JPS6256306A - Method for purifying hydrofluoric acid - Google Patents

Abstract

PURPOSE:To reduce the content of impurities to a ppb level by adding fluorine to hydrofluoric acid wherein the compd. of at least one nonmetallic element among boron, silicon, phosphorus, sulfur and chlorine is dissolved as the impurities, allowing the impurities to react with the fluorine and then distilling the acid. CONSTITUTION:Fluorine is added to hydrofluoric acid wherein the compd. of at least one nonmetallic element selected from a group of boron, silicon, phosphorus, sulfur and chlorine is dissolved and allowed to react with the compd. The acid is then distilled. By such a method, almost all the impurities can be easily concentrated and obtained in the initial fraction as the distillate. Fluorine is charged into the reaction system in the form of gaseous fluorine, a mixture of an inert gas and fluorine or the soln. of gaseous fluorine in an inert liq. such as hydrofluoric acid. The reaction of the impurities with gaseous fluorine is preferably carried out at -20-+20 deg.C and at atmospheric pressure.

Description

[Detailed description of the invention] [Industrial application field] The present invention removes and purifies each compound of boron, silicon, phosphorus, sulfur, and chlorine that exists as impurities in hydrofluoric acid. The present invention relates to a completely new method for obtaining ultra-high purity hydrofluoric acid, which has been reduced to an ultra-trace level. Purified hydrofluoric acid and the hydrofluoride salts produced from it are in great demand as important chemicals in the electronics industry, and are in particular used regularly as essential materials in numerous processing steps from semiconductor wafers to devices. As the degree of integration of semiconductors increases, the demand for high-purity products is increasing.

Boron, silicon, phosphorus, sulfur and chlorine are each
It is a nonmetallic element belonging to mb, ■b, vb, vib, and ■b in the Shuho table, and the presence of these elements and compounds are obstacles to semiconductor devices.
It must be said that removing and purifying these impurities from hydrofluoric acid will greatly contribute to the advancement of semiconductors. In addition, various fluorine compounds are used in many new technical fields such as optical-related industrial materials, solar cell materials, and new ceramic raw materials, but the demand for high-purity hydrofluoric acid as a starting material for these Hunto compounds is increasing. It's very strong.

[Prior Art] and [Problems to be Solved by the Invention] Elements such as boron, silicon, phosphorus, sulfur and chlorine usually exist in hydrofluoric acid as compounds represented by the following chemical formula. It is known that there are

11BF4. 1hsiF6. tlPFi,, H3
(hF, llCl) Of course, these are the main forms of existence, and it is also known that they exist in the form of compounds with various compositions, and these compounds can only be extracted by distillation. It is known that it can be removed and purified to a certain extent.

That is, during normal distillation, boron, silicon, phosphorus, and chlorine compounds are BP:i, SiF4゜P, respectively.
It is concentrated in the first distillation part as a low-boiling fraction such as FS and ICI, and among the sulfur compounds, the S (h form) is in the low-boiling point fraction, and the SO, form is in the low-boiling point fraction. It has been found that the impurities can be purified to ppm level by these methods, and to date, the purity of hydrofluoric acid has not been improved. The requirements for commercially available products were only down to the ppm level.Therefore, there was no debate as to whether it would be possible to purify hydrofluoric acid to an ultra-trace amount. (Of course, there were no documents or patents regarding this. For example, even in the current standards for hydrofluoric acid for semiconductors, which require high purity, these impurities are only specified to the ppm level. Moreover, the current hydrofluoric acid test force method for semiconductors (JIS K 1466 1964) cannot analyze these impurities down to the ppb level.

Furthermore, Table 1 summarizes the specifications for the above-mentioned compounds in the US standards for hydrofluoric acid for semiconductors.

Table-1 SEMI 5TANDARD C1, STD, 8 fo
r Hydrofluoric Ac1d In order to establish a method for producing ultra-high purity hydrofluoric acid, which is required by cutting-edge technology, the present inventor first conducted research on the development of an ultra-trace analysis method, and These compounds I
) He discovered an analytical method that could measure down to the PB level, and succeeded in improving it into a technology that could be put to practical use5.

By conducting a precise study of the behavior of impurities, they discovered a complex phenomenon that had not been previously known, and discovered that this phenomenon made it extremely difficult to purify the impurities.

In other words, for example, in the case of sulfur compounds, an equilibrium of the following formula appears to exist due to dissociation in the presence of water, and common sense suggests that any form is a higher boiling point fraction than hydrogen fluoride. It is thought that during distillation, all of them remain on the high-boiling side.

(a) 1lsO3F + 11204 HzSOJ+
However, the inventor's precise experiments surprisingly revealed that both the initial distillate component and the trailing distillate component contained components measured as SO and ions. It is also recognized that boron is difficult to distill into the initial distillation depending on the concentration of coexisting water. In particular, the reaction between impurities and moisture is complex, and the compounds of boron, silicon, phosphorus, and chlorine are in the following chemical equilibrium with the moisture present in the system.

(b) HBF, +1120';:2 118
F:1(Oll)+IIF(C) 1IBF1(0
11) + 1IzO: HBFz(011)z +
Liver (d) (+10)2POF+ It□o:
I, POJ + IIF(e) (HO)P
OF2+ 1lzO';: (HO)zP04+
IIF (f) POh +1120 4 (110)
POFz + IIF(g) PFs + II
zO: POh+2HF(h)2+1□5iFa+
2H20ヰ 5iFa + 5it)z + 811
F(i) llCl + II□o 4 hc
The compounds that exist or can exist in each of the above equilibrium reactions are listed below.

(i) Boron compounds C1, BZF4. )lBF4. IIBF: +(O
ff), )lLiver 2(011)2(ii) Phosphorus compounds PFff, PFs, 1lPh, (H
O)zPOF, (110)POF! , P.O.
F3(iii) Sulfur compounds SFa, SFb, 52FIO,5OFA, SO2
F2. l1SOtF(iv) Silicon compound 5iFn, 5izFa, Il, 5iFt, + (S
iFz) 20(v) Compounds of chlorine HCI, II□FCI, 1hcI.

(vi) Mutual compound of the above elements BCl3. PCi5.3FSCI Conventional analytical techniques cannot detect the presence or absence of these compounds @ p
Although it is impossible to confirm the concentration below pm, this is because each impurity element exists in various compound forms, and the vapor-liquid equilibrium relationship is therefore multiphase, multidimensional, and complex. It also depends on who you are. When these impurities actually reach concentrations at the ρpb level, they exhibit unusual behavior under distillation conditions that cannot be considered as 1PL-compounds, resulting in extremely poor rectification efficiency and conventional methods. This has made it impossible to purify to ppb level using known methods.

[Means for Solving the Problems] and [Operations] As a result of numerous studies conducted on the purification of hydrofluoric acid, the present inventor has found that hydrofluoric acid can be pretreated by a special method and then distilled. or just by special treatment during distillation.
They developed a common method for removing all of these impurities, and succeeded in developing a purification method that allows them to obtain ultra-high purity hydrofluoric acid.

That is, the present invention involves adding fluorine 7 to hydrofluoric acid in which a compound of at least one nonmetallic element selected from the group consisting of boron, silicon, phosphorus, sulfur, and chlorine is dissolved, and causing a reaction. It was later discovered that by distilling seven distillates, almost all of these impurities were easily concentrated in the first distillate and distilled out, and that this method was an excellent method for purifying hydrofluoric acid. This made it clear that

An example of the experimental results of this effect is shown in Table 2. Of course, these data may change depending on the concentration of each component, temperature, amount of additives, and other conditions, but it is possible that impurities are concentrated in the initial distillate. ? r l? The strong tendency to be i-ed remained unchanged throughout all experiments.

The operation of adding fluorine to hydrofluoric acid may be carried out before distillation, or may be carried out during distillation. In this case, fluorine is introduced into the reaction system in the form of fluorine gas 7, as a mixed fluorine gas with an inert gas, or in the form of a solution of fluorine gas dissolved in an inert liquid such as hydrogen fluoride. The reaction between impurities and fluorine gas is -40 to +400℃
(It may be under reduced pressure, normal pressure, or increased pressure), preferably at -20 to +20°C, and under normal pressure. The reaction to fluorinate the gas starts, and the higher the temperature, the faster this reaction progresses.

Table 2 The first possible reason for the remarkable effect of fluorine addition treatment is that its fundamental effect is to forcibly transform impurities into low-boiling fluorine compounds due to its strong reactivity. I guess that's what it means. For example -1', n-
U compound is concentrated in the first distillation l+h, 5OzFz,
This is because it changes into a compound with an extremely low boiling point such as 5OFz in a very short time.

The second possible effect of fluorine addition treatment is that its strong oxidation and dehydration power removes coexisting water, etc., and also reduces the amount of water and impurities shown in (a) to (i) above. The objective is to thoroughly resolve complex equilibrium relationships.

For example, fluorine reacts instantaneously with water and converts into OF2.02゜03, etc., which can be easily removed from the system as a low-boiling point gas, and is used for distillation purification of hydrofluoric acid. It leaves no obstacles behind.

Fz” IIzO= IIF +OFZ + II□
02+0°+03 [Example] The present inventors conducted numerous experiments and completed the present invention.
The superiority of the present invention has been confirmed, and several representative examples will be extracted and shown below as examples. Therefore, the present invention is not limited to the embodiments described below, and it goes without saying that the embodiments may be modified and implemented as desired without departing from the spirit and gist of the present invention. The hydrofluoric acid raw material used in the following examples contains at least the impurities shown in Table 1.

Example 1 80% of hydrofluoric acid was added to a polychlorofluoroethylene A container (capacity 1β) equipped with a reflux condenser and a distillation tube.
05r and fluorine gas (17298, 6%).

11F1.4%) from the cylinder at 80ppm based on the raw material.
After dissolving the solution by blowing it in at room temperature, the container is heated to perform rectification. First, the initial distillate is removed, and then the hydrofluoric acid fraction (bp, 20° C.) is collected as the main distillate.

This purified hydrofluoric acid contained only the following impurities and was truly suitable as hydrofluoric acid for electronic materials.

B Si, POa 5O4CI Example 2 Using the same equipment as in Example 1, 800 g of hydrofluoric acid was added to the container.
fluorine gas generated from a fluorine electrolytic tank (
F, 89.8%, ilF 10.2%) was blown at 0.4g as F2 and dissolved at -10°C, then the container was heated and hydrofluoric acid was distilled to obtain purified hydrofluoric acid. . The impurities in this purified hydrofluoric acid were measured and found to be as follows.

B Si PO45Oa C1 Example 3 A rectification apparatus that can be operated continuously and has a cooler and a packed tower made of polytetrafluoroethylene is used. In order to charge the raw material hydrofluoric acid into this device, it is connected to a continuous supply section installed at the bottom of the device, and a thin tube for introducing fluorine gas from the fluorine electrolytic cell (2) is connected to the continuous supply section provided at the bottom of the device. While continuously charging raw material hydrofluoric acid at a rate of 80 kg/hour, fluorine gas (F288.6%, l 1
1.4%) was continuously blown into the raw material hydrofluoric acid from the gas supply port so that the amount of fluorine was 1100 pp, heated to around 20° C., and rectified. A light fraction is extracted from the distillation tube at the top of the rectification column, and hydrofluoric acid is distilled and collected from distillation tubes No. 2 and 3 below the top. In this way 1
The amount of impurities in purified hydrofluoric acid obtained by continuous operation for 0 hours was measured and found to be as follows.

B Si f'oa SOa C1 Purified Hydrofluoric Acid 24 3 45 or less (ppb) [Effects of the Invention] This is a truly groundbreaking invention in that it made it possible to produce ultra-high purity hydrofluoric acid. We are now able to fully meet the demands of various industrial fields that require electronic materials and fine chemicals, and are also becoming popular as materials for research and other purposes that require precision in various areas of cutting-edge technology. We are now able to meet the expectations of It has also become possible to synthesize ultra-high purity fluorine compounds using this hydrofluoric acid as a raw material.

Hand U and (spontaneous writing by Hosho) 5゜1. Display of the case 1985 Patent Application No. 194140 2 Name of the invention Method for purifying hydrofluoric acid 3 Person making the amendment Relationship to the case For patent) Applicant 7-227 Kaiyama-cho, Sakai City, Osaka Prefecture Representative Michinosuke Hashimoto 4, 1-Detailed explanation of the invention of the specification subject to the agent's amendment 1 Contents of the amendment as per the attached full text corrected specification. However, there are no changes to the contents except for the fields listed in the subject of amendment in the previous paragraph.

Full text corrected specification 1, Title of the invention Method for purifying hydrofluoric acid 2, Claims ■ A compound of at least one nonmetallic element selected from the group consisting of boron, silicon, phosphorus, sulfur, and chlorine is dissolved. A method for purifying hydrofluoric acid, which is characterized by adding fluorine to hydrofluoric acid, reacting it, and then purifying it by distillation.

3. Detailed Description of the Invention [Field of Industrial Application] The present invention removes and purifies boron, silicon, phosphorus, sulfur, and chlorine compounds that exist as impurities in hydrofluoric acid, reducing them to ultra-trace amounts at ppb level. This invention relates to a completely new method for obtaining ultra-high purity hydrofluoric acid. Purified hydrofluoric acid and the hydrofluoric acid salts produced from it are in great demand as important chemicals in the electronics industry, and are commonly used as indispensable raw materials in numerous processing steps, from semiconductor wafers to devices. As the degree of integration of semiconductors increases,
The demand for high-purity products is increasing7.

Boron, silicon, phosphorus, sulfur and chlorine are each
It is a nonmetallic element that belongs to mb, rvb, vb, vib, and b in the periodic table.The presence of these elements and compounds are obstacles to semiconductor devices, so these impurities can be removed from hydrofluoric acid. It must be said that removal and purification greatly contribute to the progress of semiconductors. Also optical related industrial materials, solar cells'
J Category A, 21-A large number of various fluorine compounds are used in new technical fields such as ceramic raw materials, and there is a very strong demand for high-purity fluorinated acid as a starting material for these fluorine compounds. be.

[Prior art] and (problem to be solved by the invention) Elements such as boron, silicon, phosphorus, sulfur and chlorine usually exist in hydrofluoric acid as compounds represented by the following chemical formula, It is known that

1tllF4. 1hsiFh, tlPFi,,
1IsO3F, IIcI Of course, these are the main forms of existence, and in addition to Kone et al., they exist in the form of a variety of Vfl-forming compounds.

It is also known that these monsters are found on cliffs.
It is known that it is possible to remove and purify to a certain extent only by using 7.

1- That is, when the normal body W1 is used,
Compounds of ion, phosphorus and chlorine each have IF3. Si
F.

r'FS, lIc+ are concentrated in the initial distillation fraction as low-boiling fractions, and the bottom of the sulfur compounds is SO
It has been found that the form 7 is distilled out in the low boiling point Wj fraction, and the form S(h is separated into the specific IF, two high boiling point fractions. Their method can purify impurities to ppm level, and at present, the purity requirements for hydrofluoric acid are at ppm level.
The city was only required to use water up to the pm level. For example, even in the standards for hydrofluoric acid for semiconductors, which require high purity, these impurities are limited to ppm.
It is only specified up to the level.

Further, Table 1 summarizes the specifications for the above compounds in the US standards for hydrofluoric acid for semiconductors.

Table-1 SEMI 5TANnARD C1, STD, 8
for l1ydrofluoric Ac1d
As described above, hydrofluoric acid obtained by conventional purification methods is no longer able to meet the demand for even higher purity hydrofluoric acid as a result of recent advances in technology.

[Problem that the invention seeks to solve]

The problem that the present invention seeks to solve is to provide highly purified fluorinated water (hydrofluoric acid) and acid that can meet the above requirements. The aim is to develop new purification methods that can be obtained.

In order to solve these problems, the present inventor conducted a precise study of the /i3 behavior of these impurities during the distillation process of hydrofluoric acid, and discovered a complex phenomenon that had not been previously known. It was discovered that this phenomenon made purification of impurities extremely difficult.

In other words, for example, in the case of sulfur compounds, an equilibrium of the following formula appears to exist due to dissociation in the presence of water, and common sense suggests that any form is a higher boiling point fraction than hydrogen fluoride. It is thought that both steam and water remain on the high-boiling side.

(a) IISO:lF→-tlzo: 11250
4+ Liver However, in precise experiments conducted by the present inventor, it was surprisingly found that both the initial distillation component and the junior component contained components measured as SO and ions. It is also recognized that boron can be distilled into the first distillate depending on the concentration of coexisting water.

In particular, the reaction between impurities and water is complicated, and boron.

The compounds of silicon, phosphorus, and chlorine interact with the water present in the system in the following chemical way.

(b) 1 (BP 4+ II 20: HB
F z (Kano) + IIF (c) IIRFi (Of (
) + IIzO';;: 1(BFz(Ol
l)z + IIF(d) (110)
2POF + tl□0 ko H, PO4+ II
F(e) (HO)POFz← +, izo:
()10)7:PO,+IIF(f)POF3+
HzO;; (HO)Potton2+)IF(g)
PFS+)120 ;↑
POF! ”211F(h,)211□5i
Fb ± 211□0, fi SiF4+ 5
i02 + 811F(i) HCI + 1
120''; f: Il:1CIO The list of compounds that exist or can exist in each of the above equilibrium reactions is as follows.

(i) Boron compound BF3.8ZF, IIBF, IIBF, (OH
), H1IF2(Oll)2(ii) Phosphorous compound PF3. PFS, 1IPFb, (ItO)zPO
F, (tlo)POFz, POF3(iii) sulfur compound 'SF4. SFb, 52FIO, SOF2. S.O.
2F2.1lsO3F< iv) Silicon compound SiF4. Si, zF6.1lzsiF6. (Si
Ft) zO (v) Compounds of chlorine +1CI, H□FCI, H, Cl0 (vl) Mutual compounds of the above elements BCh, PCl3. SF! , CI Conventional analytical techniques cannot determine the presence or absence of these compounds by pp.
Although it is completely impossible to confirm temperatures below m, as mentioned above, each impurity element exists in various compound forms, and therefore the gas-liquid equilibrium relationship is multiphase, multidimensional, and complex. It has just become, and under the feudal rule,
It is thought that the 64 compound exhibits unusual behavior that cannot be considered to be a single compound, and as a result, the rectification efficiency becomes extremely low, making it impossible to purify it to the ppb level using conventional known methods. .

[Means for Solving the Problems] As a result of conducting numerous studies on the purification of hydrofluoric acid, the present inventor has found that hydrofluoric acid is pretreated by a special method and distilled, or distilled. They succeeded in developing a common method to remove all of these impurities by simply performing special treatment on the inside, and a purification method that can obtain ultra-high purity hydrofluoric acid.

Of course, the present invention involves adding fluorine to hydrofluoric acid in which a compound of at least one nonmetallic element selected from the group consisting of boron, silica, phosphorus, sulfur, and chlorine is dissolved and causing the reaction. Afterwards, it was discovered that almost all of these impurities were easily concentrated and distilled out in the first distillate by steaming I, YI', and this method became the best method for purifying hydrofluoric acid. Recognizing this fact, they completed the present invention.

[Structure and operation of the invention]

The basic structure of the method of the present invention is to first add fluorine to hydrofluoric acid in which the above-mentioned impurities are present and cause a reaction, and then to distill this. By adopting such a configuration, the above-mentioned impurities can be removed with extremely high 6+ efficiency. This is in fact extremely clear from the following experiment conducted by the present inventor H, and the results are shown in Table 2. Of course, these data are subject to change depending on the concentration of each component, temperature, amount of fluorinated IJD, and other conditions, but the strong tendency for impurities to concentrate in the first distillate and reduce the amount of water is not completely explained. remained unchanged throughout the experiment.

Table 2 However, in Table 2 above, 70 ppm of fluorine was added to hydrofluoric acid containing certain impurities (containing 0.01% water) before distillation, and the mixture was heated at 10 to 15°C for 30 minutes. This figure shows the results of distillation after the reaction. For comparison, the results obtained in the same manner without adding any fluorine are also shown. As is clear from Table 2 above, it can be seen that hydrofluoric acid can be purified to an extremely high purity by adding fluorine.

The first possible reason for the remarkable effects of fluorine addition is that its fundamental effect is to forcibly transform impurities into low-boiling-point fluorine compounds due to its strong reactivity. It is considered deaf. For example, sulfur compounds are concentrated in the first distillate when SO, f', S
This is because it changes into a compound with an extremely low boiling point, such as OF, in a very short time.

The second possible effect of fluorine addition treatment is that its strong oxidation +sh hydraulic power removes coexisting moisture, etc., and also removes impurities such as those shown in (a) to (i) above. The goal is to thoroughly resolve the complex equilibrium relationship between the two countries. For example, fluorine reacts instantaneously with water and converts into OF2.0□, OF2.01, etc., which are all low boiling point gases and can be easily removed from the system. This leaves no obstacles to distillation and purification.

When carrying out the present invention, first, the above-mentioned impurities are present.・F: Yuzu. ', Containing impurities at the edge of the mountain Y1. Although there are no special restrictions, the O2 concentration is usually 11% or less in impure anastomoses. It is of course possible to use hydrohydric acid, which has been purified in advance to remove impurities to some extent, in cases where the invention has not yet been made.

The impurities contained in this case are expressed as 1t1 and 5.Not only in each form, but also in any form, it can be the object of the purification method of the present invention, and it is certain that the impurity is high. Can be removed at level. In this case, the hydrofluoric acid is one that contains at least 3% or less water and 7% or less of water in the hydrofluoric acid.

The operation of adding fluorine to hydrofluoric acid may be performed before or during distillation. in this case,
Fluorine is introduced into the reaction system as fluorine gas, as a mixed fluorine gas with an inert gas, or in the form of a solution of fluorine gas dissolved in an inert liquid such as hydrofluoric acid. The reaction between impurities and fluorine gas is -40~+40℃
(Under reduced pressure, normal pressure.

under pressure), preferably between -20 and
It is convenient to carry out at +20°C and normal pressure, and -20'
When the temperature is higher than C, a reaction to fluorinate impurities starts simultaneously with the addition of fluorine gas, and the higher the temperature, the faster this reaction progresses.

Next, in the present invention, distillation is essential. The method for this distillation is not particularly limited5, and any of a variety of fumigation methods can be used effectively in a wide range, and preferred specific examples include the batch type Naru purification method and the continuous Handome purification method. be done.

〔Example〕

The inventors conducted numerous experiments and completed the present invention.
The superiority of the present invention has been confirmed, and several representative examples will be extracted as examples and shown below. Therefore, the present invention is not limited to the embodiments described below, and it goes without saying that the embodiments may be modified and implemented as desired without departing from the spirit and gist of the present invention. The hydrofluoric acid raw material used in the following examples contains at least the impurities shown in Table 1.

Example 1 A container made of polychloro-1-lifluoroethylene equipped with a reflux condenser and a distillation tube (hydrogen fluoride FD 80 per capacity)
0gr and fluorine gas (Fz 98.6%.

1.4%) was blown into a cylinder at room temperature to a concentration of 80 ppm based on the raw material, and then the container was heated for rectification. After removing the initial distillate, The fraction (bp, 20°C) is collected as the main fraction.

This purified hydrofluoric acid contained only the following star impurities and was truly suitable as hydrofluoric acid for electronic materials.

RSi PO4SO-CI Example 2 Using the same equipment as Example 1, 800 g of hydrofluoric acid was added to the container.
After pouring 0.4 gr of fluorine gas (F289.8%, HF 10.2%) generated from the F-7 electrolytic tank as F, and melting it at -10℃, the container was heated. One distillation of hydrofluoric acid was carried out to obtain purified hydrofluoric acid. The amount of impurities in this purified hydrofluoric acid was measured and found to be as follows.

B Si POa 5OaCI Example 3 A Seiko S1 apparatus that can be operated continuously and has a cooler and a packed tower made of polytetrafluoroethylene is used. A thin pipe for introducing fluorine gas from a fluorine electrolytic cell (20 J) was connected to a continuous supply section provided at the bottom of the apparatus to feed raw material hydrofluoric acid into this apparatus. Fluorine gas (F288.6%,
HF (11.4%) was continuously blown into the raw material hydrofluoric acid from the gas supply port so that the amount of fluorine was 1100 pp, heated to around 20° C., and rectified. The light WI fraction is extracted from the distillation pipe at the top of the rectification column, and the
Distill and collect hydrofluoric acid from distillation tube No. 3. The amount of impurities in the purified hydrofluoric acid obtained after 10 hours of continuous operation was measured as follows.

lλ Si POa 504C1 [Effects of the Invention] The method for purifying hydrofluoric acid using fluorine is truly an epoch-making invention in that it reduces the content of impurities from the conventional ppm level to the ppb level. The development has made it possible to fully meet the demands of various industrial fields that handle electronic materials and fine chemicals that require ultra-high purity hydrofluoric acid, and also for research applications that value precision in various areas of cutting-edge technology. It has become possible to meet the expectations of consumers as materials such as It has also become possible to synthesize ultra-high purity fluorine compounds using this hydrofluoric acid as a raw material.

Claims (1)

[Claims] (1) Fluorine is added to hydrofluoric acid in which a compound of at least one nonmetallic element selected from the group consisting of boron, silicon, phosphorus, sulfur, and chlorine is dissolved, reacted, and then purified by distillation. A method for purifying hydrofluoric acid characterized by the following.