JPH07309615A - Production of synthetic quartz glass powder - Google Patents

Abstract

PURPOSE:To produce synthetic quartz glass powder having high purity, a low OH group content and high viscosity at high temp. and giving a synthetic quartz glass molded article by crushing and classifying a synthetic quartz glass ingot and using the resultant fine powder as starting material. CONSTITUTION:A synthetic quartz glass ingot is mechanically crushed and classified to obtain fine powder of eta200mum particle diameter. This fine powder is treated by one or molds of treatments selected from magnetic separation, flotation, acid treatment and heat treatment and the treated fine powder is used as starting material for a synthetic quartz glass ingot.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing synthetic quartz glass powder, and particularly to a fine powder obtained by crushing and classifying a synthetic quartz glass ingot, which has a high purity, a low OH group content and a high temperature. The present invention relates to a method for producing synthetic quartz glass powder, which gives a synthetic quartz glass molded article having high viscosity.

[0002]

2. Description of the Related Art A semiconductor material such as a crucible for pulling a silicon single crystal and a heat-resistant semiconductor jig are required to have high purity and high heat resistance at the same time. The one made of natural quartz glass is widely used for. This natural quartz glass is used which has been prepared to have a predetermined particle size by mechanical pulverization, and the uniform number n (n = tan α) in the Rosin-Rammler diagram is 3 to
It is preferable to use a material with a particle size distribution of about 8 and a sharp particle size distribution of 150 to 360 μm, but since natural quartz is crystalline, it is relatively easy for this crushed product to have this particle size distribution. It is also known that you can.

On the other hand, various studies have been conducted on the production of silicon single crystal pulling crucibles, heat-resistant semiconductor jigs, etc. from synthetic quartz glass of high purity, but 1).
A method of hydrolyzing silicon tetrachloride in an oxyhydrogen flame to give silica fine particles and melting them to obtain synthetic quartz glass (see US Pat. No. 2,272,342) includes an OH group (≡SiOH) in the glass. However, there is a problem that the high temperature viscosity is low, and foaming occurs at high temperature in vacuum. 2) Silicon tetrachloride is hydrolyzed in an oxyhydrogen flame to give a silica fine particle precursor, The method of melting this into synthetic quartz glass (see Japanese Patent Laid-Open No. 58-125626) and 3) the method of using a plasma flame instead of an oxyhydrogen flame are high in cost and difficult to mass-produce. There is a disadvantage.

Regarding this, 4) Alkoxysilane is hydrolyzed in an alcohol solvent in the presence of an acidic or basic catalyst to synthesize silica sol, which is made into a gel, dried, calcined and sintered. A so-called sol-gel method, in which synthetic quartz glass is obtained by using a sol-gel method, has also been investigated. According to this method, a high-purity product can be obtained relatively easily. It takes a long time to obtain a high-temperature viscous substance, and it is difficult to obtain a high-temperature viscous substance. Furthermore, the carbon content generated by the decomposition of the alkyl group in the alkoxysilane easily mixes into the glass. There is a defect that many bubbles and black spot impurities are generated in the product made from.

Therefore, regarding this, tetramethyl silicate is hydrolyzed in a methanol solvent in the presence of ammonia to synthesize silica primary fine particles, which are calcined,
A method of sintering, crushing and then melting (see JP-A Nos. 2-80329, 2-180723, and 3-5329), and addition of silicon tetrachloride, alkoxysilane, etc. in an oxyhydrogen flame There is also known a method of decomposing silica fine particles, pulverizing a fused synthetic quartz ingot and heat-treating the fused silica ingot to produce quartz glass particles. According to this method, residual OH groups are reduced and highly viscous synthetic It is said that quartz glass can be obtained.

[0006]

However, since this synthetic quartz glass is amorphous, it is difficult to obtain a pulverized product having the above-mentioned particle size distribution, and pulverization by mechanical means causes excessive pulverization. For example, a large amount of fine powder glass with a particle size of 200 μm or less comes out, and this fine powder with a particle size of 200 μm or less is not easy to handle, and even if it is refined and used, the purity and the quality of foreign matter are poor. When vitrified, it foams or has low viscosity at high temperature, and it cannot be used for a crucible for pulling a silicon single crystal or a heat-resistant semiconductor jig.

As for the production of this synthetic quartz glass powder, for example, as shown in FIG. 3, after producing synthetic quartz glass by reaction, it is crushed and classified, and then magnetic separation, flotation, heat treatment, Products are also obtained by performing acid treatment and the like, but this has the disadvantage of being much more expensive than natural quartz because the yield is about 50%.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing synthetic quartz glass powder which solves the above disadvantages, drawbacks and problems, which is to classify synthetic quartz glass ingots mechanically and classify them. Characterized by using the fine powder with a particle size of 200μm or less obtained by one or more of magnetic separation, flotation, acid treatment, and heat treatment, and then using this as a raw material for a synthetic quartz glass ingot. Is.

That is, the inventors of the present invention have conducted various studies to develop a method for producing a synthetic quartz glass powder that can be used in a crucible for pulling a silicon single crystal and a diffusion jig for the semiconductor industry. Mechanically crushed synthetic quartz glass produced by the dry method or dry method, and collected fine powder that had been discarded because it had no conventional use, and the magnetic adhesion quality was kept below a certain value. After that, if this is treated with one or more of magnetic separation, flotation, acid treatment, and heat treatment, it is heated to a high temperature and transparent vitrified does not have black spot impurities, does not generate bubbles, We have found that it will be a viscous synthetic quartz glass, and therefore confirmed that it can be used as a crucible for pulling silicon single crystals and a diffusion jig for the semiconductor industry. The present invention has been completed Te. This will be described in more detail below.

[0010]

The present invention relates to a method for producing synthetic quartz glass powder, which has a particle size of 200 μm obtained by mechanically pulverizing and classifying a synthetic quartz glass ingot as described above.
The following fine powder is treated with one or more of magnetic separation, flotation, acid treatment, and heat treatment, and then used as a raw material for a synthetic quartz glass ingot. According to this, There is an advantage that fine powder, which has been conventionally discarded because it has no use, can be used as a synthetic quartz glass material used for a crucible for pulling a silicon single crystal or a diffusion jig for the semiconductor industry.

In the method for producing synthetic quartz glass powder according to the present invention, a synthetic quartz glass ingot is first mechanically crushed and classified to recover fine powder having a particle size of 200 μm or less. It may be manufactured by any method. Therefore, this was obtained by 1) hydrolyzing tetraalkoxysilane in an aqueous methanol solution using ammonia as a catalyst, and subjecting the resulting slurry suspension containing silica particles to solid-liquid separation, drying, calcination, and sintering, A synthetic quartz glass ingot by a so-called sol-gel method is exemplified.

Regarding the method for producing this ingot, 2) a synthetic quartz glass ingot by a so-called direct method in which silicon tetrachloride, alkoxysilane, etc. are hydrolyzed in an oxyhydrogen flame to form silica fine particles, which are melted. 3) Synthetic quartz glass ingot by so-called soot method in which silicon tetrachloride, alkoxysilane and the like are hydrolyzed in an oxyhydrogen flame to form a silica fine particle precursor, and 4) the oxyhydrogen flame is a plasma flame And
Although any of synthetic quartz glass ingots produced by the plasma method may be used, the dry synthetic quartz glass ingots obtained in 2), 3), and 4) contain a large amount of OH.
In order to remove the group and Cl group for high purification and high viscosity,
It is necessary to previously pulverize and heat-treat under vacuum to normal pressure.

The present invention will be described below in the case of using a synthetic silica glass ingot by the sol-gel method. As tetraalkoxysilane used here, when tetraethoxysilane is used, the OH group content in the synthesized quartz glass increases and the high temperature viscosity becomes low, so it is superior in terms of cost, high reaction rate It is preferable to use tetramethoxysilane, which has excellent properties and has a low OH group content. In this production, tetramethoxysilane is hydrolyzed in a methanol solvent using ammonia as a catalyst to produce silica particles. The particle size of the silica particles is tetramethoxysilane, ammonia, methanol, water weight ratio, reaction temperature, stirring. Controlled by the feed rate and feed rate, the average particle size (including primary particles and agglomerated particles thereof) is required to produce silica powder having a low OH group content and excellent handling properties in subsequent operations.
It is recommended that the thickness is 200 to 5,000 nm.

The silica particle slurry thus obtained is separated by a known solid-liquid separation operation. As this solid-liquid separator, a centrifuge, a filter press, a pressure / vacuum filter are suitable. It The silica particles separated in this way are calcined after being dried in air or oxygen to remove the organic substances and water remaining therein. It is not completely oxidized and remains as black dots, and OH groups remain in the glass due to incomplete opening, and impurities are mixed into the residual pores before the next step of sintering and vitrification. However, if the temperature is set to 1,300 ° C or higher, melting may start and a large amount of bubbles may be generated in the glass. Therefore, this is preferably performed at about 1,000 to 1,300 ° C at which the closing of the silica particles is completed.

When this is subsequently heated in vacuum or in helium gas to about 1,500-1,800 ° C., it is transparent vitrified into a quartz glass ingot, and the thus obtained glass block is crushed, classified, magnetically separated, Flotation,
Quartz glass powder is obtained through purification steps such as hydrochloric acid treatment, hydrofluoric acid treatment, and heat treatment, and the particle size distribution of this is adjusted according to various uses. For example, a relatively coarse grain size 2
Particles of about 50 μm or more are preferably crushed → classified → magnetic separation → magnetic acid treatment → hydrofluoric acid treatment → heat treatment, resulting in a medium grain size.
For those with a size of 250 to 200 μm, it is preferable to perform foam flotation between hydrochloric acid treatment and hydrofluoric acid treatment, but this is appropriately selected depending on the raw material particle size in the quartz glass powder, the magnetic adhesion quality, the amount of foreign matter, etc. It

The same operation is performed for fine particles having a particle size of about 200 μm or less.
If the quality of magnetic particles having a particle size of 200 μm or less is 5% or more, especially 10% or more during classification, the purity of the finally obtained purified quartz glass powder is low and a high viscosity value cannot be obtained.

This crushing is performed by first crushing the glass gob with a coarse crusher such as a jaw crusher or a hammer crusher for 5 to 2 mm.
Granulate to some extent, and then the disc mill, cone mill,
It is industrially preferable to pulverize with a medium pulverizer such as a tube mill or a roll mill, and combine with a classification step to carry out closed circuit pulverization. This crushing is often performed using an iron-based medium because iron is the one that is mixed into the target quartz glass powder due to wear during crushing, because it is easy to remove by magnetic force separation afterwards. , Thus this is for example a lining, a ball mill whose balls are of iron system,
Rod mills, teeth, crush plates, drums are often made of iron-based jaw crushers, disk mills, roller mills, etc., and classifiers and screens should also be iron-based. However, the crushed and classified quartz glass ingot is refined according to the classified particle size as described above.

In this classification step, powder which is unnecessary as a crucible raw material or a diffusion jig raw material is generated due to the particle size distribution of the synthetic quartz glass powder. This is a fine powder with a particle size of 200 μm or less, which is industrially recovered and highly purified by a purification method that combines magnetic separation, flotation, acid treatment, etc., and is recycled as a synthetic quartz glass ingot again. This fine powder should contain a large amount of magnetic particles (for example, 5-15% of silica glass powder of 350-250 μm) in the grinding process.
(2 times), and because it is a fine powder, it entraps quartz glass powder during magnetic separation and the quartz glass powder collides with magnetic particles, causing magnetic interference, and especially magnetic particles are completely removed. Not only a great load is applied to the hydrochloric acid treatment step, but also the magnetic particles cannot be completely removed and the purity of the quartz glass powder is lowered, so that it cannot be reused and is discarded.

As a result of various studies on the method of recovering this fine powder and using it as a synthetic quartz glass powder, the inventors of the present invention found that the magnetic adhesion quality defined by the formula (1) was 10%. Below, it was found that this can be adjusted to a high-purity heat-resistant quartz glass raw material by controlling it to preferably 5% or less, and according to this, it was possible to obtain a high-purity quartz glass powder with a particle size of 200 μm or less. Since it is possible to purify, it was confirmed that this recycle can be used and the yield can be significantly improved. Magnetic adhesion quality (%) = (W ₀ −W ₁ ) / W ₀ × 100 (1) W ₀ : Weight of quartz glass powder before magnetic separation, W ₁ : Quartz glass after magnetic separation Powder weight

Incidentally, this magnetic attachment quality is the weight percentage including the entrained quartz particles after the magnetic separation, and it should be called the apparent magnetic attachment quality (%). Since it is difficult to know the quality, this value is used as the magnetic quality. It is estimated that the increase of magnetic particles in this crushing process is mainly caused by the wear progress of the teeth of the crusher and the crushing plate, but since iron is exclusively used for the material of the crushing teeth and the crushing plate, it is harder than iron. Quartz glass causes these abrasions and chips, and when used for a long period of time, the area of powder contact with the crushing teeth and crushing plate increases, and the magnetic adhesion quality tends to increase over time. The rate of increase depends on the type of crusher selected. Therefore, it is possible to control the magnetic sticking quality to 5% or less by replacing the worn crusher's teeth or the crushing plate before the magnetic sticking quality exceeds 5%.

In order to obtain an industrially sufficiently purified quartz glass ingot from the recovered fine powder, this fine powder is subjected to magnetic separation to remove fine iron powder adhering thereto. Acid treatment with 10-35 wt% hydrochloric acid aqueous solution, and then transfer it to the flotation tank as it is, put pine oil into the foam flotation to remove rubber and other organic substances that cause bubbles during crucible formation. After removing, it is dehydrated and dried.
This product is then calcined at a temperature of 800 to 1,300 ° C to completely remove organic substances such as pine oil. Before this calcination, wash with 2 to 10% by weight of hydrofluoric acid. According to this, coloring after calcination can be prevented, dirt on the particle surface can be removed, and purity can be improved.

The silica glass fine powder treated in this way has a low OH group content of, for example, 1 ppm or less, and it is vacuumed or under normal pressure in the presence of an inert gas.
When heat-treated at a high temperature of 1,700 ° C or higher to make synthetic quartz glass, this one has a high temperature viscosity of 1,400 ° C.
8) × 10 ¹⁰ poise (log η = 10.0 to 10.90), which is a high value, and therefore has the advantage of being useful as a crucible material for pulling a silicon single crystal and a heat-resistant semiconductor jig. Is.

The fine powder having a particle size of 200 μm and whose magnetic adhesion quality is controlled to be 5% or less is recirculated in addition to the raw material glass powder of the quartz glass ingot of the next lot. As the above, the method shown in FIGS. Fig. 1 shows that when the required particle size distribution of product 1 is, for example, 350-200μm in the classification process after medium grinding,
This is a method of recirculating purified fine powder having a particle size of 200 μm or less between the calcination process and the sintering process to significantly improve the yield. 400-3
00μm) and product 2 (for example, particle size 300-200μm) and fine powder with particle size less than 200μm.
Similar to FIG. 1, the refined fine powder of m or less was recirculated between the calcining step and the sintering step to significantly improve the yield.

[0024]

EXAMPLES Next, examples of the present invention will be given. Example 1 A 5 liter reactor was charged with 2.0 liters of 20% by weight aqueous ammonia, and 26.5 liters / hour of methyl silicate and 20
When 17.2 liters / hour of a wt% ammonia water was added dropwise at the same time to react at 40 to 50 ° C. and the reaction was stopped after 5 hours, a silica sol having a silica concentration of about 22 wt% was obtained.

After that, according to the sequence shown in FIG. 1, the product was dehydrated and washed in an ultrapure continuous centrifuge (manufactured by Matsumoto Kikai Co., Ltd.) and then in air to remove residual water and organic matter by oxidation. Calcination at 1,200 ℃ to make openings, and this in vacuum at 1,250 ℃ for 4 hours at 1,500 ℃
When kept at 1,750 ° C. for 1 hour, 51.4 kg of a transparent synthetic quartz glass ingot was obtained. Then, this is roughly crushed into a fist shape 1 (hand crushed with a hammer), and 2 to 3 with 20% by weight of hydrofluoric acid to remove and remove foreign matter adhering to the surface.
After processing for 1 minute, wash with ultrapure water, dry at 180 ° C, and then use a jaw crusher (Oshima Tekko Co., Ltd.) to make coarse particles of 10 mm to several millimeters square, then disc mill (Yoshida Co., Ltd.)
The powder was pulverized with, and classified with a cylindrical classification sieve.

The particle size of the product is 350 to 2 by this classification.
The powder with a particle size of 350 μm adjusted to 00 μm was circulated to the suction of the disk mill again and this circulation was continued until all the particles with a particle size of 350 μm were crushed. Was measured, the particle size was 3
The powder having a particle size of 50 to 200 μm was 27.8 kg, the powder having a particle size of 200 μm under was 22.7 kg, and the particle size distribution of the powder having a particle size of 200 μm under was as shown in Table 2.

Next, the synthetic quartz glass powder adjusted to have a particle size of 350 to 200 μm is pre-magnetically selected by a drum type beneficiation machine (manufactured by Japan Elysees Magnetics Co., Ltd.), and then a coarse selection machine → a selection machine (Dalton). (Made by the company) to remove iron, and at this time, the magnetized material collected in the magnetizer was measured to obtain an approximate magnetized quality. Then, put this in a 20% by weight aqueous hydrochloric acid solution, stir at 40 ° C for 1 hour to perform acid treatment, put it in a double flotation tank, add 140 g of pine oil, and pressurize air from around the stirring rod. While supplying and bubbling for 10 minutes, foreign matter was raised along with bubbles on the water surface to obtain purified synthetic quartz glass powder from the bottom of the final flotation tank, which was dehydrated at 180 ° C.
Final magnetic separation, final hydrofluoric acid washing treatment with 5 wt% hydrofluoric acid, and calcination at 1,050 ° C. in an oxygen atmosphere gave 26.5 kg of the product 1 in FIG.

Further, the particle size after the magnetic separation is 200 μm
Fine powder of under was purified in the same manner as in Product 1 with a particle size of 350 to 200 μm, except that 25% hydrochloric acid was used for hydrochloric acid treatment, four flotation tanks were used for the flotation process, and 10% hydrofluoric acid was used for the final hydrofluoric acid treatment. 19.2 kg of fine powder circulating product was obtained. This circulating product 1 is added between the calcination process and the sintering process as shown in FIG.
At this time, if the tetramethoxysilane hydrolysis reaction time was set to 3 hours and 20 minutes so that the transparent quartz ingot after sintering had almost the same weight (51.4 kg) as after sintering of the previous batch, the calcined powder was 35.0 kg. When the above circulating product 1 was added to this, 52.0 kg of a sintered transparent quartz glass ingot was obtained.

This product was then crushed, classified, and refined to have a particle size of 350 to 200 μm, 27.0 kg, and a particle size of 200.
It became 19.5 kg of under-circulated product with μm. In addition, the product of the batch (the 7th batch from the initial stage) when the crushing time in the disc mill is 24 hours in total is
-2 27.8 kg, recycled product 2 19.2 kg, and the product of the 15th batch whose cumulative period has reached 45 hours is product 1-2 27.2 k
g, circulating product 3 was 18.8 kg, and the accumulated crushing time was 48 hours (16th batch), product 1-3 had 27.9 kg.
Magnetic product quality, purity, OH group content of these products, 1,400
The viscosity at ° C was as shown in Table 1.

As is clear from this table, the circulating product 3 has a magnetic adhesion quality of 5% or more, the products 1 to 3 have reduced purity and high temperature viscosity, and the cumulative crushing time in this disk mill is 25 hours. If the disk (crushing plate) is replaced with a new one when it reaches the limit, the magnetic adhesion quality will be 0.2%, and it will continue to be of high purity.
A synthetic quartz glass powder having a log η at 1,400 ° C of 10.0 poise or more can be stably obtained. Moreover, when quartz glass powder was synthesized by the process of Fig. 1, the yield was about 77%,
This greatly exceeds 50% of the conventional method in which m-under is discarded, and it is also possible to compound the reactor.

[0031]

[Table 1]

[Table 2]

Example 2 In the process shown in FIG. 2, after crushing and classifying, the product particle size is 4
Except for using 3 kinds of product 1 of 00-300 μm, product 2 of particle size 300-200 μm and fine powder of particle size 200 μm under, and using the mass colloider [Masuyuki Sangyo Co., Ltd.] for the medium crusher. The treatment was performed under the same conditions as in Example 1. That is, first, after coarse crushing, medium crushing, and classification in the initial batch, 20.6 kg of powder with a particle size of 400 to 300 μm (after purification, becomes product 1) and powder with a particle size of 300 to 200 μm (after purification with product 2) 12.8 kg, particle size 200 μm Kander (after purification,
17.0 kg was obtained), so this circulating product 1 was added between the calcination step and the sintering step in FIG. 2. At this time, the transparent quartz glass ingot after sintering was burned in the initial batch. When the hydrolysis time of tetramethoxysilane was set to 3 hours and 40 minutes so that the amount was about the same as the weight after binding (51.4 kg),
38.0 kg of calcined powder was obtained, and when the above circulating product 1 was added to this, 51.1 kg of a transparent quartz glass ingot after sintering was obtained.

Then, when the ingot containing the recycled product was crushed, classified and refined, the product having a particle size of 400 to 300 μm, the product having a particle size of 300 to 200 μm and the particle having a particle size of 200 μm were 20.0 kg, 11.5 kg and 14.6 kg, respectively. Was obtained. In addition, regarding this kind of operation, the product 1-1 (1
9.5kg), product 2-1 (12.2kg), recycled product 2 (14.1kg)
In the 15th batch where the cumulative crushing time reached 60 hours, product 1-2 (19.9 kg), product 2-2 (11.6 kg), recycled product 3
(14.6kg) was obtained, and the circulating product 3 had a magnetic adhesion quality of 9.3.
%Met. In addition, 16th batch product 1-3 (20.0k
g) and Product 2-3 (12.2 kg) had reduced purity and high temperature viscosity, and a lot of bubbles were generated in the crucible molded from this quartz glass powder, but from the viewpoint of product yield and quality control. When the crushing teeth of the mass colloider were replaced with new ones after the cumulative crushing time of 48 hours, the magnetic adhesion quality was 0.3%, and the synthetic quartz glass powder with a log η at 1,400 ° C of 10.0 poise or more could be stably obtained. I understood. The results of this series of experiments are shown in Table 3, and the particle size distribution immediately after crushing with a particle size of 200 μm under is as shown in Table 4. Thus, when quartz glass powder was synthesized by the process of FIG. 2, the yield was 81
%, And the particle size of less than 200 μm was discarded by the conventional method 58
The result was significantly higher than%.

[0034]

[Table 3]

[Table 4]

[0035]

Industrial Applicability The present invention relates to a method for producing synthetic quartz glass powder, which comprises mechanically crushing a quartz glass ingot to perform classification, magnetic separation, flotation, acid treatment, and heat treatment as described above. In the method for producing synthetic quartz glass powder, which is a combination of one step or two or more steps, and is refined, if the magnetically-adsorbed article position of the pulverized powder having a particle size of 200 μm or less is 5% or less, the flotation or acid treatment after magnetic separation ,
The heat treatment process can be carried out stably, and granular products with a particle size of 200 μm under, which is high for magnetic products, especially 100 μm under particle size, can be refined to high purity and the quality can be stabilized by recycling. It is possible to achieve higher efficiency, higher yield, and lower costs. The synthetic quartz glass powder produced by such a controlled refining process has few OH groups and high viscosity at high temperature. Therefore, synthetic quartz glass powder that does not contain bubbles and black spot impurities at the time of crucible molding for silicon single crystal is high. Since it can be easily obtained in a yield and the cost is low, it has an advantage that it can be applied in a field where natural quartz powder has been used so far.

[Brief description of drawings]

FIG. 1 is a process diagram of a total circulation process of a synthetic quartz glass powder manufacturing method according to the present invention.

FIG. 2 is a process diagram of a partial circulation process of the synthetic quartz glass powder manufacturing method according to the present invention.

FIG. 3 is a process step diagram of a synthetic quartz glass powder manufacturing method according to a conventional method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michitaka Furusawa 28, Nishi-Fukushima, Chugaku-mura, Nakakubiki-gun, Niigata Prefecture 1 Shin-Etsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A synthetic quartz glass ingot is mechanically crushed and classified to obtain fine powder having a particle size of 200 μm or less, which is subjected to one or more of magnetic separation, flotation, acid treatment and heat treatment. A method for producing a synthetic quartz glass powder, which comprises using this as a raw material for a synthetic quartz glass ingot. 2. The method for producing a synthetic quartz glass powder according to claim 1, wherein the fine powder obtained by crushing and classifying the synthetic quartz glass ingot has a magnetic adhesion quality of 5% or less. 3. A fine powder obtained by crushing and classifying a synthetic quartz glass ingot is Al 50 ppb or less, Fe 30 ppb or less, N
a 10ppb or less, K 10ppb or less, Ca 20ppb or less, Ni1
The method for producing synthetic quartz glass powder according to claim 1, which has a purity of ppb or less, Cr of 5 ppb or less, and U of 0.1 ppb or less. 4. The quartz glass ingot is any one of 1) sol-gel synthetic quartz glass, 2) direct synthetic quartz glass, 3) soot synthetic quartz glass, and 4) plasma synthetic quartz glass. A method for producing the synthetic quartz glass powder described in 1.