JP2005528316A - Method for producing high purity non-aqueous solution containing hydrogen fluoride - Google Patents

Abstract

  A method for producing a high purity solution containing hydrogen fluoride, one or more salts thereof, or a mixture of two or more thereof by adding hydrogen fluoride to at least one anhydrous solvent, wherein hydrogen fluoride is a gas , Liquefied gas, or a mixture of gas and liquefied gas, added to anhydrous solvent (s). High purity hydrogen fluoride solutions and ammonium fluoride solutions produced by the method of the present invention are also disclosed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly pure solution containing hydrogen fluoride (HF), a salt thereof, or a mixture thereof, in which hydrogen fluoride is an anhydrous solvent as a gas and / or liquefied gas. To be introduced.

  Among other things, the electronics and semiconductor industries require high purity process solutions. Among these solutions, what is needed is a solution containing HF, HF salt, or a mixture thereof (with or without other components).

  Ammonium fluoride solutions with the highest purity requirements are generally produced by dissolving crystalline ammonium fluoride in the corresponding solution as described in US-A-5,320,709. One of the disadvantages of this method is that metal impurities are generally in the ppm region and are therefore unsuitable for fields of use that require stringent purity with respect to metal content. However, it is difficult to further purify crystalline ammonium fluoride in order to produce a high purity solution with a fairly low metal content.

  A further disadvantage is that in production it is very difficult to obtain free hydrogen fluoride in ammonium fluoride solution at a reproducible concentration between batches. However, in some industrial applications, free hydrogen fluoride that is constant is important.

  There remains a need for high purity hydrogen fluoride and hydrogen fluoride solutions and hydrogen fluoride salt solutions in which the concentration of free hydrogen fluoride is relatively constant from batch to batch.

SUMMARY OF THE INVENTION This need is met by the present invention. The present invention provides a method by which a solution of hydrogen fluoride and its salts can be produced with a level of purity not previously obtained.

  Accordingly, one aspect of the invention provides a method for producing a high purity solution containing hydrogen fluoride or one or more salts thereof, alone or in combination, wherein the method comprises at least one hydrogen fluoride. By passing through an anhydrous solvent, hydrogen fluoride is introduced into the anhydrous solvent (s) as a gas and / or liquefied gas.

  Any anhydrous solvent in which hydrogen fluoride is soluble can be used as the anhydrous solvent. In general, these are polar anhydrous solvents. Accordingly, the present invention includes the above methods wherein the at least one anhydrous solvent is a polar solvent.

The invention also includes embodiments in which high purity solutions are produced in which at least one other component is used in addition to hydrogen fluoride and anhydrous solvent (s).
Accordingly, the present invention introduces, in addition to hydrogen fluoride, at least one other gas or at least one other liquid or at least one solid or a mixture of two or more thereof into the anhydrous solvent (s) Also related to the method.

In a preferred aspect of this embodiment of the invention, ammonia is a component used in addition to hydrogen fluoride, thereby producing an ammonium fluoride solution.
Thus, the present invention also relates to a method for producing the above-described high-purity ammonium fluoride in which ammonia is used as an additional component. In principle, liquid ammonia can be used, but ammonia gas is preferred.

  In another preferred aspect of this embodiment of the method of the present invention, the additional component is another gas used as a reactive gas in etching. Among these, hydrogen chloride and hydrogen bromide are mentioned as examples.

  Accordingly, the present invention also relates to the above method wherein hydrogen chloride gas, hydrogen bromide gas, or a combination thereof is used as an additional component. In the method of the present invention, the stoichiometric ratio of hydrogen fluoride: hydrogen chloride and / or hydrogen bromide is preferably 1 or less, more preferably less than 1.

  The present invention also includes a high purity solution of hydrogen fluoride or one or more salts thereof (eg, ammonium fluoride, which may be used alone or in combination) produced by the above method, the high purity solution being added These components are optionally contained.

  Hydrogen fluoride is added to the aqueous solution (s) in the absence of water as anhydrous gas and / or liquefied gas by essentially conventional means. In a preferred embodiment, the anhydrous solvent (s) is placed in a suitable container. The container material may be made of essentially any material that is suitable for contact with hydrogen fluoride and free of impurities to ensure high purity of the product solution. The container has an inner wall that contacts the high purity solution, and the inner wall is preferably made of a metal free polymer such as HDPE, PFA, polypropylene, PVDF, perfluoropolyethylenepropylene (FEP).

Among the polymers, unstabilized HD-polyethylene, for example, HD-polyethylene having a specific gravity of 0.940-0.970 g / cm ³ , particularly 0.942-0.961 g / cm ³ is suitable. This includes polyethylene sold under the trade name Lupolen® (eg, Lupolen® 6021D, Lupolen® 5021D, Lupolen® 4261AQ149, Lupolen® 4261AQ135). The container used in the method of the present invention may consist of one or more layers, and the one or more outer layers that are not in contact with the solution can be made of essentially any material.

  The line that transports hydrogen fluoride as a gas and / or liquefied gas to the vessel can be filled with anhydrous solvent (s), and the line can also consist essentially of any suitable material. A hose coupling made of high purity PFA is preferably used in the method of the present invention.

If the hydrogen fluoride gas is liquefied by the method of the present invention before being added to the anhydrous solvent (s), the liquefaction can be performed by essentially any conventional means.
When hydrogen fluoride is added to the aqueous solution (s) in gaseous and liquefied gas form by the method of the present invention, gaseous hydrogen fluoride and liquefied hydrogen fluoride may be added first. it can. It is also possible to add liquefied hydrogen fluoride first and then gaseous hydrogen fluoride. Furthermore, gaseous hydrogen fluoride and liquefied hydrogen fluoride can be introduced simultaneously, and gaseous and liquefied hydrogen fluoride may be mixed before introduction.

  In the method of the present invention, hydrogen fluoride introduced into the anhydrous solvent (s) as gas and / or liquefied gas can be brought to a predetermined temperature before introduction. Anhydrous solvent (s) can be brought to a predetermined temperature prior to introduction. While introducing hydrogen fluoride into the anhydrous solvent (s), the solution may be at a predetermined temperature and / or maintained at a predetermined temperature. The temperature adjustment can be carried out by essentially conventional means.

  During the addition of hydrogen fluoride to the anhydrous solvent (s), the solution can be homogenized by essentially conventional techniques. In a preferred embodiment of the invention, after the conversion of hydrogen fluoride is complete, it is recycled at one or more pump-over lines.

  In a preferred embodiment of the method of the present invention, the anhydrous solvent (s) is selected from polyols, carboxylic acids, carboxylic acid derivatives, organic sulfur compounds, aliphatic or aromatic nitrogen compounds, and mixtures of two or more thereof.

  Among them, examples of the polyol include ethylene glycol, propylene glycol, polymethylene glycol, polyethylene glycol, and glycerol. A polyol having a relatively low viscosity is particularly preferred. Further preferred are polyalkylene glycols, especially polyethylene glycols having a number average molecular weight of 250 to 6000, more preferably having a number average molecular weight of 250 to 5,000, especially 250 to 1,000.

  Carboxylic acids include aliphatic, cycloaliphatic, and aromatic acids that are liquid at ambient conditions and may have one or more acid groups. Examples include formic acid, acetic acid, and propionic acid. Acid derivatives of carboxylic acids, such as their esters or amides, are also suitable solvents. Furthermore, acrylic derivatives, carboxylic acids, or carboxylic acid derivatives can also be used. Possible substituents include hydroxyl groups and halogens. Possible solvents also include aminocarboxylic acids.

Anhydrous organic sulfur compounds such as sulfate, sulfonate, sulfoxide, sulfone are also suitable solvents, DMSO, dimethyl sulfite, diethyl sulfite, glycol sulfite, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dibutyl sulfone, tetramethylene sulfone. , Methyl sulfolane, diethyl sulfoxide, dipropyl sulfoxide, dibutyl sulfoxide, tetramethylene sulfoxide, ethyl methane sulfonate, 1,4-butanediol bis (methane sulfonate), diethyl sulfate, dipropyl sulfate, dibutyl sulfate, dihexyl sulfate, dioctyl In addition, sulfates, etc. are included, ethylene carbonate, propylene carbonate, dimethyl carbonate, die Tyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate are also suitable anhydrous solvents used in the process of the present invention.

An anhydrous aliphatic compound substituted so that hydrogen fluoride is soluble can also be used as a solvent. Among these, halogen substituents can be said to be possible substituents.
Another group of possible solvents are aliphatic and aromatic amines, for example substituted amino alcohols such as ethanolamine.

According to the method of the present invention, hydrogen fluoride may be first added to some anhydrous solvent (s) and then further solvent may be added after introduction.
If two or more different anhydrous solvents are used in the process of the present invention, hydrogen fluoride may be added first to these one or more solvents and the resulting mixture may be added to one or more other solvents. Two or more solvents of hydrogen fluoride may be prepared by the method described above, followed by mixing the two or more solutions.

  If the additional component (s) do not react with hydrogen fluoride, the order of introduction is not critical. Additional component (s) may be introduced into an anhydrous solvent solution of hydrogen fluoride. It is also possible to first combine the anhydrous solvent (s) with the additional component (s) and add hydrogen fluoride. In addition, the additional component (s) can be introduced into the anhydrous solvent (s) along with hydrogen fluoride. In addition, additional component (s) can be introduced together with hydrogen fluoride into the anhydrous solvent (s). If necessary, mix hydrogen fluoride with at least one additional component (s) before adding to anhydrous solvent (s) and add the resulting mixture to anhydrous solvent (s) can do.

  If the additional component is ammonia, the anhydrous solvent (s) may be contacted with the desired amount of hydrogen fluoride gas, followed by the corresponding amount of ammonia gas. First, the anhydrous solvent (s) may be contacted with the desired amount of ammonia gas, followed by the corresponding amount of hydrogen fluoride gas. The two gas components may be introduced into the solvent (s) simultaneously and spatially separately. One of the two gas components may be introduced, and the introduction of the other gas component may be started after a certain time.

  In a particularly preferred embodiment of the invention, the anhydrous solvent (s) is first treated with the desired amount of hydrogen fluoride gas and the solvent is recycled as described above. Ammonia gas is then introduced into the homogenized solution, and the resulting solution is then recirculated with a pump and homogenized.

The temperature of the reaction vessel is controlled to be at most 35 ° C., preferably at most 30 ° C., particularly preferably less than 30 ° C. during the introduction of ammonia gas.
The concentration of the high purity solution of ammonium fluoride produced by the method of the present invention depends essentially only on the concentration of ammonium fluoride in the solvent (s) and can be at any level within this framework. . A saturated solution of ammonium fluoride in the solvent (s) can also be produced, and amounts of ammonia and hydrogen fluoride can be introduced such that the ammonium fluoride precipitates as a solid.

  In a preferred embodiment of the present invention, the method of the present invention produces a high purity solution of ammonium fluoride in the solvent (s), generally at a concentration of 0.1 to 50 wt%, preferably 1 to 30 wt%. %, Particularly preferably in the range of 2.5 to 10% by weight.

  In order to avoid the formation of an explosive ammonia-air mixture, an inert atmosphere may be used in and around the container, the ammonia gas being added to the aqueous solution (s) without hydrogen fluoride in the solution. Already dissolved. Essentially any inert gas, such as nitrogen or argon among others, is suitable. The container atmosphere is preferably deactivated before being filled with the solvent and, if necessary, hydrogen fluoride.

  In principle, all of the above solvents can be used as solvents in which ammonium fluoride is produced. In a preferred embodiment, anhydrous polyol is used, and in a particularly preferred embodiment, anhydrous ethylene glycol is used.

  The present invention also provides a method that allows the production of a high purity ammonium fluoride solution having a certain amount of free hydrogen fluoride set with good reproducibility. The content of free hydrogen fluoride contained in the high-purity ammonium fluoride solution produced by the method of the present invention is obtained by simply adding hydrogen fluoride gas and ammonia gas in equivalent amounts to the solvent (s). Can be set. The use of gas components allows for accurate measurements, thereby producing a high purity solution having a precisely defined content of free hydrogen fluoride that is accurately reproduced. In particular, it is possible to produce a high purity ammonium fluoride solution having less than 0.01% by weight of free hydrogen fluoride.

  The hydrogen fluoride solution prepared by the method of the present invention is used for an etching process. The method of the present invention can be used to prepare solutions that meet the purity requirements of the etching process. The method of the present invention can also be used to produce a solution having a concentration of hydrogen fluoride not previously known. Preferred solutions according to the present invention contain about 10 to about 35% by weight hydrogen fluoride.

  In principle, all of the aforementioned anhydrous solvents can be used in this aspect of the process of the invention, as long as the additional gas component (s) is soluble in the aforementioned anhydrous solvent (s). . In a preferred embodiment, acetic acid or a mixture of acetic acid and acetate, or a mixture of DMSO and DMA is used as the anhydrous solvent. When a mixture of DMSO and DMA is used, the DMSO and DMA stoichiometric mixing ratio is in the range of about 30:70 to about 70:30. In a particularly preferred embodiment of the present invention, a high purity hydrogen fluoride solution is produced in a DMSO / DMA mixture, where hydrogen fluoride, DMSO, and DMA are in the same weight proportions.

  If the additional component is another reaction gas (eg, hydrogen chloride or hydrogen bromide) used in the etch, the order in which the gases are added to the anhydrous solvent (s) is not critical. The gas may be added sequentially or simultaneously to the anhydrous solvent (s), and may be added spatially separated to one feeder, if necessary, or together. In addition, the other gas component (s) may be liquefied and added to the liquefied prior to addition to the anhydrous solvent (s) by conventional techniques (eg, the method described above for the introduction of hydrogen fluoride). The gas (s) can be introduced into the anhydrous solvent (s).

  According to the method of the present invention, hydrogen chloride gas and / or hydrogen bromide gas can be introduced into the anhydrous solvent (s) in addition to hydrogen fluoride gas and ammonia gas. The order in which the individual components are introduced is not limited in principle.

  In the field relating to the use of high-purity solutions, or in the field of the present invention, in addition to hydrogen fluoride gas, at least one further reaction gas is also used as a component, but the field is not limited to the etching described above.

  As used herein, the phrase “purity” relates to all possible impurities that a solution made according to the present invention may have. Among them, metal ions, halides (eg chloride or bromide), further anions (eg nitrate ion, phosphate ion, sulfate ion), organic compounds, broadly specific impurities, viruses, bacteria, and their By-products (eg endotoxin or mycotoxin) are all included in the possible impurities.

As used herein, the term “highly pure” refers to a degree of purity with respect to certain impurities and is in the range of less than 1 ppb.
High purity solutions can be made by the method of the present invention which is high purity with respect to all possible impurities. In a preferred embodiment of the method of the present invention, a very high purity solution with a very low content of metal ions is made.

  In the method of the present invention, since the impurity concentration is low with respect to all the possible impurities in the components used, a very high-purity solution having the purity required by the user is prepared without further purification steps. be able to.

  Depending on the degree of purity required for the high purity solution produced, high purity hydrogen fluoride gas and / or one or more high purity solvents can be used by the method of the present invention. If at least one of the aforementioned additional ingredients is used, this ingredient can also be of high purity.

  As described above, with respect to the production of high purity solutions having a very low content of metal ions, the method of the invention uses hydrogen fluoride gas, a metal ion content of less than 1 ppb, preferably less than 100 ppt.

  For high purity solutions made according to the present invention, examples of metals include, among others, aluminum, antimony, arsenic, barium, beryllium, lead, cadmium, calcium, chromium, iron, gallium, germanium, gold, indium, potassium, cobalt, Copper, lithium, magnesium, manganese, molybdenum, sodium, nickel, platinum, silver, silicon, strontium, thallium, titanium, vanadium, bismuth, zinc, tin, or zirconium.

  Depending on the purity required of the solution to be prepared, the impurity content of the anhydrous solvent (s) will be in the range of less than 1 ppb, preferably in the range of less than 100 ppt, if necessary, by conventional conventional methods. Can be reduced. In particular, the anhydrous solvent (s) can be purified using distillation methods, for example by conventional distillation or distillation using microwave irradiation.

  Accordingly, the present invention also provides a high purity solution having a metal ion content of less than 100 ppt per metal. In all possible applications where hydrogen fluoride or one or more salts thereof are used alone or in combination, very high purity solutions made in accordance with the present invention can be used. In particular, applications are found in the field of semiconductors, the electronics industry, analytical chemistry and (bio) medicine.

  High purity solutions made by the method of the present invention are particularly well suited for use as an etching gas. The fact that the hydrogen fluoride content of the high purity ammonium fluoride solution of the present invention can be reproduced consistently in production is particularly advantageous. This can provide an extremely narrow process window for the etch rate of the solution.

  In particular, the high-purity solution prepared by the method of the present invention is used as an etching agent for selectively removing organometallic residues or organosilicon residues in a plasma etching method for producing a wafer. With regard to this selectivity, the method of the present invention can be used particularly advantageously to control the etch selectivity of the solution by the addition of additional reaction gases (eg, hydrogen chloride and hydrogen bromide as described above).

  In another aspect of the invention, water can be mixed into the high purity solution to modify the etch selectivity. A considerable advantage of the present invention is that the high-purity solution is anhydrous, for example, a high-purity ammonium fluoride solution can be produced using hydrogen fluoride gas, ammonia gas, and an anhydrous solvent to produce a high-purity solution. By adding water later, the water content can be set very accurately and with good reproducibility.

  It is also possible to add an additional component aqueous liquid to the solution after preparing the anhydrous high purity solution of the present invention. Among other things, it is advantageous that the water content of the solution to be produced can be accurately set in a single step that also introduces one or more additional components, based on a non-aqueous solution. Examples thereof may be, inter alia, other aqueous acids such as phosphoric acid, aqueous hydrochloric acid, or acetic acid solution.

  In a particularly preferred embodiment of the invention, at least one substance is added as an additional component to the anhydrous solvent, among which substances that affect the surface-active properties of the high purity solution used as the etchant are added. Here, suitable polar and non-polar materials can be used. Among them, examples are aliphatic or aromatic amines. An aliphatic amine having a chain length of 5 to 12 carbon atoms is preferably used. If necessary for solubility purposes, the amine may be substituted, among which OH groups or halogenide residues are possible substituents.

  In order to obtain the purity required for high purity solutions, it may be necessary to purify substances that affect the surface activity before use. Here, essentially any suitable and conventional prior art method can be used.

  The following non-limiting examples illustrate certain aspects of the present invention. Unless otherwise noted, all parts and percentages are by weight and all temperatures are in degrees Celsius.

Example 1 Preparation of an ethylene glycol solution of hydrogen fluoride 800 g of ethylene glycol was placed in a 1000 ml batch container. About 80 g of anhydrous hydrogen fluoride was condensed with an injector and dissolved in ethylene glycol. In it, the increase in the content of hydrogen fluoride was monitored analytically. The liquid acid addition was stopped at a content of 10% by weight.

After stopping, the solution was recirculated for 1 hour by a pump-over line and homogenized. The solution had a metal ion content of less than 100 ppt per metal.
Example 2 Preparation of ethylene glycol solution of ammonium fluoride A 1000 ml batch vessel was blanketed with nitrogen for 1 hour. Then, the procedure similar to Example 1 was repeated and the ethylene glycol solution of HF was obtained.

  Ammonia gas was introduced into the ethylene glycol solution of HF, where the molar ratio of ammonia: hydrogen fluoride was 1: 1. The temperature was controlled by external cooling and control of the ammonia addition rate so that the temperature did not exceed 30 ° C.

After introducing the total amount of ammonia, the solution was recirculated with cooling for 30 minutes. In the resulting solution, the metal ion content per metal was less than 100 ppt.
Example 3-6
In Example 3, Example 1 was repeated replacing ethylene glycol with glacial acetic acid. In Example 4, glacial acetic acid was again used as the solvent and the glacial acetic acid: HF weight ratio was 90:10 (720 g glacial acetic acid, 80 g HF). Examples 5 and 6 were repeated with Example 4 using glacial acetic acid: HF weight ratios of 80:20 and 70:30 (640 g glacial acetic acid and 160 g HF, respectively; 560 g glacial acetic acid, 240 g HF).

  The foregoing description of the embodiments and preferred embodiments should be taken as illustrative rather than limiting on the present invention as defined by the claims. As will be readily appreciated, many variations and combinations of the features set forth above may be used without departing from the present invention as set forth in the claims. Such modifications are not to be regarded as a departure from the spirit and script of the invention, and all such modifications are intended to be within the scope of the following claims.

Claims (14)

Adding hydrogen fluoride to at least one anhydrous solvent, wherein from about 10 to about 35 wt% hydrogen fluoride is added in the form of a gas or liquefied gas or a mixture of gas and liquefied gas in an anhydrous solvent ( Singular or plural)
A method for producing a high-purity solution containing hydrogen fluoride, one or more salts thereof, or a mixture of two or more thereof.   The method of claim 1, wherein the at least one anhydrous solvent is a polar solvent.   The method of claim 1, wherein the at least one anhydrous solvent is selected from the group consisting of polyols, carboxylic acids, carboxylic acid derivatives, organic sulfur compounds, aliphatic or aromatic nitrogen compounds, and mixtures of two or more thereof.   4. The method of claim 3, wherein the at least one anhydrous solvent is acetic acid.   2. The method of claim 1, wherein in addition to hydrogen fluoride, at least one additional gas, at least one additional liquid, at least one additional solid, or a mixture of two or more thereof is used as a component.   6. The method of claim 5, wherein ammonia gas is used as an additional component.   The method of claim 6, wherein the at least one anhydrous solvent is DMA, DMSO, or a mixture thereof.   6. The method of claim 5, wherein hydrogen chloride gas, hydrogen bromide gas, or mixtures thereof are used as additional component (s).   The process of claim 1 wherein hydrogen fluoride is used at a metal ion content of less than 1 ppb per metal.   The method of claim 1, wherein the solution is used at a metal ion content of less than 100 ppt per metal.   A high purity solution comprising from about 10 to about 35 weight percent hydrogen fluoride in at least one anhydrous solvent.   12. The solution of claim 11, wherein the solvent is acetic acid.   12. The solution of claim 11, wherein the solution has a metal ion content per metal of less than 100 ppt.   12. The solution of claim 11, further comprising one or more components selected from the group consisting of water, ammonium fluoride, hydrogen chloride, and hydrogen bromide.