JP2723643B2 - Manufacturing method of synthetic quartz glass crucible - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is useful for pulling a silicon single crystal because of a small amount of erosion when used for pulling a synthetic quartz glass crucible, particularly a silicon single crystal. The present invention relates to a synthetic quartz glass crucible and a method for producing the same.

(Prior art) As semiconductor devices become more highly integrated, the yield of the devices is decreasing, and it is necessary to improve the purity of silicon wafers to prevent the generation of micro defects. A great deal of research investment has been made here, but in order to improve the purity of silicon wafers, in other words, to prevent its contamination, it is necessary to increase the purity of the peripheral materials used here. Crucibles are also targeted.

For the purpose of purifying this crucible, for example, B
A method in which the content, the OH group content, the transition metal, and the alkali metal content are set to predetermined amounts or less, respectively, to increase the purity of the crucible and reduce the amount of erosion (see Japanese Patent Publication No. 58-49519); A technique for lowering minute defects with a ppm or less (see Japanese Patent Application Laid-Open No. 60-137892) has been proposed.
This synthetic quartz glass crucible has a synthetic quartz glass layer formed on the inner surface of a natural quartz glass crucible.
58-50955 and JP-A-61-44793) are also proposed.

(Problems to be Solved by the Invention) However, these conventionally known synthetic quartz glasses still have a rate of erosion to silicon melt at the time of pulling a silicon single crystal which is two to three times faster than that of natural quartz glass. Since the amount is 1.5 to 3 μg / cm ² · sec,
This is a fatal defect as a crucible.

In addition, when the silicon single crystal is pulled, the device is in a supersaturated state at a temperature of 1,200 ° C. or lower and the precipitation of oxygen (including the generation of crystal defects) occurs. Therefore, the silicon single crystal is pulled by the MCZ method. Has been proposed, but even in this case, there is a disadvantage that the effect is small because melting and melting of the silicon melt and the crucible occur due to the oxidation-reduction reaction.

(Means for Solving the Problems) The present invention relates to a method for producing a synthetic quartz glass crucible capable of solving such disadvantages, which comprises a colloidal silica produced by a sol-gel method using a strong alkaline catalyst from alkoxysilane. And calcine it,
After decarburization and desolvation, it was further treated at high temperature to vitrify to obtain a synthetic quartz powder, which was then sintered and molded by an arc flame, and the melting rate at the time of pulling up a silicon single crystal became 1
The present invention relates to a method for producing a synthetic quartz glass crucible characterized by being a synthetic quartz glass crucible having a value of not more than μg / cm ² · sec.

That is, as a result of various studies on the modification of a synthetic quartz glass crucible used for pulling a silicon single crystal, the present inventors found that the melting rate of the synthetic quartz glass crucible used for pulling a silicon single crystal was 1 μg / cm ^2. · When it is sec or more small defects in the silicon single crystal is increased, but this erosion rate 1 [mu] g / cm ² · sec or less, 0.6 [mu] g / cm ² · sec or less and preferably erosion rate of natural silica glass In addition to finding that the increase of micro defects in silicon single crystal is suppressed, and pursuing the erosion mechanism of quartz glass crucible to silicon melt, this is because oxygen dissolves in silicon, and Is silica (SiO ₂ ) that constitutes quartz glass
The problem is whether or not has a highly reactive structure, but colloidal silica obtained by a sol-gel method using a strong alkali catalyst from alkoxysilane has a very tight structure. The present inventors have found that the synthetic quartz glass crucible thus manufactured has an amount of erosion of 1 μg / cm ² · sec or less, thereby completing the present invention. This will be described in more detail below.

(Function) The present invention relates to a method for producing a synthetic quartz glass crucible used for pulling a silicon single crystal.

The pulling of silicon single crystal is performed by melting silicon in a quartz glass crucible, immersing a silicon seed crystal in this, and pulling it up.However, since this pulling is performed at a high temperature under the melting of silicon, It is known that silica (SiO ₂ ) constituting a quartz glass crucible is dissolved in a silicon melt in a very small amount, and this causes micro defects in a silicon single crystal.

Therefore, various studies were conducted on the generation of micro defects during the pulling of silicon.
μg / cm ² · Although the sec is more than slight defects in the silicon crystal occurs, this is 1 [mu] g / cm ² · sec or less, preferably below 0.6 [mu] g / cm ² · sec is erosion rate of natural silica glass It has been found that micro defects do not occur in the silicon crystal if it is present. Therefore, the synthetic quartz glass crucible used when pulling the silicon single crystal has a melting rate of 1 μg / cm ² sec or less. It was confirmed that it should be.

In addition, when pursuing the mechanism of silica erosion during pulling of a silicon single crystal, the reason is that oxygen in the silica dissolves into the silicon. Therefore, when the silica has a highly reactive structure, the amount of erosion is reduced. Increase, that is, energy at high temperature
It was found that when the bond of O was easily broken, there was much erosion, but when it was hard to break, the erosion was small.

On the other hand, the present inventors are studying the production of quartz glass by the sol-gel method, but the structure of colloidal silica made from alkoxysilane by the sol-gel method using a strong alkali catalyst is very tight. Because of that,
The colloidal silica obtained by this sol-gel method is calcined, decarburized and desolventized, and then sintered and molded using a high-temperature treated vitrified quartz glass particle using an arc flame. In the case of a synthetic quartz glass crucible, this colloidal silica has a regular three-dimensional matrix and has a strong covalent bond. Therefore, the bond is hard to be broken even at a high temperature, and this property is maintained even when molded into a crucible. Therefore, when a synthetic quartz glass crucible made in this way is used when pulling a silicon single crystal, the oxidation-reduction reaction is suppressed, and the erosion rate becomes 1 μg / cm ² · sec or less. Therefore, it was confirmed that the material was useful as a crucible for pulling a silicon single crystal.

(Examples) Examples of the present invention and comparative examples will be described below.

Example 1, Comparative Examples 1-2 Methyl silicate 26.5 / hour and 20% by weight of aqueous ammonia 17.2 / hour were simultaneously dropped into a reaction flask of 5 and reacted at 40-50 ° C., and the reaction was stopped after 5 hours. As a result, a silica sol solution having a silica concentration of 23% was obtained.
This was dehydrated to produce silica having a water content of 25% by weight.

Next, 8 kg of this silica was dispersed in ultrapure water 8, and 29% by weight of ammonia water 350 was added thereto to adjust the pH to 11, and methyl silicate was added to this silica in an amount of 10% by weight in terms of silica. This is solidified, calcined,
After decarburization and desolvation, from room temperature to 1,000 in air
The temperature was raised to 0 ° C. over 13 hours, and then kept at 1,000 ° C. for 1 hour to obtain a synthetic quartz glass powder, and the powder was subjected to 30 to 100 mesh using a 30-mesh sieve made of polypropylene and a 100-mesh sieve made of Teflon. The pieces were sieved and placed in a quartz glass crucible having a diameter of 12 inches.

Next, put this crucible under argon gas atmosphere for 1 hour.
The temperature was raised to 1,500 ° C., kept at this temperature for 2 hours to form a transparent vitrified silica, taken out after cooling, then crushed with a quartz glass roller, and sieved with a 50-mesh or 100-mesh sieve made of Teflon. However, since synthetic quartz glass powder was obtained at a yield of 95%, this synthetic quartz glass powder was molded into a crucible by a known method using an arc flame, and the crucible exhibited the physical properties shown in Table 1. As shown, the physical properties of the natural quartz glass crucible prepared for comparison and the synthetic quartz plate made by the flame method were examined. The results were as shown in Table 1.

Next, a synthetic quartz glass crucible of the present invention having an inner diameter of 18 inches produced by the method described above, a natural quartz glass crucible for comparison, and a synthetic quartz glass crucible produced by a flame method, 60 kg of silicon polycrystal were placed in the crucible. This was melted at 1,520 ° C., immersed in a polished quartz glass sample of 20 × 7 × 100 mm, rotated at a speed of 1 rpm for 5 hours, pulled up, and treated at 1,000 ° C. with HCl gas. The difference between the weight before the treatment and the weight after the treatment was divided by the contact area and the time to determine the erosion weight. The results shown in Table 2 were obtained.

In addition, 80 kg of silicon polycrystal was put into the three types of crucibles of 18 inches in the above, melted at 1,520 ° C., then immersed in a silicon single crystal, and pulled up a 6-inch silicon single crystal ingot by 650 mm. When the oxygen concentration and the microscopic defect (OSF) were examined, the results shown in Table 3 were obtained.

(Effect of the Invention) According to the present invention, a synthetic quartz glass crucible having a melting rate of 1 μg / cm ² · sec or less when pulling a silicon single crystal can be obtained. When used, the effect of suppressing the oxidation-reduction reaction and preventing the generation of minute defects in the silicon crystal is obtained.

Claims (1)

(57) [Claims] A colloidal silica is produced from an alkoxysilane by a sol-gel method using a strong alkaline catalyst,
After calcining, decarburizing and desolvating, it is further processed at a high temperature to vitrify it to obtain a synthetic quartz glass powder, which is then sintered and molded by an arc flame to melt the silicon single crystal at the time of pulling. A synthetic quartz glass crucible having a loss rate of 1 μg / cm ² · sec or less.