CN1327032C - F2 gas generating device, F2 gas generating method and F2 gas - Google Patents

Abstract

The invention is to electrolyze an electrolyte (24) composed of KF.2HF to generate high-purity F₂F of gas₂Gas (es)The generator is characterized by comprising a production system (A) for producing KF.2 HF from KF or KF.HF, an HF supply system (B) for supplying HF to the electrolyte (24) and the production system (A), and a generator for generating F by electrolyzing the KF.2 HF produced by the production system (A)₂A gas generating system (C).

Description

F2 gas generating device, F2 gas generating method and F2 gas

technical field

The invention relates to an _F2 gas generating device, a _F2 gas generating method and _F2 gas. In particular, it relates to _{a F2} gas generating device and a _F2 gas generating method for generating high-purity F2 gas with very few impurities used in manufacturing processes of semiconductors and the like, and _F2 gas produced by these methods and devices.

Background technique

F ₂ gas is used, for example, as an indispensable main gas in the field of semiconductor manufacturing. However, it is sometimes used alone. Recently, nitrogen trifluoride gas (hereinafter referred to as NF ₃ gas) and the like are synthesized from F ₂ gas as a raw material, and this gas is used as a cleaning gas for semiconductors or a gas for dry etching. In addition, neon fluoride gas (hereinafter referred to as NeF gas), argon fluoride gas (hereinafter referred to as ArF gas), and krypton fluoride gas (hereinafter referred to as KrF gas) are excimer laser oscillations used in semiconductor integrated circuit drawing. Most of the raw materials are mixed gases of rare gases and _F2 gases.

In an electrolytic cell containing a predetermined amount of electrolyte composed of KF·HF, carbon is used as the anode and nickel is used as the cathode to perform electrolysis to generate this _F2 gas. In general, KF·HF charged into the electrolytic cell is initially charged with a predetermined amount of KF·HF, and then HF is appropriately supplied to be used as KF·2HF. At this time, KF·HF of the insufficient part was injected, and KF·2HF was formed by supplying HF again, and a predetermined amount of electrolytic solution was prepared. KF, which is an electrolyte component, has high hygroscopicity, and generally contains moisture when building an electrolytic bath. The inventor first applied for a high-purity fluorine generator with few impurities (WO01/77412A1).

However, the _F2 gas generated in this way contains 45 to 55% of oxygen in the _F2 gas generated initially. Usually, the generated F ₂ gas reacts with water contained in the electrolytic solution as represented by the following formula (1), thereby reducing the amount of oxygen contained in the F ₂ gas. However, it is difficult to make the amount 3000 ppm or less.

2F ₂ +H ₂ O→F ₂ O+2HF...(1)

The aforementioned excimer laser oscillation gas or the surface treatment of the excimer laser stepper lens (CaF ₂ single crystal) requires high-purity F ₂ gas. The oxygen concentration contained in the _F2 gas is required to be 1000 ppm or less for the former excimer laser oscillation gas, and 500 ppm or less for the surface treatment gas of the latter excimer laser stepper lens ( _CaF2 single crystal).

Contents of the invention

An object of the present invention is to provide _an F 2 gas generator capable of stably generating high-purity F ₂ gas with a very low oxygen content, a F ₂ gas generating method, and high-purity F ₂ gas.

The _F2 gas generator of the present invention that solves the aforementioned problems is to electrolyze the electrolytic solution composed of KF·2HF to generate high-purity _{F2 gas} . A production system for KF·2HF, an HF supply system for supplying HF to the electrolytic solution and the preparation system, and a _F2 gas generation system for electrolyzing KF·2HF prepared by the above production system to generate _F2 gas.

After preparing KF·2HF from KF or KF·HF in a closed preparation system, the prepared KF·2HF is put into an electrolytic cell closedly connected with the preparation system. Therefore, the KF·2HF put into the electrolytic cell does not absorb water, that is, an electrolytic solution with a low oxygen content can be formed. Therefore, the amount of oxygen contained in the _F2 gas obtained by electrolysis of the electrolytic solution can be very small from the initial stage of generation.

In addition, the F ₂ gas generator of the present invention is characterized in that a moisture removal mechanism for removing moisture in the aforementioned KF or KF·HF is attached to the aforementioned preparation system.

The amount of oxygen can be reliably reduced when preparing KF·2HF from KF or KF·HF.

In addition, in the F ₂ gas generator of the present invention, the oxygen concentration in the generated F ₂ gas is 2% or less.

The oxygen concentration in the _F2 gas is reduced to 2% or less, preferably 0.2% or less (2000ppm or less), more preferably 0.02% or less (200ppm or less). Therefore, it can be used as a gas for excimer laser oscillation, or a gas for surface treatment of an excimer laser stepper lens (CaF ₂ single crystal).

In addition, the _F2 gas generating device of the present invention is an F2 gas generating device that electrolyzes an electrolytic solution composed of KF· _2HF to generate _F2 gas, and is characterized in that it has a KF·2HF prepared from KF or KF·HF The preparation system, and the HF supply system for supplying HF to the aforementioned electrolytic solution and the aforementioned preparation system, and the _F2 gas generation system for electrolyzing KF·2HF prepared by the aforementioned preparation system to generate _F gas, are provided with the adjustment of the aforementioned preparation system, Moisture control mechanism for moisture in each system of the HF supply system and _F2 gas generation system or the overall external atmosphere of each system.

Oxygen incorporation can be reliably suppressed because a moisture control mechanism is provided to adjust moisture in each system of the aforementioned preparation system, HF supply system, and _F2 gas generation system or in the overall external atmosphere of each system.

In addition, in the F ₂ gas generator of the present invention, the aforementioned moisture control mechanism is a casing that can control the internal atmosphere of each of the aforementioned systems or the entirety of each of the systems.

Since the moisture control mechanism is a casing that can control the atmosphere, it is easy to adjust the humidity of each system or the overall atmosphere of each system. Therefore, the incorporation of oxygen can be reliably suppressed.

In addition, the _F2 gas generation method of the present invention is the F2 gas generation method that electrolyzes the electrolytic solution composed of KF·2HF to generate _F2 gas, and is equipped with a _moisture removal mechanism for removing moisture in KF or KF·HF 1. In the preparation system for preparing KF or KF·HF into KF·2HF, after the aforementioned KF or KF·HF is heated and degassed under a vacuum or inert gas atmosphere for a given period of time, in a vacuum or an inert gas atmosphere After cooling to room temperature, supply HF of the HF supply system gas to the preparation system, react the aforementioned KF or KF·HF with the aforementioned HF in the aforementioned manufacturing system to generate KF·2HF, and supply the KF·2HF to _F2 gas After the generation of the electrolyzer, the method of electrolyzing the _F2 gas that generates low-concentration oxygen is carried out.

With such a configuration, the oxygen concentration of the generated _F2 gas can be reduced, and it can be used as a gas for excimer laser oscillation or a surface treatment gas for an excimer laser stepper lens ( _CaF2 single crystal).

In addition, the _F2 gas generation method of the present invention is a method of removing the adsorption water and crystallization water of the aforementioned KF or KF·HF by heating the aforementioned KF or KF·HF in the aforementioned production system at 200-300°C.

In this way, moisture in KF or KF·HF can be reliably removed. Therefore, oxygen contained in water can be removed, and the oxygen concentration in the generated F ₂ gas can be reliably reduced from the initial stage of F ₂ gas generation.

In addition, the _F2 gas of the present invention is in a preparation system that is equipped with a moisture removal mechanism for removing moisture in KF or KF·HF, and prepares KF or KF·HF into KF·2HF in a predetermined time, vacuum or inert After heating and degassing the above-mentioned KF or KF·HF in a gas atmosphere, cool to room temperature in a vacuum or an inert gas atmosphere, and then supply HF gasified from the HF supply system to the production system. Inside, the aforementioned KF or KF·HF is reacted with the aforementioned HF to generate KF·2HF, and this KF·2HF is supplied to the electrolyzer of the F ₂ gas generation system, and electrolyzed to generate gas. Therefore, since it is a high-purity _F2 gas with an extremely low oxygen concentration, it can be used as various main gases for semiconductor manufacturing. On the other hand, the F ₂ gas of the present invention has an oxygen concentration of 2% or less.

The oxygen concentration in the F ₂ gas is preferably reduced to 0.2% or less (2000 ppm or less), more preferably 0.02% or less (200 ppm or less). Therefore, it can be used as a gas for excimer laser oscillation, or a gas for surface treatment of an excimer laser stepper lens (CaF ₂ single crystal).

Description of drawings

Fig. 1 is a schematic view of the fluorine gas generator of the present invention.

Fig. 2 is a graph showing the relationship between the amount of energization and the amount of O ₂ in F ₂ gas in Example 1 and Comparative Examples 1 and 3.

Detailed ways

Hereinafter, an example of an embodiment of the present invention will be described with reference to FIG. 1 .

The _F2 gas generating device G in this embodiment is a device that electrolyzes the electrolytic solution 24 composed of KF·2HF to generate high-purity _F2 gas, and has a preparation system A that prepares KF or KF·HF into KF·2HF , HF supply system B for supplying HF to electrolytic solution 24 _{and production system A, and F 2 gas generation system C for electrolyzing KF·2HF produced in production system A to generate F 2 gas} .

In Fig. 1, KF or KF·HF is prepared into the preparation system A of KF·2HF, the KF·2HF preparation device 7 that is made of the Ni container 7a that holds KF10 and the loam cake 7b that seals this container 7a, and covers this The container 7a of the KF·2HF preparation device 7, the heater 9 for heating the KF10 inside, the cooling water pipe 8 for cooling, the vacuum piping 2 connected to the vacuum exhaust system D provided on the upper cover 7b, The piping 3 for inert gas purge and the HF supply and KF·2HF sending piping 1 inserted into the KF10 and connected to the HF supply system B and the F ₂ gas generation system c are constituted.

In the HF supply system B that supplies HF to this production system, the HF gas cylinder 11 mounted on the load cell 12 is installed in the sleeve 13 . This sleeve 13 is connected to a propylene scrubber not shown. The surface of the HF gas cylinder 11 is covered with a heater 14 to keep the inside of the HF gas cylinder 11 at a predetermined temperature. In addition, the gas volume in the HF gas cylinder 11 is measured by the load cell 12, and the supply volume of HF gas to the production system A and the _F2 gas generation system C is measured. This HF cylinder 11 is connected to the production system A through the piping 5 for sending out HF.

The _F2 gas generating system C is composed of an electrolytic solution 24 composed of a KF·2HF mixed molten salt, an electrolytic tank 20 containing the electrolytic solution 24, and an anode 22 and a cathode 22 for electrolyzing the electrolytic solution 24 as main components.

The electrolytic cell 20 is integrally formed using metal such as Ni, monel, pure iron, and stainless steel. An anode chamber 28 and a cathode chamber 29 are partitioned by a partition wall 2 made of nickel or monel. An anode 22 made of low polarizability carbon is arranged in the anode chamber 28 , and a cathode 23 made of Ni or Fe is arranged in the cathode chamber 29 . A discharge port 25 for F ₂ gas generated from the anode chamber 28 and a cathode chamber 29 and a discharge port 26 for H ₂ gas generated from the cathode chamber 7 are arranged on the upper cover 30 of the electrolytic cell 20 . In addition, the electrolytic cell 20 is provided with a heater 31 for heating the inside of the electrolytic cell 20 . In addition, an unillustrated heat insulating material is provided around the heater 31 . The heater 31 is a belt type or a nickel-chromium heating wire, and its shape is not particularly limited, but it is preferably a shape that covers the entire circumference of the electrolytic cell 20 .

The vacuum exhaust system D is composed of a molecular sieve 16 and a vacuum pump 17 . In addition, when the KF10 accommodated in the production system A is heated by the heater 9, moisture desorbed from the KF10 is attracted.

Hereinafter, the operation of the F ₂ gas generator G configured as above will be described.

Firstly, after the preparation system A is heat-treated at 250-300° C. with the heater 9 , a predetermined amount of KF10 is filled in the container 7 a. Then, reheat to 250-300°C under vacuum or purging of ultra-high-purity inert gas, and keep it for 24-48 hours to dry KF10. At this time, the vacuum piping valve 2a is opened, the valve 3a and the valve 4b are closed, and the vacuum exhaust system D is used to exhaust the inside of the container 7b. In this way, the KF10 is heated to 250-300°C under the purge of ultra-high-purity inert gas, and the adsorption water and crystal water in KF10 can be removed by heat treatment for 24-48 hours.

The results of KF's thermogravimetry (Thermogravimetry, hereinafter referred to as TG) and differential thermal analysis (Differential Thermal Analysis, hereinafter referred to as DTA). Endothermic peaks at 43.4°C, 64.4°C, 90.8°C and 151.6°C were observed. Among them, the endothermic peaks at 43.4°C, 64.4°C, and 90.8°C are the peaks of adsorbed water, and the peak at 151.6°C is the peak of desorption of crystal water. It is estimated that the adsorbed water which is the raw material KF is easily decomposed by the reaction represented by the above-mentioned formula (1). However, the water of crystallization corresponding to the endothermic peak at 151.6°C of DTA has a strong interaction with KF and the HF mainly contained in the electrolyte forms a network due to hydrogen bonds, so it is estimated that the water of crystallization will be very small if it becomes a small amount. Difficult to spread, or difficult to exclude. Therefore, as mentioned above, the crystal water can be desorbed by heating KF to 250-300° C. under purging of ultra-high-purity inert gas, and heat treatment for 24-48 hours, preferably 10-30 hours.

Thereafter, after cooling to room temperature, valve 2a was closed, valve 4b and valve 3a were opened. At this time, the high-purity inert gas piping 4 is preheated to 30 to 35° C. with the line heater 15 . Then, the heater 14 is used to heat the HF cylinder 11 to vaporize the HF, and when the valve 5 is opened, the HF is slowly introduced into the KF10 of the production system A. At this time, the reaction between KF10 and HF is intense, and water is passed into the cooling water pipe 8 for heat release to cool the KF·2HF preparation device 7 to prevent the temperature from rising above 100°C. Because the temperature exceeds 100°C, and when the temperature reaches 200°C, a violent reaction of HF is generated, showing a state similar to an explosion.

In this way, when HF is introduced into the production system A, the molar ratio of HF in KF10 to KF·HF can be increased to increase the supply rate of HF. Then, after confirming that a predetermined amount of HF has been supplied to the preparation system A by using the load cell 12 of the HF supply system B, the valve 5a is closed and the valve 4a is opened to introduce high-purity inert gas from the pipe 1, and the pipe 3 for purging the inert gas is carried out. exhaust. This is to prevent the HF in the pipe 1 from being rapidly absorbed into the KF·2HF10 prepared as KF·2HF to cause backflow solidification into the KF·2HF pipe 1 .

Then, after purging the inside of the preparation system A with an inert gas for an appropriate time, the valve 4b is closed. Next, an inert gas is supplied from the pipe 3 for inert gas purge. Simultaneously, valve 18 and valve 19 are opened. The preparation system A uses the gas pressure of the inert gas introduced from the inert gas purging pipe 3 to send the prepared KF·2HF through the pipe 1 to the electrolytic cell 20 of the _F2 gas generation system C. At this time, the electrolytic cell 20 is previously heat-treated at 250 to 300° C. to desorb adsorbed water and the like.

Like this, F of _the present invention The gas generating device can make the high-purity KF 2HF with little moisture adsorption amount not contact with the air and be supplied to the F in the electrolytic cell of the gas generating device, and high-purity KF _can be formed in the electrolytic cell. Electrolytic bath KF·2HF. Therefore, the oxygen concentration of the electrolytic solution is extremely low.

In addition, each system of the adjustment system A, the HF supply system B, and the F ₂ gas generation system C may be separately housed in a housing capable of controlling the atmosphere. Therefore, the humidity of the atmosphere outside each system can be adjusted, and the incorporation of oxygen into each system can be suppressed. In addition, the entirety of each system, that is, the F ₂ gas generator G may be housed in one housing. Furthermore, by installing all of these systems in a clean room, the same effect as housing them in a basket (frame) capable of controlling the atmosphere can be obtained. In this way, by suppressing the incorporation of oxygen into each system, the oxygen concentration in the generated _F2 gas can be reduced more reliably.

In addition, the F ₂ gas generating device and the F ₂ gas generating method of the present invention are not limited to the aforementioned embodiments.

(Example)

Hereinafter, the F ₂ gas generator of the present invention will be specifically described by way of examples.

(Example 1)

In the _F2 gas generator G shown in Fig. 1, firstly, the adjustment system A is heat-treated at 250-300°C by using the heater 9, and then KF10 is filled in the container 7a, and the high-purity _N2 gas with a purity of 99.9999% is blown Sweep it down and heat it to 250-300°C, and keep it for 24-48 hours to dry KF10. Then, cool to room temperature, and introduce HF into KF10 of preparation system A. At this time, water was passed through the pipe 8 for cooling water, and the KF·2HF production apparatus 7 was cooled so that the temperature was 100° C. or lower. Then, after confirming that a predetermined amount of HF has been supplied to the production system A by using the load cell 12 of the HF supply system B, the inside of the production system A is purged with high-purity _N gas for an appropriate time, and then high-purity _N gas is supplied. , using the N ₂ gas pressure to send the prepared KF·2HF from the pipe 1 to the electrolytic cell 20 of the F ₂ gas generation system C to form an electrolyte solution with an electrolyte volume of 71. Then, in the F ₂ gas generation system C, a carbon electrode was used for the anode and a Ni electrode was used for the cathode, and galvanostatic electrolysis was performed at an applied current density of 10 A/dm ² . Then, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography at about 100Ahr energization time, and it was about 650ppm.

(Example 2)

Using the same KF 2HF as in Example 1 as the electrolyte, in the _F2 gas generating system C, the anode uses a carbon electrode and the cathode uses a Ni electrode, and constant current electrolysis is carried out at an applied current density of 15A/ ^dm2 . Then, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography at about 100Ahr energization time, and it was about 950ppm.

(Example 3)

Using the same KF·2HF as in Example 1 as the electrolyte, in the _F2 gas generation system, the anode uses a carbon electrode and the cathode uses a Ni electrode, and carries out constant current electrolysis at an applied current density of 2A/ ^dm2 . Then, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography at about 100Ahr energization time, and it was about 450ppm.

(Example 4)

Using the same KF·2HF as in Example 1 as the electrolyte, the F ₂ gas generating system C is housed in an unshown casing as a moisture control mechanism, and the humidity inside the casing is controlled at 40%. The anode uses a carbon electrode, A Ni electrode was used as the cathode, and constant current electrolysis was performed at an applied current density of 20A/dm ² . Then, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography at about 100Ahr energization time, and it was about 70ppm.

(comparative example 1)

The KF·2HF prepared by the conventional method was used in the electrolyte, and in the _F2 gas generation system C, a carbon electrode was used for the anode and a Ni electrode was used for the cathode, and constant current electrolysis was performed at an applied current density of 10A/ ^dm2 . Then, when the amount of energization was about 100Ahr, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography, and the result was about 30000ppm.

(comparative example 2)

The KF·2HF prepared by the conventional method was used in the electrolyte. In the _F2 gas generation system C, a carbon electrode was used for the anode and a Ni electrode was used for the cathode. Constant current electrolysis was performed at an applied current density of 15A/ ^dm2 . Then, when the amount of energization was about 100Ahr, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography, and the result was about 25000ppm.

(comparative example 3)

Using the same KF 2HF as the electrolyte in the _F2 gas generation system C, the anode uses a carbon electrode and the cathode uses a Ni electrode, and constant current electrolysis is performed at an applied current density of 1A/ ^dm2 . Then, when the amount of energization was about 100Ahr, the amount of O ₂ in the generated F ₂ gas was measured by gas chromatography, and it was about 21000ppm.

FIG. 2 shows the relationship between the current flow amount and the O ₂ amount in the F ₂ gas in the case of the aforementioned Example 1 and Comparative Examples 1 and 3.

As shown in Fig. 2, after drying KF and desorbing moisture, the result of Example 1 in which the material for preparing KF·2HF is used in the electrolyte solution shows that the amount of oxygen in _F2 gas is small from the initial stage of _F2 gas generation.

Industrial availability

The present invention uses KF·2HF after drying the KF, desorbing the adsorbed water or crystal water on the surface through the above-mentioned _structure , and can stably generate _F2 gas containing very low oxygen concentration from the initial stage of F2 gas generation.

Claims (7)

1. _F2 gas generating device is an _F2 gas generating device that electrolyzes an electrolyte composed of KF·2HF to generate _F2 gas, and is characterized in that it has a preparation system that prepares KF or KF·HF into KF·2HF , and an HF supply system for supplying HF to the electrolytic solution and the production system, and an F _{2 gas generation system for electrolyzing KF·2HF produced by the production system to generate F 2 gas} . 2. The _F2 gas generating device according to claim 1, wherein a water removal mechanism for removing water in the KF or KF·HF is attached to the preparation system. 3. The _F2 gas generator according to claim 1, wherein the oxygen concentration in the generated _F2 gas is 2% or less. 4. The _F2 gas generator is a F2 gas generator that electrolyzes the electrolyte composed of KF·2HF to generate _{F2 gas} , It is characterized in that it has a production system for producing KF 2HF from KF or KF HF, an HF supply system for supplying HF to the electrolytic solution and the production system, and electrolyzes KF 2HF produced by the production system. _F2 gas generating system that generates _F2 gas, Attached is a moisture control mechanism to adjust the moisture in the external atmosphere of each of the aforementioned preparation system, HF supply system, and _F2 gas generation system or the entirety of each system. 5. The _F2 gas generating device according to claim 4, wherein the moisture control mechanism is a casing capable of controlling the internal atmosphere of each of the systems or the whole of the systems. 6. The _F2 gas generation method is a F2 gas generation method _in which _F2 gas is generated by electrolyzing an electrolyte solution composed of KF·2HF, In the preparation system of preparing KF 2HF from KF or KF HF equipped with a moisture removal mechanism for removing moisture in KF or KF HF, the aforementioned KF or KF HF is mixed in a vacuum or an inert gas atmosphere for a predetermined time. After heating and degassing, cool to room temperature under vacuum or an inert gas atmosphere, and then supply gas-phased HF from the HF supply system to the production system, and combine the aforementioned KF or KF·HF with the aforementioned HF reacts to generate KF·2HF, and after supplying the KF·2HF to the electrolytic tank of the _F2 gas generation system, electrolysis is performed to generate _F2 gas with low oxygen concentration. 7. The method for generating _F2 gas according to claim 6, characterized in that, in the aforementioned preparation system, the aforementioned KF or KF·HF is heated at 200-300°C to remove the adsorbed water and crystallization of the aforementioned KF or KF·HF water.

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