JPH0511050B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for refining silicon dioxide (quartz SiO ₂ ), and in particular, to obtaining high-purity silicon dioxide that can be used as a material for the semiconductor industry from general natural quartz ore. About what made it possible. [Prior Art] In addition to being used as a raw material for single crystal silicon and metal silicon, silicon dioxide is also used as a substrate material for IC photomasks, solar cells, etc., mercury lamps and other discharge tubes, and light sources. Used as one of the important materials such as fiber. Among these uses, for example, silicon dioxide used as a filler material for sealing semiconductor integrated circuits (ICs) and transistors is required to be of particularly high purity (ultra-high purity). It is said that the contained impurities iron (Fe) must be 5 ppm or less, aluminum (Al) must be 10 ppm or less, and uranium (U) and thorium (Th) must be 0.3 ppb or less. In this case, the content of impurities such as uranium and thorium is particularly strictly limited, due to α rays caused by the decay of impurities such as uranium contained in the filler material for sealing, as ICs become more highly integrated. This is because the risk of memory elements malfunctioning has increased. By the way, conventional methods for refining silicon dioxide include direct selection of high-purity quartz that exists in natural ore deposits, the so-called VAD method using a fire hydrolysis reaction of silicon tetrachloride and oxygen, and refining by flotation. There were two methods: treating with acid (hydrochloric acid, sulfuric acid, nitric acid, or a mixture thereof), or roasting naturally produced silicon dioxide, pulverizing it at high temperatures, and then leaching it with hydrochloric acid. [Problems to be Solved by the Invention] However, in order to obtain ultra-high purity silicon dioxide that can be used as a filler material for the above-mentioned IC by the above-mentioned conventional method, uranium etc. are originally used as a refining raw material. It was necessary to prepare expensive crystals that could only be produced in extremely limited areas with few impurities. In other words, it has not been possible to obtain ultra-high purity silicon dioxide that satisfies the above conditions even if the conventional refining methods described above use inexpensive natural quartz rough produced in relatively large quantities in a wide area as a raw material. . An object of the present invention is to provide a method for refining silicon dioxide that can obtain ultra-high purity silicon dioxide, which can be used as a material for the filler material for IC encapsulation, from general natural quartz ore. . [Means for Solving the Problems] Against the background described above, the present inventors reexamined the purification principles adopted in each step of conventional purification methods, and found that the impurity content rate in each step was As a result of detailed analysis, we came across a phenomenon in which the analytical value of the impurity content of the granular ore obtained in the crushing process, which is a pre-process to the mineral acid leaching process, varied from measurement to measurement. As a result of investigating the cause of this problem, we found that there was no problem with the analytical equipment, analytical procedures, or general analytical methods such as sampling methods, and the only difference was that the particle size distributions of samples with varying analytical values were different. Therefore, when the raw material ore was crushed, classified by particle size, and the impurity content of each was examined, it was found that the content clearly differed depending on the particle size. That is, the result was obtained that among the crushed raw material ore grains, the percentage of impurities contained in fine grains was always higher than in coarse grains. The present inventors focused on this fact, and as a result of various experiments, by using this principle to remove ore particles with a particle size below a certain level with a high content of impurities, it is possible to achieve purity above a certain level. It was found that ore grains can be obtained, and furthermore, by subjecting the thus obtained highly pure ore grains to a certain refining treatment used in conventional refining processes, the above-mentioned
It was revealed that ultra-high purity silicon dioxide, which can also be used as a filler material for IC encapsulation, can be obtained. The present invention has been made through the process described above, and is a method for refining silicon dioxide, which obtains high-purity silicon dioxide by crushing and leaching raw material ore lumps, the method comprising: A raw material crushing step for crushing lumps, and a step performed after this raw material crushing step, in which ore grains having a particle size smaller than the first standard particle size are removed from the ore grains obtained in the previous step to obtain a first standard particle size. A first sorting/pulverizing step in which the ore grains having the above particle size are selected, taken out, and crushed are repeated one or more times, and the ore grains obtained through this first sorting/pulverizing step are a second sorting step in which only ore grains having a second standard grain size or less are selected from the first reference grain size or less; and a leaching step in which the ore grains obtained through the second sorting step are used as a leaching source ore for leaching treatment. In this case, the first reference particle size is preferably 28 meshes, and the second reference particle size is 150 meshes, and further preferably, the second sorting step The structure is characterized in that a magnetic separation step is performed to remove magnetic substances from the ore grains obtained in the first sorting and crushing step between the leaching step and the leaching step, and more preferably, the leaching step is performed using hydrofluoric acid. The invention is characterized in that it is carried out using a leachate containing. [Function] In the above configuration, there is a tendency that the finer the particle size of the ore particles obtained through the pulverization process, the significantly higher the impurity concentration. Therefore, after the raw material crushing step, out of the ore grains obtained in the previous step, those with a particle size smaller than the first reference particle size are removed, and only the ore particles with a particle size equal to or larger than the first reference particle size are selected and taken out. By performing the first sorting and crushing process in which the crushing process is repeated one or more times, only ore grains with high purity can be taken out. Therefore, by repeating this first sorting and crushing process as many times as necessary, it is possible to obtain extremely high-grade ore grains that could not be obtained through conventional refining processes from ordinary natural quartz ore. The high-grade ore grains obtained in this way are subjected to a second sorting step in which only ore grains having a first standard grain size or less and a second standard grain size or more are sorted from the ore grains to obtain ore grains with a grain size suitable for the leaching process. By selecting and then applying a series of conventionally known leaching and purification methods, ultra-high purity silicon dioxide, which can also be used as an IC filler material, can be obtained with a high yield rate. can. In this case, if normal natural quartz ore is used as the raw material ore, the first standard particle size above is 28
It was confirmed that an ultra-high purity silicon dioxide material can be easily obtained by a relatively simple process by setting the particle size to 150 mesh and setting the second reference particle size to 150 mesh. Furthermore, between the second sorting step and the leaching step, a magnetic separation step is performed to remove the magnetic particles of the ore grains obtained in the first sorting and crushing step, and furthermore, the leaching step is performed using a leachate containing hydrofluoric acid. It has been found that using the above method makes the method more effective. Academic elucidation of the reason why such results are obtained will have to wait for future research, but according to the inventors' hypothesis, naturally produced SiO ₂ rough material has a large effect due to differences in the location where it was quarried. Apart from the difference in impurity content, it is presumed that the impurity content is approximately uniform when viewed macroscopically at the level of the raw material ore grains in the refining stage. Therefore, as in the past, simply crushing the SiO ₂ raw stone to a leachable particle size and leaching it all can only obtain the separation effect by leaching. It is considered that it would have been impossible to obtain silicon dioxide. However, when looking at the SiO ₂ raw stone from a microscopic perspective, it is thought that most of the impurities are concentrated in the same minute region, and these minute regions are distributed at various densities. In this case, the part containing this minute region has a property of being more vulnerable to impact and other physical forces than other regions with less impurities, and as the distribution density of this minute region increases, This trend is expected to become even stronger.
For this reason, when SiO ₂ raw ore is crushed, this brittle portion is crushed first, and it is presumed that as the crushing progresses, the portion with a higher impurity content is crushed into finer ore grains. Therefore, it is thought that high-grade ore grains with high purity can be obtained by removing fine ore grains with a high impurity content from ore grains in a grain size range suitable for leaching. [Example] Hereinafter, a method for purifying silicon dioxide according to an example of the present invention will be described. (Example 1) First, lump ore of SiO ₂ ore from mine A (maximum particle size 300
mm) as a raw material, it is crushed with a dotsuji crusher, the obtained ore grains are sieved with a vibrating sieve, and
28 meshes (more than 28 meshes), 28 to 60 meshes,
The impurity content of each particle was analyzed by particle size of 60 to 150 mesh and -150 mesh (150 mesh or less), and the results were as shown in Attached Table 1. That is, as is clear from Attached Table 1, the finer the particle size, the higher the impurity content. Next, from among the ore grains obtained in the above process, only the ore grains with a mesh size of +28 were taken out, crushed with a roll crusher, divided into particle sizes with a vibrating filter, and analyzed for impurities, as shown in Attached Table 2. It was hot on the street. Furthermore, among the ore grains obtained in the above step, +
Only 28 mesh ore grains were taken out and crushed again using a roll crusher, and then divided into particle sizes using a vibrating sieve in the same manner as above and analyzed for impurity content. The results are shown in Attached Table 3. As is clear from Table 3, the impurity content of -150 mesh particles is extremely high, and the impurity contents of other particle sizes are significantly lower. Then, from among the ore grains obtained in the above step, only 20 to 150 meshes were taken out and subjected to magnetic separation to remove magnetic substances. in this case,
The magnetic force of the magnetically selected material was set to 100 Gauss or more. As a result, the impurity content was 20ppm iron (Fe),
Aluminum (Al) 60ppm, Calcium (Ca)
27ppm, sodium (Na) 11ppm, potassium (K) 3ppm, uranium (U) + thorium (Th)
Ore grains with a grade of 11 ppb were obtained. Next, the ore grains thus obtained were used as a leaching source ore, water was added thereto to prepare a mineral liquid, and leaching treatments were performed under various conditions as described below. That is, an acid concentration of 1N (hereinafter, N
5 kg of sulfuric acid (hereinafter referred to as 5 Kg/t) or 320 kg/t of 8N sulfuric acid is added to each ton of mineral fluid, and to each of these, hydrofluoric acid (concentration; Hydrogen 46%) from 0 to 100
Several values were selected between Kg/t and leaching was carried out at room temperature for about 5 hours. The mineral solution subjected to such leaching treatment is washed and filtered with distilled water, and the wet substances after separation are dried at 160°C for about 16 hours to produce ultra-high purity silicon dioxide as shown in Attached Table 4. I was able to get (Example 2) In the same manner, water was added to the leaching source ore obtained through the magnetic separation process in Example 1 to create mineral liquid, and to this, 70 kg/t of hydrochloric acid with an acid concentration of 2N was added to make several mineral liquids. To these, hydrofluoric acid (concentration: hydrogen fluoride 46%) was added at several values between 0 and 80 kg/t, and then heated at room temperature and 59°C.
After each was subjected to leaching treatment for about 5 hours, each was subjected to drying treatment in the same manner as in Example 1, and the results shown in Attached Table 5 were obtained. (Example 3) In this example, a 50 kg/day purification plant was implemented with reference to the results of Example 1 above. The leaching conditions in this case are as follows. Added sulfuric acid Concentration...8N Added amount...320Kg/t Added hydrofluoric acid Added amount...60Kg/t Leaching temperature...Room temperature Leaching time...5 hours Drying conditions Temperature...160℃ Time...16 hours As a result , the results shown in Attached Table 6 were obtained. (Example 4) In the refining plant of Example 3, the leaching process was carried out under the same conditions except that the added sulfuric acid and hydrofluoric acid were changed to 180 kg/t and 40 kg/t, respectively. The results shown were obtained. From the above results, it is clear that in each of the examples, ultra-high purity silicon dioxide, which can be used as a filler material for IC encapsulation, is recovered at an extremely high rate not only in the laboratory but also in industrial plants. It can be seen that even the ratio can be obtained. Next, the present inventors also attempted purification by a conventional purification method by leaching, and some of the results are listed below as a comparative example. (Comparative Example 1) Using raw _SiO2 from mine A (maximum particle size 300 mm) as a raw material, crush it with a dotsuji crusher, then sieve it with a vibrating sieve, and leach -28 mesh. It was originally a mine. Next, water is added to this leaching source ore to make several mineral liquids, and 320 kg/t of 98% concentrated sulfuric acid and 100 kg/t of 36% hydrochloric acid are added to these to make the mineral liquids have a sulfuric acid concentration of 8N and a concentration of 8N, respectively. Leaching was carried out at room temperature or 59°C for about 5 hours with a hydrochloric acid concentration of 3N. The mineral solution thus obtained was subjected to a drying treatment at 160°C for about 5 hours, and the results shown in Attached Table 8 were obtained. (Comparative Example 2) In Comparative Example 1, treatment was carried out under the same conditions as in Comparative Example 1, except that 24 kg/t of hydrofluoric acid was added to increase the leaching effect during the leaching treatment. The results shown are obtained. (Comparative Example 3) In this example, a magnetic separation step was added to Comparative Example 1, and the results shown in Appendix 10 were obtained. (Comparative Example 4) In this example, a magnetic separation process was added to Comparative Example 2, and the results shown in Appendix 11 were obtained. As mentioned above, in Comparative Example 1, the impurity content was 18 to 30 ppm for iron and 89 to 30 ppm for aluminum.
101ppm, calcium 42~44ppm, potassium 34~
39ppm, uranium + thorium 1-2ppb,
Comparative Examples 2 to 3 were extremely insufficient and added hydrofluoric acid or a magnetic separation process
Even in Example 4, the quality was improved compared to Comparative Example 1, but the purity was far short of the purity required for the filler material for IC encapsulation. In addition, in each of the above examples, quartz rough from Mine A, which has a relatively high iron content, is used, and a dotsushi crusher is used for crushing, so there will be some iron mixed in, so the leaching process In the previous section, we gave an example in which a magnetic separation process is used to remove magnetic substances, but if the raw ore with a relatively low iron content is used, and another crushing device that does not mix iron without using a double crusher is used. , it is not necessary to necessarily include the magnetic separation process, and if raw ore with a lower impurity content than that from mine A is used, the effects of the present invention can be obtained without adding the hydrofluoric acid. has been confirmed in other experiments by the inventors. Further, although the ore grains are sorted using a vibrating sieve, it goes without saying that other sorting means such as water washing and desliming may also be used. [Effects of the Invention] As detailed above, the method for refining silicon dioxide according to the present invention involves crushing and leaching natural quartz ore produced in a relatively wide area.
After the raw material crushing step, remove ore grains with a particle size smaller than the first reference particle size from among the ore particles obtained in the previous step, and select and take out only the ore particles with a particle size equal to or higher than the first reference particle size, and crush them. A first sorting and crushing step in which the treatment is repeated one or more times is performed to obtain extremely high-grade ore grains, and then the high-grade ore grains obtained in this way are subjected to a first sorting and crushing step in which the treatment is repeated one or more times. A second sorting process is performed to select only ore grains with a second reference grain size or higher to select ore grains with a grain size suitable for the leaching process, and then a series of leaching and purification methods are applied to produce IC. This makes it possible to obtain ultra-high purity silicon dioxide, which can also be used as a filler material, with a high yield rate.

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Claims (1)

[Scope of Claims] 1. A method for refining silicon dioxide for obtaining high-purity silicon dioxide by pulverizing raw material ore lumps and subjecting them to leaching treatment, comprising: a raw material crushing step of pulverizing the raw material ore lumps; This is a step performed after this raw material crushing step, in which ore grains with a particle size smaller than the first reference particle size are removed from the ore particles obtained in the previous step, and only ore particles with a particle size equal to or larger than the first reference particle size are sorted. a first sorting/pulverizing process in which the ore particles are taken out and crushed one or more times, and the ore grains obtained through the first sorting/pulverizing process have a particle size equal to or less than the first standard particle size. A method for refining silicon dioxide, comprising: a second sorting step in which only ore grains having a particle size or higher are sorted; and a leaching step in which the ore grains obtained through the second sorting step are used as a source ore for leaching. 2 The first reference particle size is 28 mesh, and the second
The method for purifying silicon dioxide according to claim 1, wherein the standard particle size is 150 mesh. 3. Claims 1 or 2, characterized in that between the second sorting step and the leaching step, a magnetic separation step is performed to remove magnetic substances from the ore grains obtained in the first crushing and sorting step. A method for purifying silicon dioxide. 4. The method for refining silicon dioxide according to any one of claims 1 to 3, wherein the leaching step is performed using a leaching solution containing hydrofluoric acid.