JP5226754B2 - Manufacturing method of large diameter quartz glass crucible for pulling silicon single crystal - Google Patents

Description

  The present invention relates to a method for producing a large-diameter quartz glass crucible used for pulling a silicon single crystal.

  Conventionally, a so-called Czochralski method has been widely used for manufacturing a single crystal material such as a single crystal semiconductor material. In this method, polycrystalline silicon is melted in a container, and the end portion of the seed crystal is immersed in the molten bath and pulled up while rotating, so that a single crystal having the same crystal orientation grows on the seed crystal. A quartz glass crucible is generally used for the single crystal pulling container.

  When polysilicon is melted in a quartz glass crucible and the silicon single crystal is pulled up, a periodic vibration wavefront is generated on the surface of the silicon melt, the silicon seed crystal cannot be bonded to the silicon melt, or the crystallinity of the silicon single crystal is disturbed. The problem is a common phenomenon.

  As one of the causes, when the heating energy supplied at the time of pulling is large or the degree of vacuum in the pulling chamber is large, the reaction at the contact portion between the quartz glass surface and the upper surface of the silicon melt liquid is activated, and the generation of SiO gas occurs. It is considered that the silicon melt liquid is likely to be repelled from the quartz glass surface, the molten metal surface vibration is strongly generated, and the state at the center of the silicon melt liquid becomes unstable.

  In particular, as the silicon single crystal becomes 8 ″ or more and the quartz glass crucible becomes larger in diameter in recent years, the heating energy and the degree of pressure reduction tend to increase, and the problem of molten metal vibration has become important.

  As a means for solving the above phenomenon, a method for improving the wettability of the inner surface of the quartz glass crucible to the silicon melt is conceivable. The wettability can be defined by the surface tension (surface free energy) of the inner surface of the quartz glass crucible, but there are several factors that affect the surface tension.

  Factors of the quartz glass crucible that determine wettability include the OH concentration, metal impurity concentration, and surface roughness of the inner surface. The OH group present on the inner surface is exposed on the glass surface, and readily decouples H + and has a negative polarity, and reversibly binds to Si +. The more this reaction is, the better the adhesion between the inner surface of the quartz glass crucible and the silicon melt.

  Next, as a factor that exerts the same effect as the OH group, there is a metal impurity on the inner surface of the quartz glass crucible. Metal impurities jump out from the inner surface of the quartz glass crucible in the form of + ions, the inner surface of the quartz glass crucible has a negative polarity, and the inner surface of the silicon melt and the quartz glass crucible is improved by the same mechanism as the OH group. It comes to adhere.

  In addition, if the surface roughness of the inner surface of the quartz glass crucible is large, the inner surface area increases, and the exposed OH groups and metal impurities jump out. Due to the above mechanism, the silicon melt and the inner surface of the quartz glass crucible have a strong adhesive force. Will have.

  The present invention has been made in view of the above circumstances, and by creating wettability on the inner surface of the quartz glass crucible, when the silicon single crystal is pulled up using this quartz glass crucible, the surface vibration of the silicon melt is suppressed. It is an object of the present invention to provide a method for producing a large-diameter quartz glass crucible for pulling up a silicon single crystal.

In order to solve the above-mentioned problems, a method for producing a quartz glass crucible according to the present invention uses a rotating upper opening mold to form a translucent quartz glass layer crucible base and a transparent formed on the inner wall surface of the crucible base. A method for producing a quartz glass crucible for pulling a silicon single crystal comprising a quartz glass layer, comprising: (a) supplying silicon dioxide powder into the mold and forming a preform along the inner surface of the mold; (B) a step of forming the semi-transparent quartz glass crucible base by heating and melting the preform, and (c) silicon dioxide in a high-temperature gas atmosphere in the crucible base during or after the formation of the crucible base. The process consists of supplying powder and scattering and fusing towards the inner wall surface to form a transparent quartz glass layer. When the quartz glass crucible is filled with polysilicon from the upper end of the produced quartz glass crucible and melted The inner surface of the quartz glass crucible by grinding the inner surface portion up to a position located below the molten metal surface of the silicon melt with a processing grinding means, dissolving with a dissolving liquid means, or sublimating with a heating means. Of a quartz glass crucible manufactured by adjusting the surface roughness of the glass so as to have a height difference of 10 to 50,000 nm in a distance of 4 μm and adjusting the absolute humidity of the melting and heating area in the crucible substrate. By adjusting the average OH concentration up to 1.0 mm in the depth direction of the surface to 100 to 500 ppm and adjusting the metal impurity concentration within 1 mm in the depth direction of the inner surface of the manufactured quartz glass crucible to 1 to 200 ppm The surface tension of the inner surface of the quartz glass crucible is set to 50 mN / m or less.

The method for producing a quartz glass crucible for pulling a silicon single crystal according to the present invention includes a quartz crystal crucible for pulling a silicon single crystal having a surface tension adjusted by adjusting the surface roughness of the inner surface of the quartz glass crucible using a rotating upper opening mold. This is a method for producing a glass crucible. Examples of the working grinding means include grinding with a diamond grindstone. As the solvent Kaieki means, and the like 20% HF solution. An example of the heating means is an oxyhydrogen burner. By this sublimation, the surface roughness of the inner surface of the quartz glass crucible can be adjusted by skipping SiO ₂ to leave the alumina portion.

  This large-diameter quartz glass crucible for pulling up a silicon single crystal is a quartz glass crucible for pulling up a silicon single crystal comprising a crucible base of a translucent quartz glass layer and a transparent quartz glass layer formed on the inner wall surface of the crucible base, The surface tension of the inner surface of the quartz glass crucible is 50 mN / m or less, and the surface tension value is set within a predetermined range by adjusting the surface roughness of the inner surface of the quartz glass crucible. It is characterized by. If this surface tension exceeds 50 mN / m, there is a disadvantage that the melt surface vibration of silicon melt always occurs. The surface roughness may be a height difference of 10 nm or more within a distance of 4 μm, but preferably a height difference of 20 to 50,000 nm.

  It is preferable to set the surface tension value within a predetermined range by adjusting the average OH concentration up to 1.0 mm in the depth direction of the inner surface of the quartz glass crucible. The average OH concentration may be 100 ppm or more, but is preferably 200 to 500 ppm.

  It is preferable to set the surface tension value within a predetermined range by adjusting the metal impurity concentration within 1 mm in the depth direction of the inner surface of the quartz glass crucible. The metal impurity concentration may be 1 ppm or more, but is preferably 10 to 200 ppm.

  It is preferable to set the surface tension value within a predetermined range by adjusting the concentration of OH contained in the quartz glass raw material used within 1 mm in the depth direction of the inner surface of the quartz glass crucible. The OH concentration may be 20 ppm or more, but is preferably 100 to 500 ppm.

It is preferable that the value of the surface tension is set within a predetermined range by adjusting the specific surface area of the quartz glass raw material used in a depth range within 1 mm of the inner surface of the quartz glass crucible. The specific surface area is preferably, 1.0~100m ² / 100g.

Another aspect of the method for producing a quartz glass crucible for pulling a silicon single crystal is to adjust the average OH concentration up to 1.0 mm in the depth direction of the inner surface of the quartz glass crucible using a rotating upper opening mold. a method for producing a silicon single crystal for pulling up the quartz glass crucible was adjusted tension, (a) by supplying the silicon dioxide powder in the mold to form a pre-molded body along the mold inner surface, ( b) by heating and melting the front molded body to form a translucent quartz glass crucible base body (c), after the formation of or forms the crucible base body, the silicon dioxide powder into the hot gas atmosphere in the crucible base body Is produced by adjusting the absolute humidity of the melting and heating area in the crucible substrate, and forming a transparent quartz glass layer by scattering and fusing toward the inner wall surface. Adjust the average OH concentration in the depth direction 1.0mm of the inner surface of the glass crucible, and sets the value of the surface tension of the quartz glass crucible in a predetermined range.

  The inner surface portion from the upper end of the quartz glass crucible to the position located below the melt surface of the silicon melt when the quartz glass crucible is filled and melted varies depending on the amount of silicon melt. For example, it is sufficient to make it 70% of the total height from the upper end of the quartz glass crucible, preferably 50%. If the surface roughness of the inner surface portion of the quartz glass crucible is too wide, there is a disadvantage that the surface deterioration accompanying the pulling operation of the silicon single crystal easily proceeds.

  As described above, according to the present invention, by creating wettability on the inner surface of the quartz glass crucible, the surface vibration of the silicon melt liquid surface is suppressed when the silicon single crystal is pulled up using the quartz glass crucible. The effect that it can be achieved is achieved.

It is a schematic sectional explanatory drawing which shows the apparatus used for implementation of the method of this invention, and the manufacturing method of the quartz glass crucible which uses this apparatus. It is a partial cross section figure of the quartz glass crucible for silicon single crystal pulling obtained by the method of the present invention.

  In the following, one embodiment of the present invention will be described with reference to the accompanying drawings. However, it is needless to say that these descriptions are given by way of example and should not be construed as limiting.

  FIG. 1 is an explanatory sectional view showing an apparatus used for carrying out the method of the present invention and a method for producing a quartz glass crucible using the apparatus. FIG. 2 is a partial cross-sectional view of a quartz glass crucible for pulling a silicon single crystal obtained by the method of the present invention.

  In FIG. 1, the rotary mold 1 includes a rotary shaft 2. A cavity 1a is formed in the mold 1, and a base 3 of a translucent quartz glass made of silicon dioxide powder, for example, natural quartz powder, that is, a quartz glass crucible constituting an outer layer is disposed in the mold cavity 1a.

  The base 3 is charged with silicon dioxide powder into a rotating mold 1 and formed along the inner wall of the mold 1 to form a required crucible-shaped preform, and this preform is heated from the inner surface. It is manufactured by melting silicon dioxide powder and then cooling it.

  For heating from the inner surface, an arc discharge device 5 having carbon electrodes 51 and 52 connected to a power source 10 as shown in FIG. 1 can be used. A plasma discharge device may be used instead of the arc discharge device 5. The production of the substrate 3 is described in detail in Japanese Patent Publication No. 4-22861.

  The apparatus shown in FIG. 1 includes a quartz powder supply tank that stores synthetic quartz powder 6 above the mold 1 in order to form the inner layer 4. The supply tank 9 is connected to a discharge pipe 93 provided with a weighing feeder 92. A stirring blade 91 is disposed in the supply tank 9. The upper part of the mold is covered with a lid 71 leaving a slit opening 75.

  After the substrate 3 is formed or during the formation of the substrate 3, the weighing feeder 92 for supplying the synthetic quartz powder 6 is adjusted while heating by the discharge from the carbon electrodes 51 and 52 of the arc discharge device 5 is continued. Then, the synthetic quartz powder is supplied from the discharge pipe 93 into the base 3. By the operation of the arc discharge device 5, a high temperature gas atmosphere 8 is formed in the base 3. Therefore, the synthetic quartz powder is supplied into the high-temperature gas atmosphere 8.

  The high-temperature gas atmosphere refers to an atmosphere formed around the arc discharge using the carbon electrodes 51 and 52, and has a temperature sufficient to melt the quartz glass, that is, a high temperature of 2000 to several hundred degrees.

  The synthetic quartz powder supplied in the high temperature gas atmosphere 8 is melted at least partly by the heat in the high temperature gas atmosphere 8 and is simultaneously scattered toward the inner wall surface of the substrate 3, so that the synthetic quartz powder is applied to the inner wall surface of the substrate 3. A substantially bubble-free quartz glass layer, that is, the inner layer 4 is formed on the inner surface of the substrate 3 by being integrally fused with the substrate 3. The method for forming the inner layer 4 is described in detail in the above-mentioned Japanese Patent Publication No. 4-22861.

  FIG. 2 shows a cross section of a quartz glass crucible obtained by this method. The quartz glass crucible according to the present invention comprises an outer layer formed by heating and melting a silicon dioxide powder, for example, natural quartz powder, that is, a base 3 and a synthetic quartz powder released into a high-temperature gas atmosphere to be melted and scattered. 3 and the inner layer 4 formed by adhering to the inner wall surface.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples, and various modifications can be made without departing from the technical idea of the present invention. Of course.

( Experimental example 1)
In absolute humidity 25 g / m ³ or more melting area, a specific surface area of 10 m ^2/100 g, the natural quartz glass powder of particle size 500 microns 50 microns, in mold inner diameter 730mm rotating at 100 rpm 30 mm At the same time, a synthetic quartz glass powder having an OH concentration of 100 ppm is supplied from above at a rate of 100 g / min, and a transparent glass layer without bubbles is formed. It is formed with a thickness of 1 to 3 mm over the entire inner surface area. The fused quartz glass crucible after melting was taken out of the mold and the condition of the inner surface was measured for the measurement items shown in Tables 1 and 2, and the results are shown in Tables 1 and 2.

  In Table 2, AAS is Atomic Absorption Spectrometry, ICP-AES is Inductively Coupled Plasma Atomic Emission Spectroscopy, and ICP-MS is Inductively Coupled Plasma Plasma Mass Spectrophotometer ( Inductively Coupled Plasma Mass Spectrometer).

  The quartz glass crucible was filled with polysilicon and melted, and the silicon single crystal was pulled up. During the seeding of the silicon melt and the pulling of the silicon single crystal, vibration of the silicon melt was not confirmed (Table 3), and the pulling was completed stably.

(Example 1 )
A quartz glass crucible was prepared in the same procedure as in Experimental Example 1 using a synthetic quartz glass raw material having an OH concentration of 5 ppm used for forming the crucible inner transparent layer. Next, the inner surface of the quartz glass crucible from the upper end to 70% was washed with a 20% HF solution for 60 minutes. The properties of this quartz glass crucible were as shown in Table 3. Furthermore, the silicon single crystal was pulled up with this quartz glass crucible in the same manner as in Experimental Example 1, but there was no molten metal surface vibration (Table 3).

(Example 2 )
A quartz glass crucible was prepared in the same manner as in Experimental Example 1 using a synthetic quartz glass raw material used for forming a crucible inner transparent layer having an OH concentration of 5 ppm and a total metal impurity concentration of 20 ppm. Next, the inner surface of the portion of the quartz glass crucible from the upper end to 70% of the height was roughly cut by grinding with a diamond grindstone. The properties of this quartz glass crucible were as shown in Table 3. With this quartz glass crucible, the silicon single crystal was pulled up in the same manner as in Experimental Example 1, but there was no molten metal vibration (Table 3).

(Example 3 )
A quartz glass crucible was prepared in the same manner as in Experimental Example 1 using a natural quartz glass raw material having an OH concentration of 5 ppm used for forming a crucible inner surface transparent layer. Next, the inner surface of the portion from the upper end of the height of the quartz glass crucible to 70% was sublimated with an oxyhydrogen burner. The properties of this quartz glass crucible were as shown in Table 3. Using this quartz glass crucible, the silicon single crystal was pulled up in the same manner as in Experimental Example 1. During the seeding of the silicon melt and the pulling of the single crystal, the vibration of the silicon melt was not confirmed, and the pulling was finished stably (Table 3).

( Experimental example 2 )
The quartz glass crucible was the same as in Experimental Example 1 except that natural quartz glass powder having an OH concentration of 5 ppm and a total metal impurity concentration of 20 ppm was used as the quartz raw material powder used for forming the crucible inner transparent layer. It was created. The properties of this quartz glass crucible were as shown in Table 3. Using this quartz glass crucible, the silicon single crystal was pulled up in the same manner as in Experimental Example 1. During the seeding of the silicon melt and the pulling of the single crystal, the vibration of the silicon melt was not confirmed, and the pulling was finished stably (Table 3).

(Example 4 )
A quartz glass crucible was prepared in the same procedure as in Experimental Example 1, and the entire inner surface of the quartz glass crucible was washed with a 20% HF solution for 60 minutes. The properties of this quartz glass crucible were as shown in Table 3. Furthermore, the silicon single crystal was pulled up with this quartz glass crucible in the same manner as in Experimental Example 1, but there was no molten metal surface vibration (Table 3).

(Comparative Example 1)
A quartz glass crucible was prepared in the same manner as in Experimental Example 1 using a synthetic quartz glass raw material having an OH concentration of 5 ppm used for forming a crucible inner surface transparent layer. The properties of this quartz glass crucible were as shown in Table 3. Using this quartz glass crucible, the silicon single crystal was pulled up in the same manner as in Experimental Example 1. During the seeding of the silicon melt and the pulling of the single crystal, the vibration of the silicon melt was strongly confirmed, and the pulling was stopped halfway (Table 3).

  1: mold, 1a: cavity, 2: rotating shaft, 3: substrate, 4: inner layer, 5: arc discharge device, 6: synthetic quartz powder, 8: high-temperature gas atmosphere, 9: supply tank, 10: power supply, 51, 52: carbon electrode, 71: lid, 75: slit opening, 91: stirring blade, 92: metering feeder, 93: discharge pipe.

Claims (1)

This is a method for producing a quartz glass crucible for pulling a silicon single crystal comprising a crucible base of a translucent quartz glass layer and a transparent quartz glass layer formed on the inner wall surface of the crucible base using a rotating upper opening mold. And
(A) supplying silicon dioxide powder into the mold and forming a pre-molded body along the inner surface of the mold;
(B) a step of heating and melting the preform and forming a semitransparent quartz glass crucible base;
(C) comprising or forming a transparent quartz glass layer by supplying silicon dioxide powder into the high-temperature gas atmosphere in the crucible substrate and then fusing and melting toward the inner wall surface during or after the formation of the crucible substrate;
Grinding the inner surface part from the upper end of the manufactured quartz glass crucible to the position located below the molten metal surface of the silicon melt when the quartz glass crucible is filled with polysilicon and melted by means of processing grinding , melting The surface roughness of the inner surface of the quartz glass crucible is adjusted to have a height difference of 10 to 50,000 nm in a distance of 4 μm by dissolving with a liquid means or sublimating with a heating means , and Quartz glass produced by adjusting the average OH concentration up to 1.0 mm in the depth direction of the inner surface of the quartz glass crucible manufactured by adjusting the absolute humidity of the melting and heating area in the crucible substrate, and manufacturing the quartz glass By adjusting the metal impurity concentration within 1 mm in the depth direction of the inner surface of the crucible to 1 to 200 ppm, the surface tension of the inner surface of the quartz glass crucible Method for manufacturing a silica glass crucible and setting below 50 mN / m.

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