JP6220772B2 - Method for producing quartz glass crucible - Google Patents

Description

The present invention relates to a method for producing a quartz glass crucible , and more particularly to a method for producing a quartz glass crucible having a strength that does not easily cause collapse even in a high heat environment in pulling a silicon single crystal.

A quartz glass crucible used for pulling a silicon single crystal by the Czochralski method (CZ method) is generated from an electrode placed around the axis of the mold against a molded body made of quartz powder formed in a crucible shape in the mold. It is manufactured by heating and melting by arc discharge.
In particular, the quartz glass crucible is required to have high strength because it does not cause collapse even in a high temperature environment and it is necessary to continuously pull up the single crystal for a long time. ing.

  For example, Patent Document 1 discloses a manufacturing method that gives strength by crystallizing a part inside or outside a quartz glass crucible. Specifically, a crucible manufacturing technique is described in which a devitrification accelerator is attached to the surface of a crucible and crystallized (devitrified) during temperature rise (about 600 ° C.) when pulling up a silicon single crystal.

FIG. 2 shows a cross-sectional view of a crucible formed by the manufacturing method disclosed in Patent Document 1. The crucible 50 of FIG. 2 has a bottom wall 51 and a side wall 52, which have inner surfaces 53, 54 and outer surfaces 55, 56, respectively.
An inner coating 57 is formed on the inner surfaces 53 and 54, and an outer coating 58 is formed on the outer surface 56. The inner coating 57 and the outer coating 58 contain a devitrification accelerator.

  Thus, according to the crucible 50 in which a part of the inner surface side or the outer surface side is crystallized, it is difficult for the quartz glass crucible to fall down even in a high temperature environment during use, and the silicon single crystal is pulled up. Can be performed for a long time.

Japanese Patent No. 3054362

However, in order to crystallize a part of the inner surface side or the outer surface side of the quartz glass crucible, it is necessary to attach a devitrification accelerator to the surface, and in particular, devitrification is caused in the inner surface side crucible of the quartz glass crucible. When the accelerator is adhered, there has been a technical problem that the devitrification accelerator is mixed into the silicon melt, resulting in a decrease in the purity of the silicon melt.
Further, Patent Document 1 shows that barium having a small segregation coefficient is used as a devitrification accelerator to reduce mixing into a silicon single crystal, but not a little barium is mixed into the molten liquid, and silicon There has been a technical problem that silicon single crystal defects are generated by bonding with oxygen therein.

The present invention has been made under the circumstances as described above, and without using a devitrification accelerator, by promoting the crystallization of the quartz glass crucible, the collapse does not occur even in a high heat environment. There is provided a method for producing a quartz glass crucible that can perform stable pulling for a long time, further suppresses contamination of impurities into the pulled silicon single crystal, and suppresses defects in the silicon single crystal. For the purpose.

In addition, a method for producing a silica glass crucible according to the present invention, which has been made to solve the above problems, supplies quartz powder to a crucible mold and rotates the crucible mold around an axis to form a compact. In a method for manufacturing a silica glass crucible, including the step of melting the formed body by arc discharge and forming a quartz glass crucible, in the step of melting the formed body by arc discharge and forming a quartz glass crucible The silica glass layer on the inner surface of the molded body is irradiated with ultraviolet light with an ArF ultraviolet laser with an irradiance of 4.8 to 8 W / m ² , or with a KrF ultraviolet laser with an irradiance of 24 to 32 W / m ^2. irradiated, having a characteristic to performing the step of density to produce a 1 × 10 ¹⁶ spins / cm ³ or more paramagnetic defects in the silica glass layer .

Thus, by irradiating the silica glass layer on the inner surface of the molded body with ultraviolet rays having a specific wavelength with a specific intensity, the silica glass layer has a paramagnetic defect with a density of 1 × 10 ¹⁶ spins / cm ³ or more. A crucible can be manufactured.
This crucible having a paramagnetic defect with a density of 1 × 10 ¹⁶ spins / cm ³ or more can introduce crystal nuclei due to the paramagnetic defect and promote crystallization of the crucible. A crucible having a higher viscosity than that of the crucible can be obtained, and it can withstand long-time pulling with little deformation. Further, since a devitrification accelerator is not used as in the prior art, there is no problem that the devitrification accelerator is mixed into the silicon melt and the purity is lowered, and the occurrence of defects such as dislocations in crystal pulling can be suppressed. .
In the case ArF ultraviolet laser irradiance of less than 4.8W / ^{m 2,} when KrF ultraviolet laser irradiance of less than 24W / ^{m 2,} the density in the silica glass layer is 1 × ^{10 16} spins / cm ³ Since the above paramagnetic defect cannot be formed, it is not preferable. On the other hand, when the ArF ultraviolet laser has an irradiance exceeding 8 W / m ² , the silica glass is damaged when the KrF ultraviolet laser has an irradiance exceeding 32 W / m ² , which is not preferable.

Here, the ultraviolet irradiation is preferably performed in a reducing atmosphere at normal pressure or reduced pressure. A defect structure is generated by irradiating the silica glass layer with ultraviolet rays having a specific wavelength at a specific intensity. This defect structure is preferably irradiated with ultraviolet light in a reducing atmosphere because hydrogen is recombined as a modifying group at a site once cut in a reducing atmosphere and relaxed.
Further, in order to remove oxygen in the quartz raw material which is a raw material of the crucible, it is desirable to perform the ultraviolet irradiation under reduced pressure.

According to the present invention, by promoting the crystallization of the quartz glass crucible without using a devitrification accelerator, no collapse occurs even in a high heat environment, and stable pulling can be performed for a long time. In addition, it is possible to obtain a method for producing a quartz glass crucible that can suppress the contamination of impurities in the pulled silicon single crystal and suppress defects in the silicon single crystal.

FIG. 1 is a cross-sectional view showing a partial configuration of a manufacturing apparatus capable of performing the method for manufacturing a silica glass crucible according to the present invention. FIG. 2 is a cross-sectional view of a crucible manufactured by a conventional method for manufacturing a quartz glass crucible.

Hereinafter, an embodiment of a method for producing a silica glass crucible according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a partial configuration of a manufacturing apparatus in which a method for manufacturing a quartz glass crucible according to the present invention is implemented.

This quartz glass crucible manufacturing apparatus 1 (hereinafter referred to as a crucible manufacturing apparatus 1) includes a crucible molding die 10. The crucible molding die 10 has a holding body 3 rotatably supported on a rotary shaft 2 in a furnace body (not shown). The holding member 3 is provided with an inner member 5 through the ventilation portion 4, and a crucible is formed in the inner member 5.
That is, quartz raw material powder is supplied to the inner member 5 of the crucible mold 10 and the rotating shaft 2 is rotated so that the inner peripheral surface of the inner member 5 is solidified by centrifugal force and formed into a crucible molded body P. It has become so.

An air passage 2 a is formed inside the rotary shaft 2 and communicates with the air vent 4. A pressure reducing mechanism 6 is provided below the rotating shaft 2, and the pressure reducing mechanism 6 reduces the space of the ventilation path 2 a and the ventilation portion 4 to a predetermined pressure.
Further, a pair of arc discharge carbon electrodes 7 (electrodes) are provided above the crucible mold 10. These carbon electrodes 7 are arranged in a state in which a tip portion directed downward is inclined by a predetermined angle toward the central axis. These carbon electrodes 7 are used to heat and melt a molded body P made of quartz raw material powder.

Further, above the crucible mold 10, laser irradiation devices 11 and 12 for irradiating the inner surface of the melting crucible molded body P with an ultraviolet laser are arranged. These laser irradiation devices 11 and 12 can be moved up and down by a lifting mechanism (not shown), and are provided so that the irradiation direction can be freely changed.
The drive control of the pair of carbon electrodes 7, the laser irradiation devices 11 and 12, the rotation drive device of the rotating shaft 2, and the like is performed by a control unit 30 including a computer.

Here, as the ultraviolet laser emitted by the laser irradiation devices 11 and 12, an ArF ultraviolet laser or a KrF ultraviolet laser is used. The illuminance of the ultraviolet laser, if the ArF ultraviolet laser is preferably 4.8~8W / ^{m 2,} in the case of KrF ultraviolet laser is preferably 24~32W / ^{m 2.}
The irradiation time of the ultraviolet laser is preferably 1 to 10 minutes, and the irradiation start of the ultraviolet laser is started simultaneously with the start of arc discharge by the carbon electrode 7 and melting of the inner peripheral surface of the crucible. Is preferred.

By irradiating the crucible molding P with ultraviolet rays in this way, defects of a predetermined density are generated inside the silica glass layer, and crystal nuclei are introduced as a result.
In the case ArF ultraviolet laser irradiance of less than 4.8W / ^{m 2,} when KrF ultraviolet laser irradiance of less than 24W / ^{m 2,} the density in the silica glass layer is 1 × ^{10 16} spins / cm ³ Since the above paramagnetic defect cannot be formed, it is not preferable.
On the other hand, when the ArF ultraviolet laser has an irradiance exceeding 8 W / m ² , the silica glass itself is damaged when the KrF ultraviolet laser has an irradiance exceeding 32 W / m ² , which is not preferable.

Further, generation of defects due to ultraviolet laser irradiation will be described in more detail.
By irradiating the silica glass layer on the inner surface side of the crucible with ultraviolet rays, the energy density inside the glass layer is increased, the reaction of the following formula (1) occurs, and the network structure in the glass is cut. Silica glass has various defects such as an oxygen deficiency defect and an oxygen excess defect. Among the paramagnetic defects, NBOHC (non-bridging oxygen deficiency defect, ≡Si—O.) And E ′ center (≡ There is a defect structure called Si.
-Si-O-Si---Si. +-Si-O. (1)

In the generation process of these defect structures, there is a high possibility that paramagnetic defects are generated through multiphoton absorption rather than direct interband excitation of electrons by photon absorption. Further, as is clear from the equation (1), the E ′ center and NBOHC are generated by a series of reactions, and the concentration is established in a relationship of approximately 1: 1.
Furthermore, it is also closely related to the network structure produced in the process of producing silica glass, and a defect structure is generated by ultraviolet irradiation not only by the reaction shown by the formula (1) but also by the formulas (2) and (3).
-Si-Si---Si. +-Si. (2)
-Si-O-O-Si---Si-O. + -Si-O. (3)

These defect structures are unstable structures with a kind of high energy state, and take a crystal structure during the relaxation process and recombination.
The mechanism for generating this crystal structure will be described in more detail. Among the defects in silica glass, there is 7.6 eV as a light absorption band. Peroxy radicals (POR, —Si—O—O) and NBOHC that are oxygen-rich defects can be attributed to this absorption band. The -Si-Si- structure also has an absorption band of 7.6 eV. This absorption band of 7.6 eV is known to have temperature dependence, takes a minimum at 800 ° C., and then recovers as the temperature rises. When the defect attributed to the absorption band is considered as -Si-Si-, this is the reaction of the formula (4). The meaning of having a minimum at 800 ° C. is that formula (4) is a reversible reaction, and at 800 ° C., ESi center —Si · is easily generated with a change in temperature and can be interpreted as further recovering. When defects such as E ′ center are generated in advance by irradiation, it is presumed that −Si · defects change to —Si—Si— due to structural change simply at 800 ° C. or higher.
-Si ・ + ・ Si- → -Si-Si- (4)

Since the structural change of silica glass causes a local structural change of the network, not a reaction between single molecules, the surrounding structural change is also promoted and crystal nuclei can be introduced with a certain probability. If the defect concentration is higher, crystal nuclei can be introduced at a constant rate even at a lower temperature. Crystal nuclei tend to viscously flow in the network structure in the quartz glass at high temperatures during use of the quartz crucible, promote the growth of the nucleus, and can achieve crystallization of the crucible itself in a short time.
As the defect structure is known to be a relaxation model in which hydrogen is recombined as a modifying group in a hydrogen atmosphere once cut in a hydrogen atmosphere, the crucible must be melted and irradiated with ultraviolet light in a reducing atmosphere that does not contain hydrogen. Is desirable.

Next, a process for manufacturing a quartz glass crucible in the quartz glass crucible manufacturing apparatus 1 configured as described above will be described.
First, the control unit 30 operates a rotary drive device (not shown) to rotate the crucible molding die 10 on the rotary shaft 2 at a high speed in the direction of the arrow, while supplying quartz raw material powder from a raw material powder supply device (not shown). Supply to the mold 10.

  When the quartz raw material powder is charged into the rotated crucible molding die 10, first, for example, coarse natural quartz glass raw material powder is charged, and further, for example, fine synthetic silica raw material powder is charged on the inner surface thereof. . The natural quartz glass raw material powder supplied into the crucible molding die 10 is pressed against the inner member 5 of the crucible molding die 10 by centrifugal force to form one layer.

  Following this natural quartz glass raw material powder, synthetic silica raw material powder is supplied into the crucible molding die 10, and the synthetic silica raw material powder is pressed against the natural quartz glass raw material powder layer by centrifugal force to form one layer, A crucible-shaped two-layer quartz filling layer (referred to as a crucible molded body P) is formed as a whole.

Thereafter, the inside of the furnace is made a reducing atmosphere containing a vacuum and a rare gas under the control of the control unit 30. The carbon electrode 7 is energized and heated from the inside of the crucible molded body P and melted sequentially from the inside of the molded body P substantially simultaneously with the pressure reduction by the operation of the pressure reducing mechanism 6.
Here, under the control of the control unit 30, ultraviolet laser irradiation is performed from the laser irradiation devices 11, 12 to the inner surface of the body and bottom of the crucible molded body P in accordance with the melting timing. The laser illuminance to be irradiated is 4.8 to 8 W / m ² in the case of ArF ultraviolet laser, and is in the range of 24 to 32 W / m ^{2 in} the case of KrF ultraviolet laser.
Paramagnetic defects are formed in the silica glass layer on the inner surface side of the crucible by ultraviolet irradiation during melting of the crucible molded body P.
Then, after melting the crucible molded body P, the quartz glass crucible in which the silica glass layer having paramagnetic defects on the inner surface side is formed as described above is obtained.

Further, when a silicon single crystal is pulled using the quartz glass crucible thus obtained, crystal nuclei are formed due to the paramagnetic defects during the temperature rise of the pulling, and crystal growth is induced to cause the crucible. Crystallization can be promoted.
In addition, the crystallized crucible has a higher viscosity than the amorphous quartz crucible, and therefore can be used for pulling a single crystal for a long time with little deformation. The reaction between the surface of the crystallized crucible and the silicon melt is mainly known for the etching phenomenon, but the crystallized crucible has a slower etching rate than the amorphous crucible. Therefore, the amount of dissolved oxygen in silicon can be reduced.

As described above, according to the embodiment of the present invention, silica having a specific density of paramagnetic defects is preferably obtained by irradiating the inner surface with ultraviolet rays having a specific illuminance during melting of the crucible molded body P. A quartz glass crucible in which a glass layer is formed can be obtained.
Then, by pulling up the silicon single crystal using the obtained quartz glass crucible, crystal nuclei caused by the paramagnetic defects can be introduced, and crystallization of the crucible can be promoted. As a result, it is possible to obtain a crucible having a higher viscosity than that of an amorphous quartz crucible, and it can withstand pulling for a long time with little deformation.
Further, since a devitrification accelerator is not used as in the prior art, there is no problem that the devitrification accelerator is mixed into the silicon melt and the purity is lowered, and the occurrence of defects such as dislocations in crystal pulling can be suppressed. .

In the embodiment, the ultraviolet laser is irradiated simultaneously with the melting of the crucible molded body P by arc discharge. However, the present invention is not limited to this.
For example, you may make it irradiate an ultraviolet laser after the heat-melting process by arc discharge (after melting of a crucible molded object, before cooling).

The manufacturing method of the quartz glass crucible according to the present invention will be further described based on examples. In this example, a quartz glass crucible was manufactured using the quartz glass crucible manufacturing apparatus described in the above embodiment, and verification was performed based on the obtained quartz glass crucible.

[Example 1]
In Example 1, a quartz glass crucible manufacturing apparatus was used in which a raw material quartz powder was put into a rotatable hollow mold and layered, and this was melted by a heating electrode.
Under a reduced pressure of 10 ⁴ Pa and in a reducing atmosphere of helium, melting by arc discharge from the carbon electrode was performed for 15 minutes.
Further, at the same time as melting the crucible compact, the inner surface of the crucible was irradiated with an irradiance of 24 W / m ² for 5 minutes using a KrF ultraviolet laser.
In addition, it is known that an arc discharge with a carbon electrode usually generates ultraviolet rays. In the case of the quartz glass crucible manufacturing apparatus, as a result of measurement with an ultraviolet intensity meter, the wavelength is 350 to 400 nm and the illuminance is 1.5 W. / M ² .

The crucible compact was cooled after melting, and the paramagnetic defect density inside the obtained quartz glass crucible was evaluated by an electron spin resonance apparatus (ESR). The defect density was 1 × 10 ¹⁷ spins / cm ³ . . When the density of the defect structure called E ′ center was evaluated, it was 4 × 10 ¹⁶ spins / cm ³ . Moreover, when the density of the defect structure called NBOHC was evaluated, it was 5 × 10 ¹⁶ spins / cm ³ .
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, the number of deformed crucibles was one, and it was possible to stably pull up the silicon single crystal for a long time. Moreover, when the inner surface of the crucible after the completion of the pulling was confirmed, it was confirmed that the ultraviolet irradiation portion was crystallized.

[Example 2]
A crucible was produced under the same conditions as in Example 1, and the inner surface of the crucible was irradiated under the same conditions as in Example 1 except that the illuminance of the KrF ultraviolet laser was similarly changed to 32 W / m ² .
As a result, when the paramagnetic defect density inside the obtained quartz glass crucible was evaluated by an electron spin resonance apparatus (ESR), the defect density was 1 × 10 ¹⁷ spins / cm ³ . When the defect density called E ′ center was evaluated, it was 4 × 10 ¹⁶ spins / cm ³ .
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, the number of deformed crucibles was one, and it was possible to stably pull up the silicon single crystal for a long time. Moreover, when the inner surface of the crucible after the completion of the pulling was confirmed, it was confirmed that the ultraviolet irradiation portion was crystallized.

[Comparative Example 1]
In Comparative Example 1, as in Examples 1 and 2, a quartz glass crucible manufacturing apparatus was used in which raw material quartz powder was put into a rotatable hollow mold and layered, and this was melted by a heating electrode.
Melting by arc discharge from a carbon electrode was performed for 30 minutes under a reduced pressure of 10 ⁴ Pa and a reducing atmosphere of helium.
As described in Example 1, it is known that when arc discharge is performed by a carbon electrode, ultraviolet rays are generated. In the case of the quartz glass crucible manufacturing apparatus, the wavelength is 350 to 350 as a result of measurement with an ultraviolet intensity meter. 400 nm, illuminance is 1.5 W / m ² .

The crucible compact was cooled after melting to obtain a quartz glass crucible. The obtained quartz glass crucible had a paramagnetic defect density of 5 × 10 ¹⁵ spins / cm ³ . When the ODC defect density was evaluated, it was 2 × 10 ¹⁵ spins / cm ³ .
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, there were four deformed crucibles, and the silicon single crystal could not be pulled stably for a long time.

[Comparative Example 2]
A crucible was manufactured under the same conditions as in Example 1, and the inner surface of the crucible was irradiated under the same conditions as in Example 1 except that the illuminance of the KrF ultraviolet laser was changed to 20 W / m ² .
The paramagnetic defect density of the obtained quartz glass crucible was 1 × 10 ¹⁴ spins / cm ³ or less. When the ODC defect density was evaluated, it was 1 × 10 ¹⁴ spins / cm ³ or less.
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, there were four deformed crucibles, and the silicon single crystal could not be pulled stably for a long time.

[Comparative Example 3]
A crucible was produced under the same conditions as in Example 1, and the inner surface of the crucible was irradiated under the same conditions as in Example 1 except that the illuminance of the KrF ultraviolet laser was similarly changed to 35 W / m ² .
As a result, local cracks were found in the quartz crucible, which proved unsuitable for use.

[Example 3]
In Example 3, as in Example 1, a quartz glass crucible manufacturing apparatus was used in which raw material quartz powder was put into a rotatable hollow mold and layered and melted by a heating electrode.
Melting by arc discharge from a carbon electrode was performed for 30 minutes under a reduced pressure of 10 ⁴ Pa and a reducing atmosphere of helium.
Further, at the same time as melting the crucible compact, the inner surface of the crucible was irradiated with an irradiance of 4.8 W / m ² for 2 minutes using an ArF ultraviolet laser.
In addition, it is known that an arc discharge with a carbon electrode usually generates ultraviolet rays. In the case of the quartz glass crucible manufacturing apparatus, as a result of measurement with an ultraviolet intensity meter, the wavelength is 350 to 400 nm and the illuminance is 1.5 W. / M ² .

The crucible compact was cooled after melting, and the paramagnetic defect density inside the resulting quartz glass crucible was evaluated by an electron spin resonance apparatus (ESR). The defect density was 6 × 10 ¹⁷ spins / cm ³ . . When the defect density called E ′ center was evaluated, it was 3 × 10 ¹⁷ spins / cm ³ .
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, the number of deformed crucibles was one, and it was possible to stably pull up the silicon single crystal for a long time. Moreover, when the inner surface of the crucible after the completion of the pulling was confirmed, it was confirmed that the ultraviolet irradiation portion was crystallized.

[Example 4]
A crucible was manufactured under the same conditions as in Example 3, and the inner surface of the crucible was irradiated under the same conditions as in Example 2 except that the illuminance of the ArF ultraviolet laser was similarly changed to 8 W / m ² .
As a result, when the paramagnetic defect density inside the obtained quartz glass crucible was evaluated by an electron spin resonance apparatus (ESR), the defect density was 2 × 10 ¹⁸ spins / cm ³ . When the defect density called E ′ center was evaluated, it was 1 × 10 ¹⁷ spins / cm ³ .
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, the number of deformed crucibles was one, and it was possible to stably pull up the silicon single crystal for a long time. Moreover, when the inner surface of the crucible after the completion of the pulling was confirmed, it was confirmed that the ultraviolet irradiation portion was crystallized.

[Comparative Example 4]
A crucible was manufactured under the same conditions as in Example 3, and the inner surface of the crucible was irradiated under the same conditions as in Example 1 except that the illuminance of the ArF ultraviolet laser was changed to 4.6 W / m ² .
As a result, when the paramagnetic defect density inside the obtained quartz glass crucible was evaluated by an electron spin resonance apparatus (ESR), the defect density was 7 × 10 ¹⁵ spins / cm ³ . When the defect density called E ′ center was evaluated, it was 3 × 10 ¹⁵ spins / cm ³ or less.
Further, ten of the obtained quartz glass crucibles were used to pull up a silicon single crystal for an 8-inch wafer 10 times.
As a result, there were four deformed crucibles, and the silicon single crystal could not be pulled stably for a long time.

[Comparative Example 5]
A crucible was manufactured under the same conditions as in Example 3, and the inner surface of the crucible was irradiated under the same conditions as in Example 1 except that the illuminance of the ArF ultraviolet laser was changed to 8.5 W / m ² .
As a result, local cracks were found in the quartz crucible, which proved unsuitable for use.

[Example 5]
Under the same conditions as in Example 1, the inner surface of the crucible was irradiated with a KrF ultraviolet laser at an illuminance of 24 W / m ² for various irradiation times. The crucible compact was cooled after melting to produce quartz glass crucibles having different paramagnetic defect densities. Then, using 10 obtained quartz glass crucibles, the silicon single crystal for 8-inch wafer was pulled up 10 times.
As a result, when the paramagnetic defect density of crucibles having three or less deformed crucibles (a smaller number than that of Comparative Example 1) was evaluated with an electron spin resonance apparatus (ESR), the defect density was 6 × 10 ¹⁶ spins / cm. ^Three or more crucibles.

[Example 6]
Under the same conditions as in Example 1, the inner surface of the crucible was irradiated with an ArF ultraviolet laser at an illuminance of 4.8 W / m ² for various irradiation times. The crucible compact was cooled after melting to produce quartz glass crucibles having different paramagnetic defect densities. Then, using 10 obtained quartz glass crucibles, the silicon single crystal for 8-inch wafer was pulled up 10 times.
As a result, when the paramagnetic defect density of crucibles having three or less deformed crucibles (a smaller number than that of Comparative Example 1) was evaluated with an electron spin resonance apparatus (ESR), the defect density was 6 × 10 ¹⁶ spins / cm. ^Three or more crucibles.

From the results of the above examples, the use of a quartz glass crucible having a density of the paramagnetic defect of 1 × 10 ¹⁶ spins / cm ³ or more enables stable pulling of the silicon single crystal for a long time. It was confirmed.
Further, in the step of melting the molded body by arc discharge to form a quartz glass crucible, an ArF ultraviolet laser is irradiated with ultraviolet rays at an irradiance of 4.8 to 8 W / m ^{2 on} the silica glass layer on the inner surface of the molded body. Irradiation or irradiation of ultraviolet rays with a irradiance of 24 to 32 W / m ² with a KrF ultraviolet laser generates paramagnetic defects with a density of 1 × 10 ¹⁶ spins / cm ³ or more in the silica glass layer. Confirmed.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of quartz glass crucible 2 Rotating shaft 2a Ventilation path 3 Holding body 4 Ventilation part 5 Inner member 7 Carbon electrode 10 Mold for crucible molding 11 Laser irradiation apparatus 12 Laser irradiation apparatus 30 Control part P Crucible molding

Claims (2)

A method comprising: supplying quartz powder to a crucible mold; rotating the crucible mold around an axis to form a molded body; and melting the molded body by arc discharge to form a quartz glass crucible. In the method for producing a glass crucible,
In the step of melting the molded body by the arc discharge to form a quartz glass crucible, the silica glass layer on the inner surface of the molded body is irradiated with ultraviolet light at an irradiance of 4.8 to 8 W / m 2 with an ArF ultraviolet laser. Or a step of generating a paramagnetic defect having a density of 1 × 10 16 spins / cm ³ or more in the silica glass layer by irradiating a KrF ultraviolet laser with ultraviolet rays at an irradiance of 24 to 32 W / m ^2. A method for producing a quartz glass crucible. 2. The method for producing a quartz glass crucible according to claim 1 , wherein the ultraviolet irradiation is performed in a reducing atmosphere at normal pressure or reduced pressure.

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