The method according to claim 15, wherein before the quartz powder reaches the inner surface of the mold, the quartz powder is sprayed into the mold so as to be softened in the atmosphere of the arc discharge. A method for manufacturing a quartz glass crucible.