KR20050005541A - Method for producing highly pure anhydrous solutions containing hydrogen fluoride - Google Patents

Abstract

Hydrogen fluoride is added to at least one anhydrous solvent, wherein the hydrogen fluoride is added to the anhydrous solvent or solvents in the form of a gas and / or a liquefied gas or a mixture of gas and liquefied gas. A method of preparing a high purity solution containing fluoride, one or more salts thereof, or a mixture of two or more thereof is provided. Also disclosed are high purity hydrogen fluoride and ammonium fluoride solutions prepared by the present invention.

Description

METHOD FOR PRODUCING HIGHLY PURE ANHYDROUS SOLUTIONS CONTAINING HYDROGEN FLUORIDE}

In particular, the electronics and semiconductor industries require high purity process solutions. There is a need for solutions containing HF, HF salts, or mixtures thereof, with or without other components in such solutions.

In particular, ammonium fluoride solutions in which the highest purity requirements are imposed are generally prepared by dissolving crystalline ammonium fluoride in a corresponding solvent, as described, for example, in US Pat. No. 5,320,709. One drawback of this method is that the metallic impurities are generally in the ppm range and the solution is therefore unsuitable for applications with stricter purity requirements for metal content. However, further purification of the crystalline ammonium fluoride required to prepare a high purity solution with substantially lower metal content is difficult.

Another drawback is that it is difficult to obtain reproducible concentrations of free hydrogen fluoride from batch to batch in the ammonium fluoride solution during manufacture. However, in some industrial applications constant free hydrogen fluoride content is important.

There is still a need for solutions of hydrogen fluoride and hydrogen fluoride salts with better purity and solutions of hydrogen fluoride salts where the concentration of free hydrogen fluoride remains relatively constant from batch to batch.

The present invention relates to a process for producing a high purity solution containing hydrogen fluoride (HF), salts thereof or mixtures thereof, wherein the hydrogen fluoride is introduced into anhydrous solvent as a gas and / or a liquefied gas.

This need is in accordance with the present invention. The present invention provides a process by which hydrogen fluoride and solutions of these salts can be prepared to have unprecedented levels of purity.

Thus, according to one aspect of the invention, a hydrogen fluoride is passed into at least one anhydrous solvent, wherein the hydrogen fluoride is introduced into the anhydrous solvent or solvents as a gas and / or a liquefied gas. A method of preparing a high purity solution containing fluoride or one or more salts thereof alone or in combination is provided.

Any anhydrous solvent in which hydrogen fluoride can be dissolved may be used as the anhydrous solvent. In general, they are polar anhydrous solvents. Thus, the present invention encompasses the process as described above, wherein at least one anhydrous solvent in the process is a polar solvent.

The invention also provides an embodiment wherein a high purity water solution is prepared, wherein at least one other component is additionally used in the hydrogen fluoride and anhydrous solvent or solvents.

Thus, the present invention also provides for the introduction of 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 or solvents in addition to the hydrogen fluoride. To a method as described above.

In a preferred embodiment of the process of the invention, ammonia is a component additionally used for hydrogen fluoride, whereby an ammonium fluoride solution is prepared.

Accordingly, the present invention also relates to a process for preparing a high purity ammonium fluoride solution as described above wherein ammonia is used as an additional component in the process. It is possible in principle to use liquid ammonia, but gaseous ammonia is preferred.

In another preferred embodiment of the process of the invention, the additional component is another gas used as the reactive gas in etching. Examples are hydrogen chloride and hydrogen bromide.

The present invention therefore also relates to the process as described above, in which the gaseous hydrogen chloride or gaseous hydrogen bromide or mixtures thereof are used as additional components. In the process according to the invention, the stoichiometric ratio of hydrogen fluoride to hydrogen chloride and / or hydrogen bromide is preferably below 1, more preferably below 1.

The invention also comprises one or more salts thereof, such as hydrogen fluoride or ammonium fluoride, alone or in combination, and optionally contains additional components prepared according to the methods as described above.

Hydrogen fluoride is added to anhydrous solvents or solvents in an anhydrous gas and / or a liquefied gas by essentially conventional means. In a preferred embodiment, the anhydrous solvent or solvents are placed in a suitable container. The container material may consist essentially of any material that is suitable for contact with the hydrogen fluoride and free of impurities to ensure high purity of the resulting solution. The container having an inner wall in contact with the high purity solution is preferably made of metal-free polymers such as HDPE, PFA, polypropylene, PVDF, and perfluorinated polyethylene propylene (FEP).

Unstable HD-polyethylene, such as HD-polyethylene having a specific density of 0.940-0.970 g / cm 3, in particular 0.942-0.961 g / cm 3, is a suitable polymer among them. This includes polyethylene designated by the trademarks Lupolen®, such as Lupolen® 6021D, Lupolen® 5021D, Lupolen® 4261AQ149 and Lupolen® 4261AQ135. The container used in the method of the present invention may consist of one or more layers, wherein one or more outer layers which are not in contact with the solution may consist essentially of any material.

The line carrying the hydrogen fluoride as a gas and / or liquefied gas into a vessel in which anhydrous solvent or solvents are disposed may also consist essentially of any material. Bonding hoses consisting of high purity PFA are preferably used in the present invention.

The gaseous hydrogen fluoride must be liquefied according to the process of the invention before being added to an anhydrous solvent or solvents, which can be carried out essentially by any conventional means.

If the hydrogen fluoride is added to the anhydrous solvent or solvents in the form of a liquefied gas as well as in the form of a gas according to the method of the present invention, first the gaseous hydrogen fluoride is introduced and then the liquefied hydrogen fluoride is introduced. It is possible to introduce. It is also possible to introduce liquefied hydrogen fluoride first and then to hydrogen fluoride in gaseous form. It is also possible to introduce gaseous and liquefied hydrogen fluorides simultaneously, where gaseous and liquefied hydrogen fluorides can be mixed prior to introduction.

According to the process of the invention, it is possible to bring the hydrogen fluoride introduced into the anhydrous solvent or solvents into the gas and / or the liquefied gas to a predetermined temperature prior to introduction. It is also possible to bring the anhydrous solvent or solvents to a predetermined temperature prior to introduction. The solution may also be made to lead to a predetermined temperature or to maintain the predetermined temperature during the introduction of the hydrogen fluoride into anhydrous solvent or solvents. Temperature control can be carried out by essentially conventional means.

During the addition of the hydrogen fluoride in anhydrous solvents or solvents, it is possible to essentially homogenize the solution by conventional techniques. In a preferred embodiment of the invention, the solution is recycled through one or more pump-overs after completion of the hydrogen fluoride addition.

In a preferred embodiment of the invention, the anhydrous solvent or solvents are selected from polyols, carboxylic acids, carboxylic acid derivatives, organic sulfur compounds, aliphatic or aromatic nitrogen compounds, and mixtures of two or more thereof.

Examples of the polyols include ethylene glycol, propylene glycol, polymethylene glycol, polyethylene glycol and glycerol. Particular preference is given to polyols having a relatively low viscosity. Preference is also given to polyalkylene glycols, in particular polyethylene glycols having a number-average molecular weight of 250-6,000, more preferably of a molecular weight of 250-5,000, in particular of 250-1,000.

The carboxylic acid includes aliphatic, cycloaliphatic and aromatic acids that are liquid at ambient conditions, and may have one or more acid groups. Examples thereof include formic acid, acetic acid and propionic acid. Acid derivatives of carboxylic acids such as their esters or their amides are also suitable solvents. It is also possible to use acrylic derivative carboxylic acids or carboxylic acid derivatives. Hydroxyl groups and halogens are included as possible substituents. Amino carboxylic acids are also included as possible solvents.

Anhydrous organic sulfur compounds such as sulfates, sulfonates, sulfoxides, sulfones or sulfites are also suitable solvents, which are 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-butane dibis (methane sulfonate) , Diethyl sulfate, dipropyl sulfate, dibutyl sulfate, dihexyl sulfate, dioctyl sulfate and the like.

In addition, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate are also suitable anhydrous solvents for use in the process of the present invention.

Anhydrous aliphatic compounds substituted so that the hydrogen fluoride can be dissolved can also be used as the solvent. Halogen substituents are mentioned as possible substituents.

Other groups of possible solvents are aliphatic and aromatic amines, which may be substituted with amino alcohols, for example ethanolamine.

According to the process of the invention, the hydrogen fluoride may first be introduced into an anhydrous solvent or part of the solvents, after which another solvent may be added.

When two or more different anhydrous solvents are used in the process of the invention, the hydrogen fluoride may be added first to one or more of these solvents, and then one or more other solvents may be added to the resulting mixture. . It is also possible to prepare two or more hydrogen fluoride solutions in the same manner as described above and subsequently to mix the two or more solutions.

If the additional components or components do not react with the hydrogen fluoride, the order of introduction is not important. The additional component or components may be introduced into the solution of hydrogen fluoride in anhydrous solvent. It is also possible to first mix the additional components or components with anhydrous solvents or solvents and then add hydrogen fluoride. In addition, it is possible to introduce additional components or components together with hydrogen fluoride into anhydrous solvents or solvents. If desired, the hydrogen fluoride may be mixed with at least one additional ingredient before being added to the anhydrous solvent or solvents, and the resulting mixture may then be added to the anhydrous solvent or solvents.

If the additional component is ammonia, the anhydrous solvent or solvents may be contacted with the desired amount of gaseous hydrogen fluoride, after which a corresponding amount of gaseous ammonia is added. It is also possible to contact the solvent or solvents with the desired amount of gaseous ammonia and then introduce a corresponding amount of gaseous hydrogen fluoride. Two gaseous components may also be introduced into the solvent or solvents simultaneously and in spatial separation. It is also possible to introduce one of the two gaseous components and then start the introduction of the remaining gaseous components after a certain time.

In a particularly preferred embodiment of the process of the invention, the anhydrous solvent or solvents are first treated with the desired amount of gaseous hydrogen fluoride and the solvent is recycled as described above. The gaseous ammonia is then introduced into this homogenized solution and the resulting solution is in turn recycled by pumping over and homogenized accordingly.

The temperature in the reaction vessel is controlled to not exceed at most 35 ° C, preferably at most 30 ° C, and particularly preferably below 30 ° C, during the introduction of gaseous ammonia.

The concentration of the high purity solution of ammonia fluoride prepared according to the process of the present invention depends essentially on the solubility of ammonium fluoride in the solvent or solvents and can be at any level within this range. It is also possible to prepare a saturated solution of ammonium fluoride in the solvent or solvents, and it is also possible for this amount of ammonia and hydrogen fluoride to be introduced in which the ammonium fluoride precipitate is present as a solid.

In a preferred embodiment of the invention, a high purity solution of ammonium fluoride is prepared in the solvent or solvents according to the process of the invention, the concentration of which is generally 0.1-50% by weight, preferably 1-30% by weight, Especially preferably, it is 2.5-10 weight%.

In order to avoid the production of explosive ammonia-air mixtures, an inert atmosphere can be used in and around the vessel, where gaseous ammonia is added to an anhydrous solution or solutions in which hydrogen fluoride has already been dissolved. Essentially any inert gas such as nitrogen or argon is suitable. Preferably, the vessel atmosphere is inert before being filled with solvent and, if desired, hydrogen fluoride.

In principle, all of the above solvents can be used as the solvent from which ammonium fluoride is prepared. In a preferred embodiment, anhydrous polyols are used, in particular preferred anhydrous ethylene glycol.

The present invention also provides a process which allows the production of high purity ammonium fluorides having a constant content of free hydrogen fluoride which can be set reproducibly. The content of free hydrogen fluoride contained in the high purity ammonium fluoride solution prepared according to the present invention can be set by simple stoichiometric addition of gaseous hydrogen fluoride and gaseous ammonia into the solvent or solvents. . The precise measurements allowed by the use of gaseous components allow the preparation of high purity solutions with precisely defined amounts of free hydrogen fluoride that can be accurately regenerated. In particular, high purity solutions of ammonium fluoride may be prepared to have less than 0.01% by weight of free hydrogen fluoride.

Hydrogen fluoride solution prepared by the process of the invention is used in the etching process. The method of the present invention can be used to produce a solution that conforms to the etch process purity requirements. The process of the invention can also be used to prepare solutions with hydrogen fluorides having previously known concentrations. Preferred solutions according to the invention contain about 10-35% by weight of hydrogen fluoride.

In principle, the anhydrous solvent can be used in this embodiment of the process according to the invention, provided that the additional gaseous component or components are soluble in the solvent or solvents. In a preferred embodiment, acetic acid or a mixture of acetic acid and acetic ester, or a mixture of DMSO and DMA is used as the anhydrous solvent. If a mixture of DMSO and DMA is used, the stoichiometric mixing ratio of DMSO and DMA is in the range of about 30:70 to 70:30. In a particularly preferred embodiment of the invention, a high purity solution of hydrogen fluoride is prepared in a DMSO / DMA mixture, where the hydrogen fluoride, DMSO, and DMA have the same parts by weight.

If the additional component is another reactive gas used for etching, such as hydrogen chloride or hydrogen bromide, the order in which the gas is added to the anhydrous solvent or solvents is not critical. It is also possible to add these gases into anhydrous solvents or solvents continuously or simultaneously and spatially separately or together in one feeder as needed. Other gaseous constituents or components are liquefied and the liquefied gases or gases are anhydrous solvents or solvents prior to addition into the anhydrous solvents or solvents according to conventional techniques, such as as described above for the introduction of hydrogen fluoride. It is also possible to introduce into the field.

It is also possible to introduce gaseous hydrogen chloride and / or gaseous hydrogen bromide into anhydrous solvents or solvents in addition to gaseous hydrogen fluoride and gaseous ammonia in accordance with the process of the invention. The order of introducing each component is not limited in principle.

In addition to the gaseous hydrogen fluoride, the high purity solution or the field of use of the present invention in which at least one additional reactive gas is also used as one component is not limited to the above-mentioned etching.

The term "purity" as used herein relates to all possible impurities that a solution prepared according to the invention may have. Among them, metal ions, other anions such as halogenides such as chloride or bromide, nitrates, phosphates or sulfates, organic compounds, and generally certain impurities, viruses, bacteria, and their by-products such as endotoxins or mycotoxins are all possible It is included as an impurity.

The term "high purity" as used herein refers to the degree of purity associated with a particular impurity in the range of less than 1 ppb.

According to the method of the present invention a high purity solution of high purity can be prepared in relation to all possible impurities. In a preferred embodiment of the process of the invention, the high purity solution is prepared with very low content of metal ions.

According to the method of the present invention, for all possible impurities, a component with an impurity level so low that a high purity solution can be prepared without further purification steps and with the purity required by the user is used.

Depending on the degree of purity required for the high purity solution to be prepared, it is possible with the method of the invention to use a high purity hydrogen fluoride gas and / or one or more high purity solvents. If at least one additional component is used as described above, this component may also be of high purity.

With regard to the preparation of high purity solutions with very low contents of metal ions as described above, the process according to the invention uses gaseous hydrogen fluorides having a metal ion content of less than 1 ppb, preferably less than 100 ppt.

Examples of metals in connection with the high purity of the solution prepared according to the invention are aluminum, antimony, arscenic, 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, zinc, tin or zirconium.

Depending on the required purity of the solution to be prepared, it is possible, if necessary, to lower the impurity content of the anhydrous solvent or solvents so that the range is less than 1 ppb, preferably less than 100 ppt, according to conventional conventional methods. Specifically, distillation methods can be used to purify the anhydrous solvent or solvents, such as by means of general distillation or by distillation using microwave radiation.

Thus, the process of the present invention also provides a high purity solution having a metal-ion content of less than 100 ppt per metal. The high purity solutions prepared according to the invention can be used in all possible applications where a solution consisting of hydrogen fluoride or one or more salts alone or in combination thereof is used. More specifically, applications are found in the semiconductor and electronics industries, as well as in analytical chemistry (bio) pharmaceuticals.

High purity solutions prepared according to the process of the invention are particularly suitable for use as etchant. The hydrogen fluoride content of the high purity ammonium fluoride solution of the present invention can be continuously recycled during manufacture. This can provide an extremely narrow process window for the etch rate of the solution.

In particular, the high purity solution prepared according to the method of the present invention is used as an etchant for selectively removing organometallic residue or organic silicon residue in the plasma etching method of wafer fabrication. In connection with this selectivity, the process of the present invention can be particularly useful for controlling the etch selectivity of a solution among other properties by the addition of additional reactive gases such as hydrogen chloride or hydrogen bromide as described above.

In another embodiment of the method of the present invention, water may be mixed into a high purity solution to adjust the etching selectivity. A significant advantage of the process of the present invention is that the high purity solution is anhydrous. For example, a high purity ammonium fluoride solution can be prepared using gaseous hydrogen fluoride, gaseous ammonia and anhydrous solvents, thus providing a very precise and reproducible water content by the addition of water after the preparation of the high purity solution. Can be set.

It is also possible to prepare anhydrous high purity solution of the present invention and then add an aqueous solution of additional components to the solution. The advantage is that the water content of the solution to be prepared can be set precisely and on the basis of the anhydrous solution in a single step, which also leads to one or more additional components. Examples include aqueous acids such as phosphoric acid, aqueous hydrochloric acid, or aqueous acetic acid.

In a particularly preferred embodiment of the invention, at least one substance is added to the anhydrous solvent as an additional component that affects the surface activity properties of the high purity solution used as the etchant. Non-polar materials as well as appropriate polarity can be used here. Examples include aliphatic amines or aromatic amines. Aliphatic amines having a chain length of 5-12 carbon atoms are preferably used. The amine may be substituted for the purpose of solubility, if necessary, where a OH group or a halogenide residue is possible.

In order to achieve the required purity of the high purity solution, it is necessary to purify the material which affects the surface activity before use. Here, essentially any suitable conventional prior art method can be used.

The non-limiting examples shown below illustrate certain aspects of the invention. All parts and percentages are by weight unless otherwise indicated and all temperatures are in degrees Celsius.

Example 1 Preparation of Hydrogen Fluoride Solution in Ethylene Glycol

800 g of ethylene glycol is placed in a 1,000 ml batch vessel. Using an injector, about 80 g of anhydrous hydrogen fluoride was concentrated and dissolved in ethylene glycol. Here, the increase in the content of hydrogen fluoride was monitored analytically. The addition of the liquid acid was terminated at a content of 10% by weight.

After termination, the solution was recycled and homogenized for 1 hour by means of a pump-over line. The solution had a metal-ion content of less than 100 ppt per metal.

Example 2: Preparation of Ammonium Fluoride Solution in Ethylene Glycol

Nitrogen was blanketed in a 1,000 ml batch vessel for 1 hour. Subsequently, the process of Example 1 was repeated to obtain a HF solution dissolved in ethylene.

Gaseous ammonia was introduced into this HF solution dissolved in ethylene, where the molar ratio of ammonia and hydrogen fluoride was 1: 1. The temperature was controlled not to exceed 30 ° C by external cooling and ammonia addition rate control.

After introducing the total amount of ammonia, the solution was recycled for 30 minutes while cooling. The resulting solution had a metal-ion content of less than 100 ppt per metal.

Example 3-6

In Example 3, Example 1 was repeated replacing ethylene glycol with glacial acetic acid. In Example 4, glacial acetic acid was used again as a solvent in a 90:10 weight ratio relative to HF (720 g of glacial acetic acid, 80 g of HF). Examples 5 and 6 were repeated with Example 4 using 80:20 and 70:30 weight ratios of glacial acetic acid to HF (glacial acetic acid 640 g and HF 160 g, respectively) and glacial acetic acid 560 g and HF 240 g).

The description of the above embodiments and preferred embodiments is exemplary and not intended to limit the invention as defined by the claims. It will be readily appreciated that various modifications and combinations of the above features may be utilized without departing from the invention as set forth in the claims. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications are intended to be included within the scope of the following claims.

Claims (14)

Adding hydrogen fluoride to at least one anhydrous solvent, wherein the hydrogen fluoride is about 10-35% by weight of the anhydrous solvent or in the form of a gas or a liquefied gas or a mixture of gas and a liquefied gas A method of making a high purity solution containing hydrogen fluoride, one or more salts thereof, or a mixture of two or more thereof, added to solvents. 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 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 at least one anhydrous solvent is acetic acid. The method of claim 1 wherein at least one additional gas or at least one additional liquid or at least one additional solid or a mixture of two or more thereof is used as an additional component to the hydrogen fluoride. A process according to claim 5, wherein gaseous ammonia is used as an additional component. The method of claim 6, wherein the at least one anhydrous solvent is DMA, DMSO, or mixtures thereof. 6. The process according to claim 5, wherein gaseous hydrogen chloride or gaseous hydrogen bromide or mixtures thereof are used as additional components or components. The method of claim 1 wherein the hydrogen fluoride is used having a metal-ion content of less than 1 ppb per metal. The method of claim 1 wherein the solution has a metal-ion content of less than 100 ppt per metal. A high purity solution comprising about 10-35% by weight of hydrogen fluoride in at least one anhydrous solvent. 12. The solution of claim 11 wherein said solvent is acetic acid. 12. The solution of claim 11 wherein the solution has a metal-ion content of less than 100 ppt per metal. 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.