Patent Application
20190047858
The present invention relates to a purification method for purifying a fluorine gas by removing a metal component from a fluorine gas that contains a metal component as an impurity.
A fluorine gas has been widely used in etching of substrate and cleaning gas of a thin film formation device such as CVD (Chemical Vapor Deposition), in manufacturing steps for semiconductor devices, MEMS (Micro Electro Mechanical Systems) devices. TFT (Thin Film Transistor) panels for liquid crystal and solar batteries, or used in fluorinating agents for fluorochemical product synthesis.
In the manufacture of a semiconductor device, due to the improvement of miniaturization and high integration technology, technical difficulty at the time of processing is becoming higher year by year. In such a situation, there is possibility that an impurity contained in a material of the semiconductor device becomes a factor causing a problem of the deterioration of yield of products in the manufacturing step for the semiconductor device. Therefore, also as to a fluorine gas to be used, its high purification is required, and the request level of the purification is extremely high. In particular, as to a metal impurity which has a large influence on electric characteristics of the semiconductor device largely, for example, it is required to reduce the content of the metal impurity to 10 mass ppb or less such that a fluorine gas has extremely high purity
As a purification method aiming at the high purification of the gas, a cryogenic purification method has been known that is a method in which a mixed gas containing a gas and impurities is cooled to a low temperature and liquefied, and by a difference in a temperature at the time when each of the gases is condensed in the mixed gas, they are separated and recovered by distillation or partial condensation. For example, in a patent document 1, a cryogenic purification method has been disclosed in which an energy is applied to a fluorine compound to react the fluorine compound, thereby generating a fluorine gas component and a gas component other than the fluorine gas component, and furthermore, the fluorine gas component and the gas component other than the fluorine gas component which are generated are cooled by using liquid nitrogen, and a fluorine gas is separated by a difference in the boiling point between both of the gases.
However, the metal impurity contained in the fluorine gas is generally contained as fine grain or cluster of metal or a metal compound, or gas of metal halide or metal complex having a relatively high vapor pressure. However, the sublimation of the metal impurity is extremely high, and moreover, the amount of the metal impurity contained in the fluorine gas is small, and therefore there is a problem that the removal of the metal impurity by the cryogenic purification method is difficult. In addition, when the cryogenic purification method is used, although its equipment is complicated and large, it is possible to install the equipment in a manufacturing factory for the fluorine gas. However, when a small amount of the gas is treated, it is difficult to install the equipment and is therefore unsuitable.
As a method for treating a gas by using a device having a simple structure, a dry type treatment method in which the gas is brought into contact with a solid chemical has been known. For example, in a patent document 2, a method for removing hydrogen fluoride as an impurity by flowing a mixed gas containing a fluorine gas and an impurity through a treating column in a purification device having the treating column filled with adsorbent such as sodium fluoride (NaF) has been known. In addition, a patent document 3 discloses a method for removing sublimated manganese fluoride contained in a fluorine gas produced by heating MnF4. Specifically, it has been described that manganese fluoride and sodium fluoride are brought into contact with each other to react them, and it can be removed by forming compound fluoride with a formula 2NaF+MnF4→Na2MnF6.
The method described in the patent document 2 is an effective method in case where the impurity is hydrogen fluoride. However, the method has almost no effect on impurities other than hydrogen fluoride. In the patent document 2, a method for removing hydrogen fluoride contained in a fluorine gas has been described. However, a removing method in case where impurities are metal impurities is not described. In addition, a fluorine gas generated by general electrolysis of hydrogen fluoride contains approximately 5 mass % of hydrogen fluoride.
In a method described in a patent document 3, it has been disclosed that to form compound fluoride by reacting sodium fluoride and manganese fluoride, they are heated to a high temperature of 100° C. or higher. However, if they are heated to the high temperature, the reaction between a fluorine gas and a metal container filled with the sodium fluoride occurs, and a metal component of the container is mixed to the fluorine gas, and consequently, it becomes a new impurity.
Patent Document 1: Japanese Patent Application Publication 2004-39740
Patent Document 2: Japanese Patent Application Publication 2009-215588
Patent Document 3: Japanese Patent Application Publication 2006-117509
An object of the present invention is to provide a fluorine gas purification method for purifying a fluorine gas by removing a trace metal component which is contained in a fluorine gas as an impurity by a device having a simple structure.
As a result of an eager study to achieve the above object, the present inventors have found that when a trace amount of hydrogen fluoride exists in a fluorine gas containing a metal component as an impurity, the metal component which is contained in the fluorine gas reacts to the hydrogen fluoride and is removed therefrom together with the hydrogen fluoride by being adsorbed to a metal fluoride, and thereby a fluorine gas can be purified, and the present invention is completed.
In the method for purifying the fluorine gas in the present invention, by adding a hydrogen fluoride gas to the fluorine gas to coexist with a hydrogen fluoride gas, it becomes possible to adsorb the metal impurity on the metal fluoride.
That is, the present invention includes inventions 1 to 16.
[Invention 1]
A method for purifying a fluorine gas by removing a metal component from a fluorine gas that contains hydrogen fluoride and the metal component, the method comprising the step of:
removing the hydrogen fluoride and the metal component by bringing the fluorine gas into contact with a solid metal fluoride to adsorb the hydrogen fluoride and the metal component on the metal fluoride,
wherein the content of the hydrogen fluoride in the fluorine gas before the removing step is 50 volume ppm or greater to 1 volume % or less, relative to a total volume of the fluorine gas, the hydrogen fluoride and the metal component.
[Invention 2]
The method for purifying the fluorine gas according to the invention 1, wherein before the removing step, a concentration adjusting step is performed for adjusting a content of the hydrogen fluoride contained in the fluorine gas to be 50 volume ppm or greater to 1 volume % or less, relative to a total volume of the fluorine gas, the hydrogen fluoride and the metal component.
[Invention 3]
The method for purifying the fluorine gas according to the invention 1, wherein the concentration adjusting step is an addition step for adding the hydrogen fluoride to the fluorine gas.
[Invention 4]
The method for purifying the fluorine gas according to any one of the inventions 1 to 3, wherein the metal fluoride is at least one kind selected from the group consisting of an alkali metal fluoride and an alkali earth metal fluoride.
[Invention 5]
The method for purifying the fluorine gas according to the invention 4, wherein the metal fluoride is at least one kind selected from the group consisting of lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride and barium fluoride.
[Invention 6]
The method for purifying the fluorine gas according to any one of the inventions 1 to 5, wherein in the removing step, a temperature at a time when the fluorine gas is brought into contact with the solid metal fluoride is 50° C. or lower.
[Invention 7]
The method for purifying the fluorine gas according to any one of the inventions 1 to 6, wherein the metal component contained in the fluorine gas before the removing step contains at least one metal selected from the group consisting of Fe, Cr, Mn, Co, Ti, Mo, Cu and Ni.
[Invention 8]
The method for purifying the fluorine gas according to any one of the inventions 1 to 7, wherein a content of each of Fe, Cr, Mn, Co, Ti, Mo, Cu and Ni contained in the fluorine gas after the removing step is 10 mass ppb or less.
[Invention 9]
A method for purifying a fluorine gas by removing a metal component from a fluorine gas, wherein the fluorine gas contains hydrogen fluoride and at least one metal component selected from the group consisting of Fe, Cr, Mn, Co, Ti, Mo, Cu and Ni, the method comprising the step of:
removing the hydrogen fluoride and the metal component by bringing the fluorine gas into contact with at least one solid metal fluoride selected from the group consisting of lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride and barium fluoride, to adsorb the hydrogen fluoride and the metal component on the metal fluoride,
[Invention 10]
A method for manufacturing a purified fluorine gas by removing a metal component contained in a fluorine gas, comprising the step of:
[Invention 11]
The method for manufacturing the purified fluorine gas according to the invention 10, wherein a content of each of Fe, Cr, Mn, Co, Ti, Mo, Cu and Ni contained in the purified fluorine gas is 10 mass ppb or less.
[Invention 12]
The method for manufacturing the purified fluorine gas according to the invention 10 or the invention 11, wherein a content of the hydrogen fluoride in the purified fluorine gas is 50 volume ppm or less.
[Invention 13]
An etching method, comprising the steps of:
obtaining a purified fluorine gas by applying the method for manufacturing the purified fluorine gas according to the invention 10; and
performing etching of a semiconductor element by using the purified fluorine gas.
[Invention 14]
An etching device, comprising:
a fluorine gas supply unit;
a metal fluoride-filled section in which a fluorine gas supplied from the fluorine gas supply unit is brought into contact with a solid metal fluoride; and
an etching chamber to which an outlet gas of the metal fluoride-filled section is supplied.
[Invention 15]
The etching device according to the invention 14, further comprising a hydrogen fluoride concentration adjusting section provided between the fluorine gas supply unit and the metal fluoride-filled section, wherein the hydrogen fluoride concentration adjusting section is configured to adjust a content of hydrogen fluoride in the fluorine gas to be 50 volume ppm or greater to 1 volume % or less, relative to a total volume of the fluorine gas, the hydrogen fluoride and a metal component.
[Invention 16]
The etching device according to the invention 15, wherein the hydrogen fluoride concentration adjusting section includes a hydrogen fluoride supply section configured to add the hydrogen fluoride to the fluorine gas.
According to the present invention, metal components can be easily removed from a fluorine gas which contains the metal components as impurities by a device having a simple structure, and it is possible to provide a gas which can be used for use in etching and the like, corresponding to miniaturization in a semiconductor field.
In the following, an implementing method of the present invention will be explained in detail with reference to the drawings.
In addition,
<Purification Device 10>
A fluorine gas is supplied to a purification device 10 according to the present invention from a fluorine gas supply unit 20, and the purification device 10 supplies an outlet gas to an external device 30. The purification device 10 is provided with at least a metal fluoride-filled section 100. In addition, it is provided with a hydrogen fluoride concentration adjusting section 110 and a hydrogen fluoride supply section 120 when necessary.
<Metal Fluoride-Filled Section 100>
The metal fluoride-filled section 100 is a container filled with chemicals containing a metal fluoride, and is properly designed considering the purity and the flow velocity of a gas flowing therethrough. For example, an abatement equipment can be used in which a pellet of a metal fluoride is filled on a bottom net, and a treatment object gas is introduced from the lower part and discharged from the upper part. The shape of the chemical filled in the metal fluoride-filled section 100 may be powder, granular or a pellet shape if the metal fluoride is contained. Although the content of the metal fluoride is not also especially limited, the purity of the metal fluoride is generally 90 mass % or greater, preferably 95 mass % or greater. As a metal fluoride to be used, it is possible to cite alkali metal fluorides or alkaline earth metal fluorides, and specifically, as an example, it is possible to cite lithium fluoride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride or barium fluoride. Although these metal fluorides have low reactivity with the hydrogen fluoride, they are preferable because they can adsorb a hydrogen fluoride gas.
In addition, a metal having corrosion resistance to a fluorine compound, fluorine or hydrogen fluoride is used for a material used for the container of the metal fluoride-filled section 100. Specifically, nickel, Hastelloy (registered trademark), Monel (registered trademark) or Inconel (registered trademark) that are nickel-based alloy, aluminum, aluminum alloy or stainless steel can be selected. In addition, as to the stainless steel, there is possibility that Fe or Cr contained in the material reacts to the fluorine compound, and consequently, it becomes a generation source of a metal impurity, and there is therefore necessary to perform a process for forming a passive film on the surface of the container by flowing a fluorine compound gas or a fluorine gas before use.
In addition, the use temperature of the metal fluoride-filled section 100, that is, the temperature at the time when the fluorine gas is brought into contact with the solid metal fluoride is 50° C. or lower. When the use temperature is a temperature lower than the boiling pint of the fluorine gas (−88° C. at one atmospheric pressure) under the pressure inside the metal fluoride-filled section 100, a problem occurs that the gas is condensed inside the metal fluoride-filled section 100, and therefore the use temperature is usually 0° C. or higher. In addition, when the temperature is higher than 50° C., there is possibility that the reaction between the fluorine gas and the container of the metal fluoride-filled section 100 is promoted, and a metal impurity derived from the container is generated, and consequently, the concentration of a metal component increases. It is therefore not preferable. In addition, in case where the metal fluoride-filled section 100 is used at a temperature as low as possible, a higher purification effect can be obtained. However, a cooling equipment is separately requited. In general, it is therefore used at a temperature close to room temperature (approximately 20° C.).
As described below, the fluorine gas supplied to the metal fluoride-filled section 100 preferably contains 50 volume ppm or greater to 1 volume % or less of the hydrogen fluoride. In addition, the content of each metal component (Fe, Cr, Mn, Co, Ti Mo, Cu, Ni) contained in the fluorine gas at the outlet of the metal fluoride-filled section 100 is preferably 10 mass ppb or less so as to be used in a manufacturing step of a semiconductor device.
In addition the content of each of the metal component (Fe, Cr, Mn, Co, Ti, Mo, Cu, Ni) contained in the fluorine gas at the inlet of the metal fluoride-filled section 100 is 10 mass ppb or greater to 1000 mass ppb or less, more preferably 20 mass ppb or greater to 500 mass ppb or less. In case where the amount of the metal components is too large, there is possibility that the metal components cannot be completely removed, and in case where the amount of the metal components is too small, there is no necessity for applying the present invention. Each of the metal components is contained in the gas as fine grain or cluster of metal and metal compounds, or as gas of a metal halide or metal complex having a relatively high vapor pressure. However, the content of each of the metal components is not evaluated as the content of the metal halide or metal complex but is evaluated as the content of a metal simple substance.
The metal components are mixed into the fluorine gas in a state of the above-mentioned metal impurities due to that the metal used as members of a reactor and a pipe, or used as a material used for a cylinder (gas cylinder) in a manufacturing step for the fluorine gas is corroded by the fluorine gas. However, by using the above-mentioned metal having the corrosion resistance to the members and the cylinder, it is possible to suppress the content of the mixed metal components to 1000 mass ppb or less.
In addition, the amount of the hydrogen fluoride contained in the fluorine gas at the outlet of the metal fluorine-filled section 100 is preferably 50 volume ppm or less, relative to the total volume of the fluorine gas, the hydrogen fluoride and the metal components.
<Fluorine Gas Supply Unit 20>
The fluorine gas supply unit 20 corresponds to a storage part of the fluorine gas manufactured by a manufacturing equipment for a fluorine gas and a cylinder filled with the fluorine gas. Although the purity of the gas to be supplied is not limited, in case where a low concentration gas is used, the load of the metal fluoride-filled section 100 arranged on a downstream side becomes large, and the size of the device becomes large and the replacement frequency of the chemical becomes high, and it is therefore preferable to use a gas from which impurities are removed with distillation or a cryogenic purification method in advance. Specifically, the gas of which the purity is 90 volume % or greater is preferably used, and the gas of which the purity is 99 volume % or greater is more preferably used.
<External Device 30>
The external device 30 is connected on the downstream side of the purification device 10. For example, in case where the method of the present invention is used in the manufacturing step of the fluorine gas, the external device 30 corresponds to a filling equipment of the fluorine gas. In addition, in case where the present invention is used for a gas supply line of an etching step, an etching device corresponds to the external device 30. Moreover, one casing can be equipped with both of the purification device 10 and the external device 30.
For example, the purification device 10 of the present invention is provided at a gas receiving port or on the way of a pipe of the etching device, and the outlet gas of the purification device 10 is supplied to an etching chamber, and thereby a semiconductor element can be etched by using the gas from which the metal components are removed.
<Hydrogen Fluoride Concentration Adjusting Section 110>
The hydrogen fluoride concentration adjusting section 110 is configured to adjust the amount of the hydrogen fluoride contained in the fluorine gas supplied to the purification device 10 to an amount suitable for supplying it to the metal fluoride-filled section 100. The content of the hydrogen fluoride in the fluorine gas which is supplied to the metal fluoride-filled section 100 is preferably 50 volume ppm or greater to 1 volume % or less, more preferably 100 volume ppm or greater to 2000 volume ppm or less, relative to the total volume of the fluorine gas, the hydrogen fluoride and the metal components, or it may be 200 volume ppm or greater to 1000 ppm or less, relative to the total volume of the fluorine gas, the hydrogen fluoride and the metal components. When the content of the hydrogen fluoride is less than 50 ppm, it is mostly difficult to reduce the amount of the metal components sufficiently because the amount of the hydrogen fluoride is too small. In case where the fluorine gas supplied from the fluorine gas supply unit 20 has already contained 50 volume ppm or greater of the hydrogen fluoride, it is directly supplied to the metal fluoride-filled section 100. However, in case where the content of the hydrogen fluoride is below 50 volume ppm, it is preferable to supply hydrogen fluoride from the hydrogen fluoride supply section 120.
On the other hand, in case where the content of the hydrogen fluoride exceeds 1 volume %, the chemical of the metal fluoride-filled section 100 needs to be replaced frequently, and it is not economical. In addition to this, there is possibility that the hydrogen fluoride cannot be removed under some condition of the amount of the chemical of the metal fluoride-filled section 100, and the metal components cannot be sufficiently reduced. Therefore, in case where the fluorine gas in which the content of the hydrogen fluoride exceeds 1 volume % is supplied, in the hydrogen fluoride concentration adjusting section 110, it may be diluted by the same kind of a fluorine gas in which the content of the hydrogen fluoride is smaller, or the hydrogen fluoride may be roughly removed by chemicals such as metal fluorides.
<Hydrogen Fluoride Supply Section 120>
The hydrogen fluoride supply section 120 is connected by a pipe on the upstream part of the metal fluoride-filled section 100, and is capable of adding hydrogen fluoride to the fluorine gas. A container and a cylinder (gas cylinder) filled with hydrogen fluoride are connected to the hydrogen fluoride supply section 120. It is preferable to use a high purity hydrogen fluoride which is supplied thereto, and the purity is preferably 99.5 mass % or greater, more preferably 99.9 mass % or greater. Moreover, as to metal impurities, the concentration of each of the metal components of Fe, Cr, Mn, Co, Ti, Mo, Cu and Ni is preferably 10 mass ppb or less.
<Effect of Purification Device 10>
In the purification device 10 using the present invention, the concentration of the metal components can be reduced to an extremely low level by a device having a simple structure in which chemical is simply filled. Therefore, it is possible to obtain a gas with little metal impurities by using the present invention even in a small factory. In addition, since the purification device 10 can be provided immediately before the use of the fluorine gas, the mixing of the metal components derived from a pip and the like can be suppressed, and the external device 30 can use the gas with little metal impurities.
In the following, although the present invention will be specifically explained using an example, the present invention is not limited to the example.
According to the system diagram shown in
Here, the metal components are ones which are mixed in the fluorine gas in the above-mentioned state caused by corrosion of the metal by the fluorine gas, which is used as members of a reactor and a pipe, or used as a material used for a cylinder (gas cylinder) in a manufacturing step for the fluorine gas.
The results of Example and Comparative Example are shown in Table 1.
In Example 1 and Example 2, by bringing the fluorine gas containing a predetermined amount of the hydrogen fluoride into contact with NaF at 25° C., it was possible to reduce the metal concentration. On the other hand, in Comparative Example 1 in which the concentration of the hydrogen fluoride was too low, it was difficult to remove the metal components. In addition, in Comparative Example 2 in which the fluorine gas containing a predetermined amount of the hydrogen fluoride was brought into contact with NaF at 100° C., the metal components cannot be sufficiently removed. This can be assumed that the metal components derived from the metal fluoride-filled section 100 reacted to F2 of a high temperature and were mixed. Moreover, in case of a F2-gas containing 3 volume % of a high concentration HF, the metal concentration was hardly reduced. This can be assumed that the metal components were contained in the outlet gas with HF because HF was not removed completely.
In addition, as shown in Table 2, in Examples 3 to 5 were prepared the same as Example 1 except that the chemical filled in the metal fluoride-filled section 100 was changed to KF-pelet, MgF2-pelet or BaF2-pelet. As a result of this, the removal effect of the metal components was confirmed similar to Example 1.
According to the present invention, it is possible to easily remove metal components contained in a fluorine gas, and a gas which can be used for use in etching and the like corresponding to miniaturization in a semiconductor field can be provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-022455 | Feb 2016 | JP | national |
| 2017-010593 | Jan 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/002854 | 1/27/2017 | WO | 00 |
