JPH1143394A - Production of quartz glass crucible for pulling up high-purity single crystal silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a crucible hardly crystallizable even at the time of use at high temperatures by treating a raw material quartz sand with hydrogen chloride gas and/or chlorine gas at a specific temperature or above and regulating the respective contents of Na and K to specific values or below. SOLUTION: A raw material quartz sand is treated with a gas at a temperature of >=1,300 deg.C to regulate the respective contents of Na and K to <=50 ppb. A brown mark found after completing the pulling up is an oxygen deficient cristobalite which is reduced and recombined. Since the planar devitrification is lost by dissolution at high temperatures with time, the deterioration in decontamination factor(DF) ratio is hardly caused. The three-dimensional devitrification is a problem and the cristobalite is peeled and mixed in the silicon melt to cause the formation of polycrystals. This is because the Na and K bind to uncross-linked oxygen through ionic bonds to promote the recombination. A purifying apparatus 1 is a carbon cylinder and a baking furnace, having a heater 2 formed on the outer periphery thereof and rotated by an additionally installed motor M for rotation. Numeral 6 is a hydrogen chloride gas source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass crucible used for pulling a silicon single crystal used for a semiconductor or the like from molten silicon.

[0002]

2. Description of the Related Art As a tendency of pulling single crystal silicon,
Recently, multi-pulling has been performed to reduce costs. In other words, one quartz crucible was used for one pull, but an attempt was made to increase the number of times the quartz crucible was used in order to reduce costs, and two to three single crystal silicon ingots were pulled with the same crucible. Have been tried.

[0003] In addition, since the diameter has been shifted to a large diameter, the heat load is large due to the heavy charge of the polycrystalline silicon,
And it is in the direction of longer time. Under such use conditions, the quartz glass is often softened, devitrified, or ruptured in bubbles. Thus, when glass and cristobalite are mixed in the silicon melt, the silicon single crystal is disturbed, and the yield is reduced.

[0004] In order to solve this problem, there is disclosed a technique of forming a transparent layer on the inner surface of a crucible in direct contact with a silicon melt (Japanese Patent Publication No. 4-22861). In addition, a technique has been disclosed in which a similar degree of vitrification of the inner surface layer is improved so that it is difficult to crystallize (Japanese Patent Publication No. 6-560).
No. 6). In addition, there is a technique in which the crucible is electrolyzed to reduce alkalinity (Japanese Patent Publication No. 64-6158).
The removal of the contaminant layer by etching of about m is disclosed in JP-A-63-166793.

[0005]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies on quartz crucibles having a good DF conversion rate. As a result, when the surface of quartz crucible contains impurities of Na and K, they are exposed to a high temperature when pulling a silicon single crystal. Discovered that the glass was transformed into β-cristobalite, which exfoliated and melted into the silicon melt, lowering the yield of single crystal silicon. Furthermore, it was found that this phenomenon was extremely dependent on the purity of the inner surface.

Based on the above findings, a method of removing impurities of Na and K from the surface of a quartz glass crucible was examined, and as a result, a method of producing a crucible that is difficult to crystallize even at a high temperature was developed.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a quartz glass crucible, wherein Na and K are each reduced to 50 ppb or less by treating raw quartz sand with hydrogen chloride gas and / or chlorine gas at 1300 ° C. or more. A method for producing a high-purity quartz crucible characterized by producing a crucible for pulling single-crystal silicon from the raw material quartz sand by a rotary molding method, and by using this crucible, it is possible to obtain single-crystal silicon in a high yield. The point is that you can do it.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The quality of single crystal silicon is deeply related to the characteristics of a quartz glass crucible because the quartz glass crucible is in direct contact with the silicon single crystal at the interface.
Conventionally, it has been known that foreign matters adhere to the edges of the single crystal and become polycrystalline except for troubles in the single crystal pulling apparatus. It has been found that cristobalite is mixed into the silicon melt and adheres to the edge of the silicon single crystal to be polycrystallized, whereby the pulling of the single crystal silicon is interrupted, and the DF conversion rate is reduced.

The brown ring seen after the completion of the pulling is called a brown mark. This ring is an oxygen-deficient cristobalite, which is reduced by a reaction with molten silicon, recombined and transferred to cristobalite.

The planar devitrification seems to spread and become larger with the passage of time due to the equilibrium relationship with the erosion. However, in the case of a planar brown mark, β-cristobalite hardly peels off from the surface, and is melted with time at a high temperature.

The problem is three-dimensional devitrification, and the crystal first has crystal nuclei, which grow three-dimensionally and become large. Since cristobalite has physical properties different from quartz glass, it is exfoliated and mixed into the silicon melt. Then, it stochastically adheres to the crystal edge and causes poly-crystallization. The cause of the three-dimensional devitrification is largely due to impurities contained in the quartz glass. In particular, alkali metals move three-dimensionally in quartz glass. Na and K are ionically bonded to non-crosslinked oxygen, which are easily broken at high temperatures and promote recombination.

The present inventors first paid attention to the fact that quartzite and quartz sand are usually obtained only in the form of quartz. Impurities, particularly problematic Na and K, have a large ionic radius and cannot fit into the crystal skeleton of quartz, and exist separately from quartz, for example, as feldspar or mica. As a method for this removal, it is common practice to separate quartz and mica from the crushed material and carry out flotation. However, when the flotation is completely performed and the quartz particle surface is further etched with hydrofluoric acid aqueous solution,
It was difficult to reduce a and K to 0.5 ppm or less.

Therefore, the present inventors have prepared various kinds of quartz sands.
When treated with hydrogen chloride gas and / or chlorine gas at 00 ° C or more, Na and K may be 50 ppb depending on the conditions.
It has been found that:

The principle will be briefly described.
a and K react with hydrogen chloride gas and / or chlorine gas to form chloride. The boiling point of chloride is 1413 ℃ in Nacl, Kcl
Has a melting point of 800.4 ° C., Kc
Since it is 776 ° C. in l, it is separated from the raw material powder in relation to the corresponding vapor pressure.

The reason why the treatment temperature is set to 1300 ° C. or higher is that, in the case of ordinary quartz sand, in order to reduce Na and K to 50 ppb or less, it is necessary to convert the extreme surface of quartz particles into cristobalite. is there. However, 1500 ° C
In this case, since the quartz particles cannot maintain their original particle diameters, including sintering, 1300 to 1500 ° C. is most desirable.

The reason why Na and K are set to 50 ppb or less is that when a silicon single crystal is actually pulled up using this crucible, the yield, that is, the DF conversion rate is N
This is because a and K are dramatically improved after 50 ppb.

In particular, a target of 10 "in a 22" crucible
This is because 100% yield can be achieved in a zero-hour operation (2 Ingots).

Hereinafter, examples and comparative examples will be described. FIG. 1 shows an apparatus used for purifying the raw material quartz used in Examples and Comparative Examples. FIG. 1 is a schematic explanatory view of a purification apparatus, in which 1 is a carbon cylinder, which is a firing furnace formed with a heater 2 on its outer peripheral surface and rotated by an attached rotation motor M. The carbon cylinder 1 is configured so as to be inclined from the raw material input port 4 side of the raw material input hopper 3 to the raw material outlet 5 side, and the raw material of the raw material input hopper 3 is input from the input port 4 and fired in the furnace while exiting. It is discharged outside from 5. Reference numeral 6 denotes a hydrogen chloride gas source. The hydrogen chloride gas is supplied into the furnace from a supply port 7, and exhaust gas is discharged to the outside from an exhaust port 8.

[0019]

[Example 1] IOTA-4 (product name and characteristics (purity of quartz sand) of silica powder manufactured by Unimine Co., USA) is supplied at 10 kg / H to the rotated carbon cylinder of FIG. Hydrogen gas was flowed at 10 l / min. The furnace temperature was 1400 ° C. The convection time was 30 minutes, and the recovered powder was float-fed with pine oil to remove carbon, and washed with a 5% aqueous solution of H202: NH40H = 2: 1. After drying, the purity was checked. Na,
K and Li were measured with a Zeeman atomic absorption spectrophotometer, and the other elements were measured with an ICP emission spectrophotometer. The results (purity of the treated sand) are shown in Table 2. SUS rotating this raw material sand
Put into a water-cooled mold and apply voltage to the arc electrode.
A 22 ″ quartz glass crucible was melted in minutes. The melt was taken out, the unmelted powder on the outer surface was removed with high-pressure water, and the height was adjusted to 400 mm with a diamond cutter. 30% aqueous solution
The inner surface was soaked by 4 μm. Next, the substrate was washed with ultrapure water and naturally dried in a class 1000 clean room. The results of the DF conversion ratio (yield when two or more 8 ″ were raised using the crucibles of the examples and the comparative examples) are shown in which the single crystal silicon ingot of 8 ″ was actually pulled up using the 22 ″ crucible. 3 is shown.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

Example 2 FIG. 1 shows H-8 Sand (trade names and characteristics (purity of quartz sand) of silica powder manufactured by Wacom Mining & Mining Co., Ltd.).
Was supplied at 10 kg / H, and hydrogen chloride gas was flowed at 10 l / min. The furnace temperature was 1300 ° C. The convection time was 30 minutes, and the recovered powder was floated with pine oil to remove carbon, and H202: NH40H =
Washed with a 2: 1 5% aqueous solution. After drying, the purity was checked. Na, K, and Li were measured with a Zeeman atomic absorption spectrophotometer, and the other elements were measured with an ICP emission spectrophotometer. Table 2 shows the results. This raw material sand is put into a rotating SUS water-cooled mold, a voltage is applied to the arc electrode, and 22 "is applied in 25 minutes.
Was melted. The melt was taken out, unmelted powder on the outer surface was removed with high-pressure water, and the height was adjusted to 400 mm with a diamond cutter. This crucible was immersed in a 15 wt% aqueous solution of ammonium acid fluoride for 30 minutes to etch the inner surface at 4 μm. Next, the substrate was washed with ultrapure water and naturally dried in a class 1000 clean room.
Table 3 shows the results of the DF conversion ratio when an 8 ″ single crystal silicon ingot was actually pulled up using the 22 ″ crucible.

[0024]

[Comparative Example 1] IOTA-4 was added to the rotated carbon cylinder of FIG.
The mixture was supplied at Kg / H, and hydrogen chloride gas was supplied at 10 l / min. The furnace temperature was 1250 ° C. The convection time is 30 minutes, and the collected powder is floated with pine oil to remove carbon,
It was washed with a 5% aqueous solution of H202: NH40H = 2: 1. After drying, the purity was checked. Na, K, and Li were measured with a Zeeman atomic absorption spectrophotometer, and the other elements were measured with an ICP emission spectrophotometer. Table 2 shows the results. This raw material sand was put into a rotating SUS water-cooled mold, and a voltage was applied to the arc electrode to melt a 22 ″ quartz glass crucible in 25 minutes.
The melt was taken out, unmelted powder on the outer surface was removed with high-pressure water, and the height was adjusted to 400 mm with a diamond cutter. This crucible was immersed in a 15 wt% aqueous solution of ammonium acid fluoride for 30 minutes to etch the inner surface at 4 μm. Next, the substrate was washed with ultrapure water and naturally dried in a class 1000 clean room. Table 3 shows the results of the DF conversion ratio when an 8 ″ single crystal silicon ingot was actually pulled up using this 22 ″ crucible.

[0025]

[Comparative Example 2] H-8 Sand was added to the rotated carbon cylinder of Fig. 1.
The mixture was supplied at 0 kg / H, and hydrogen chloride gas was supplied at 10 l / min.
The furnace temperature was 1250 ° C. The convection time is 30 minutes, and the collected powder is floated with pine oil to remove carbon,
It was washed with a 5% aqueous solution of H202: NH40H = 2: 1. After drying, the purity was checked. Na, K, and Li were measured with a Zeeman atomic absorption spectrophotometer, and the other elements were measured with an ICP emission spectrophotometer. Table 2 shows the results. This raw material sand was put into a rotating SUS water-cooled mold and a voltage was applied to the arc electrode to melt a 22 ″ quartz glass crucible in 25 minutes. The melt was taken out and unmelted powder on the outer surface was removed with high-pressure water. The height of the crucible was adjusted to 400 mm with a diamond cutter.
It was immersed in an aqueous solution for 30 minutes and the inner surface was etched at 4 μm.
Next, the substrate was washed with ultrapure water and naturally dried in a class 1000 clean room. Table 3 shows the results of the DF conversion ratio when an 8 ″ single crystal silicon ingot was actually pulled up using the 22 ″ crucible.

[0026]

According to the present invention, silicon sand is reduced to 50 ppb or less by passing hydrogen chloride gas and / or chlorine gas at 1300 ° C. or more, which is used as a raw material for a quartz glass crucible. This makes it possible to dramatically improve the yield of crystals, and the manufacturing method of the present invention provides a technique indispensable for manufacturing the quartz glass crucible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used for purifying raw material quartz sand.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon cylinder 2 Heater 3 Material input hopper 4 Material input port 5 Material outlet 6 Hydrogen chloride gas source 7 Hydrogen chloride gas supply port 8 Exhaust port

Claims (1)

[Claims] 1. A raw quartz sand is treated with hydrogen chloride gas and / or chlorine gas at 1300 ° C. or more,
A method for producing a high-purity quartz glass crucible, characterized in that a crucible for pulling single-crystal silicon is produced by a rotary molding method using a raw material quartz sand with Na and K each being 50 ppb or less.