Method for removing H2S from a gas composition containing COS and H2S, etching gas, and method for producing an etching gas.

Abstract

This invention provides a method for removing H2S from a gas composition containing COS and H2S without reducing COS. [Solution] A method for removing H2S from a gas composition containing COS and H2S, The process includes an adsorption step in which the gas composition is brought into contact with an adsorbent to adsorb H2S onto the adsorbent, A method for removing H2S, wherein the average pore size of the adsorbent is 3 Å or more and 5 Å or less.

Description

[Technical Field]

[0001] This disclosure relates to a method for removing H2S from a gas composition containing COS and H2S, an etching gas, and a method for producing an etching gas. [Background technology]

[0002] In deep hole processing for 3D NAND flash memory, carbonyl sulfide (COS) is used for etching amorphous carbon masks. With the recent increase in demand for 3D NAND flash memory, stable manufacturing methods for COS are being investigated (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Korean Published Patent No. 10-2024-0013981 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] This disclosure aims to provide a method for removing H2S from a gas composition containing COS and H2S without reducing COS.

[0005] Furthermore, this disclosure aims to provide an etching gas containing COS and H2S suitable for anisotropic processing, and a method for producing the etching gas. [Means for solving the problem]

[0006] This disclosure includes the following components: Item 1. A method for removing H2S from a gas composition containing COS and H2S, The process includes an adsorption step in which the gas composition is brought into contact with an adsorbent to adsorb H2S onto the adsorbent, A method for removing H₂S, wherein the adsorbent has an average pore diameter of 3Å to 5Å inclusive.

[0007] Item 2. The method for removing H₂S according to Item 1, wherein the adsorption step is performed at -10°C to 40°C inclusive.

[0008] Item 3. In the adsorption step, a contact time W / F of the gas composition with respect to the adsorbent is 0.1 g·sec / cc to 50 g·sec / cc inclusive, wherein W represents the mass (g) of the adsorbent, and F represents the flow rate (cc / sec) of the gas composition, the method for removing H₂S according to Item 1 or 2 above.

[0009] Item 4. The method for removing H₂S according to any one of Items 1 to 3 above, wherein in the adsorption step, the removal rate of H₂S from the gas composition is 5% or more.

[0010] Item 5. The gas composition further contains H₂O, wherein in the adsorption step, H₂O is adsorbed onto the adsorbent, the method for removing H₂S according to any one of Items 1 to 4 above.

[0011] Item 6. The gas composition further contains CS₂, wherein in the adsorption step, CS₂ is adsorbed onto the adsorbent, the method for removing H₂S according to any one of Items 1 to 5 above.

[0012] Item 7. The method for removing H₂S according to Item 6 above, wherein in the adsorption step, the decomposition rate of CS₂ is 5% or less.

[0013] Item 8. The method for removing H₂S according to any one of Items 1 to 7 above, wherein the adsorbent comprises zeolite.

[0014] Item 9. The method for removing H₂S according to any one of Items 1 to 8 above, further comprising a pretreatment step of performing heat treatment at 50°C to 400°C inclusive on the adsorbent before the adsorption step.

[0015] Item 10. An etching gas comprising 99% by volume or more of COS, and 0.0001% by volume or more and 0.40% by volume or less of H2S.

[0016] Item 11. The etching gas according to Item 10 above, wherein the H2O content of the etching gas is 10 ppm by volume or less.

[0017] Item 12. The etching gas according to Item 10 or 11 above, wherein the CS2 content of the etching gas is 0.1% by volume or less.

[0018] Item 13. A method for producing the etching gas according to any one of Items 10 to 12 above, comprising: a step of preparing a gas composition containing COS and H2S; and an adsorption step of bringing the gas composition into contact with an adsorbent to cause the adsorbent to adsorb H2S, wherein the average pore diameter of the adsorbent is 3 Å or more and 5 Å or less.

Effects of the Invention

[0019] According to the present disclosure, it is possible to provide a method for removing H2S from a gas composition containing COS and H2S without reducing the amount of COS.

[0020] Furthermore, according to the present disclosure, it is possible to provide an etching gas containing COS and H2S suitable for anisotropic processing, and a method for producing the etching gas.

Brief Description of Drawings

[0021] [Figure 1] It is a table showing the results of Study 1. [Figure 2] It is a table showing the results of Study 2. [Figure 3] It is a table showing the results of Study 3. [Figure 4] It is a figure for explaining the side etch rate.

Mode for Carrying Out the Invention

[0022] In this disclosure, when a numerical range is indicated as "A to B", it means A or greater and B or less. If no unit is specified for A, but a unit is specified only for B, the units for A and B are the same.

[0023] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0024] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0025] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0026] Crude COS produced in factories contains impurities such as unreacted sulfur and carbon monoxide. To remove these impurities from the crude COS, it is necessary to pass the crude COS gas through H2O. However, when crude COS gas is passed through H2O, the COS in the crude COS gas reacts with the H2O, resulting in the excessive production of H2S.

[0027] Furthermore, when crude COS gas is brought into contact with an adsorbent to remove impurities, the amount of COS in the gas decreases after contact with the adsorbent. This is presumed to be because, upon contact between the crude COS gas and the adsorbent, the COS in the crude COS gas reacts with H2O contained as an impurity in the crude COS gas, and / or H2O attached to the adsorbent, causing the COS to decompose.

[0028] As a result of diligent research, the Disclosers have discovered that H2S can be removed from a gas composition containing COS and H2S without a reduction in COS by a method that includes an adsorption step of contacting the gas composition containing COS and H2S with an adsorbent having an average pore size of 3 Å to 5 Å, and have completed the method for removing H2S from a gas composition containing COS and H2S as disclosed herein.

[0029] Furthermore, as a result of diligent research, the Disclosers have found that an etching gas containing 99% or more by volume of COS and 0.0001% to 0.40% by volume of H2S is suitable for anisotropic processing, and have completed the etching gas and a method for producing the etching gas described herein.

[0030] [Embodiment 1: Method for removing H2S from a gas composition containing COS and H2S] A method for removing H2S from a gas composition containing COS and H2S according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") (hereinafter also referred to as "H2S removal method") is an H2S removal method that includes an adsorption step of contacting the gas composition containing COS and H2S with an adsorbent to adsorb H2S onto the adsorbent. The average pore size of the adsorbent is 3 Å or more and 5 Å or less.

[0031] <Gas composition> In Embodiment 1, the composition of the gas composition containing COS and H2S that is the target of the H2S gas removal method is not particularly limited as long as it contains COS and H2S. The COS content of the gas composition after passing a typical crude COS produced in a factory through water is, for example, 95% to 99.6% by volume, and the H2S content is 0.4% to 5% by volume. Furthermore, if rectification is performed after passing the crude COS through water, the COS content of the gas composition after rectification is, for example, 99.7% to 99.99% by volume, and the H2S content is 0.01% to 0.3% by volume. Based on the above, the gas composition that is the target of the H2S gas removal method in Embodiment 1 can contain 95% to 99.99% by volume of COS and 0.01% to 5% by volume of H2S.

[0032] The gas composition targeted by the H2S gas removal method may contain other components in addition to COS and H2S. Examples of other components include H2O, CS2, N2, O2, CH4, CO, and CO2. The content of other components in the gas composition is not particularly limited. For example, the gas composition may contain H2O in an amount of 1 volume ppm to 200 volume ppm. For example, the gas composition may contain CS2 in an amount of 0.01 volume% to 0.1 volume%. The gas composition may contain other components other than H2O and CS2 in total in an amount of 0.001 volume% to 1 volume%.

[0033] <Adsorption process> In the adsorption process, the gas composition is brought into contact with an adsorbent to adsorb H2S onto the adsorbent. The average pore size of the adsorbent is between 3 Å and 5 Å. When the average pore size of the adsorbent is between 3 Å and 5 Å, H2S can be removed from the gas composition containing COS and H2S without a decrease in COS. If the average pore size of the adsorbent is less than 3 Å, H2S is less likely to be adsorbed onto the adsorbent because the size of the H2S molecule is 2.2 Å. If the average pore size of the adsorbent is greater than 5 Å, COS and H2O react more easily within the pores, and the amount of COS in the gas composition after the adsorption process decreases.

[0034] From the viewpoint of improving the adsorption performance of H2S, the average pore size of the adsorbent is preferably 4 Å or more and 5 Å or less. From the viewpoint of suppressing the decomposition of COS, the average pore size of the adsorbent is preferably 3 Å or more and 4 Å or less.

[0035] In this disclosure, the pore diameter of the adsorbent refers to the diameter D assuming the pore shape is cylindrical with diameter D and height H. In this disclosure, the average pore diameter of the adsorbent refers to the arithmetic mean of the pore diameters of multiple pores in the adsorbent. In this disclosure, the average pore diameter of the adsorbent is determined by adsorption isotherm measurement using a BELSORP MINI manufactured by MICROTRAC. Nitrogen gas is used as the measurement gas.

[0036] In this disclosure, there are no particular restrictions on the form in which the adsorbent is used. A continuous gas flow system is used, in which the gas composition is passed through a device (such as a column) filled with the adsorbent. Alternatively, a batch system is used, in which the gas composition is filled into a container filled with the adsorbent, and the purified gas composition is recovered after a predetermined time has elapsed.

[0037] The adsorption process may be performed once or two or more times. The number of adsorption processes may be 2 to 10 times, 2 to 7 times, or 3 to 5 times. When the adsorption process is performed two or more times, the same adsorbent may be used in each adsorption process, or different adsorbents may be used. For example, when the adsorption process is performed twice, the same adsorbent may be used in the first and second processes, or the adsorbent used in the first process may be regenerated by heating it above the adsorption temperature to remove the adsorbed material, and this regenerated adsorbent may be used in the second process. Alternatively, the adsorbent used in the first and second processes may be different. Furthermore, when the adsorption process is performed three or more times, various configurations are possible, such as using the same adsorbent in the first and second processes and a different adsorbent in the third process, or using different adsorbents in all three processes.

[0038] The adsorption process is preferably carried out at a temperature between -10°C and 40°C. Carrying the adsorption process at a temperature above -10°C is preferable from the viewpoint of improving adsorption efficiency. Carrying the adsorption process at a temperature below 40°C is preferable from the viewpoint of suppressing side reactions (isomerization reactions) during contact between the gas composition and the adsorbent. The temperature at which the adsorption process is carried out is more preferably between 0°C and 30°C, and even more preferably between 10°C and 25°C.

[0039] In the adsorption process, the contact time W / F of the gas composition with the adsorbent is preferably 0.1 g·sec / cc or more and 50 g·sec / cc or less. Here, W represents the mass (g) of the adsorbent and F represents the flow rate (cc / sec) of the gas composition. The larger the W / F, the longer the contact time between the gas composition and the catalyst, and the higher the removal rate of H2S from the gas composition. Therefore, a W / F of 0.1 g·sec / cc or more is preferable from the viewpoint of improving the removal rate of H2S. A W / F of 50 g·sec / cc or less is preferable from the viewpoint of improving the efficiency of removing H2S from a gas composition containing COS and H2S. A W / F of 1 g·sec / cc or more and 30 g·sec / cc or less is more preferable, and a W / F of 4 g·sec / cc or more and 20 g·sec / cc or less is even more preferable.

[0040] The contact times described above are for reactions carried out in the gas phase, particularly in a continuous gas flow system, but they can also be adjusted as appropriate when the reaction is carried out in a batch system.

[0041] In the adsorption process, the removal rate of H2S from the gas composition is preferably 5% or more, more preferably 20% or more, even more preferably 30% or more, or even more preferably 40% or more. The removal rate of H2S from the gas composition can be 100% or less. The H2S removal rate is calculated by measuring the H2S content of the gas composition before the adsorption process and the H2S content of the gas composition after the adsorption process, and using the following formula. H2S removal rate (%) = {(H2S content before adsorption process - H2S content after adsorption process) / (H2S content before adsorption process)} × 100

[0042] The above H2S content is measured using gas chromatography-mass spectrometry (electron ionization method (EI method)) under the following conditions. Measurement conditions: Column / GS-GasPro Calculation of content: Calculated from the TIC (Total Ion Current) chromatogram peak area ratio. The CS2 content and COS content of the gas compositions described later are also measured under the same conditions using gas chromatography-mass spectrometry.

[0043] If the adsorption process is performed two or more times, the H2S content after the adsorption process is the H2S content of the gas composition after the last adsorption process.

[0044] If the gas composition contains H2O in addition to COS and H2S, H2O can be adsorbed onto the adsorbent in the adsorption step. In the adsorption step, the removal rate of H2O from the gas composition is preferably 94% or higher, more preferably 95% or higher, even more preferably 97% or higher, even more preferably 98% or higher, or most preferably 99% or higher. The removal rate of H2O from the gas composition can be 100% or less. The removal rate of H2O is calculated by measuring the H2O content of the gas composition before the adsorption step and the H2O content of the gas composition after the adsorption step, and using the following formula. H2O removal rate (%) = {(H2O content before adsorption process - H2O content after adsorption process) / (H2O content before adsorption process)} × 100

[0045] The above H2O content is measured using a quartz crystal oscillating moisture meter.

[0046] If the gas composition contains CS2 in addition to COS and H2S, CS2 can be adsorbed onto the adsorbent during the adsorption process. On the other hand, if the average pore size of the adsorbent is greater than 5 Å, COS and H2S are likely to react within the pores to generate CS2. If the amount of CS2 generated is greater than the amount of CS2 adsorbed, the amount of CS2 in the gas composition after the adsorption process will increase. In the adsorption process of Embodiment 1, the average pore size of the adsorbent is between 3 Å and 5 Å, so the reaction between COS and H2S within the pores is unlikely to occur, and CS2 is unlikely to be generated. Therefore, in the adsorption process of Embodiment 1, it is easy to reduce the amount of CS2 in the gas composition.

[0047] In the adsorption step, the decomposition rate of CS₂ in the gas composition is preferably -15% or more and 5% or less, more preferably -12% or more and 4% or less, still more preferably -10% or more and 3% or less, even more preferably -8% or more and 1.5% or less, and most preferably -5% or more and 0% or less. The above decomposition rate is calculated by the following formula after measuring the CS₂ content of the gas composition before the adsorption step and the CS₂ content after the adsorption step. CS₂ decomposition rate (%) = {(CS₂ content after adsorption step - CS₂ content before adsorption step) / (CS₂ content before adsorption step)} × 100 When the CS₂ decomposition rate is positive, it indicates that the amount of CS₂ produced is larger than the amount of CS₂ adsorbed. When the CS₂ decomposition rate is zero or less, it indicates that the amount of CS₂ adsorbed is larger than the amount of CS₂ produced. In the present disclosure, a CS₂ decomposition rate of 5% or less indicates that the amount of CS₂ produced is sufficiently suppressed.

[0048] The adsorbent preferably contains at least one selected from the group consisting of, for example, zeolite, activated carbon, alumina, and silica-alumina. Among these, the adsorbent preferably contains zeolite, or more preferably consists of zeolite.

[0049] Zeolite is a type of clay mineral, and is a hydrated aluminosilicate containing an alkali or alkaline earth metal that consists of a rigid anionic framework having regular channels (tubular pores) and cavities (voids).

[0050] Zeolite is generally represented as (M I ,M II 1 / 2 ) m (Al m Si n O 2(m+n) )· x H₂O, (n≧m) (M I :Li + , Na + , K + , etc., M II :Ca 2+ , Mg 2+ , Ba2+ etc.) It is represented by the following composition, where the cations compensate for the negative charge of the aluminosilicate skeleton.

[0051] Furthermore, there are no particular restrictions on the types of cations in the zeolite; typically, H + Li + na + , K + Ca 2+ Mg 2+ Ba 2+ These are used.

[0052] The basic structural unit of zeolites is a tetrahedral structure of SiO4 or AlO4 (collectively called a TO4 tetrahedron), which is infinitely linked in three dimensions to form a crystal. Zeolite crystals are porous, with pore diameters typically around 0.2 to 1.0 nm. Zeolites exhibit molecular sieving properties, meaning that molecules larger than their pore diameter cannot enter the pores. In addition to the molecular sieving effect due to the pores derived from their skeletal structure, zeolites possess properties such as solid acidity, ion exchange capacity, catalytic activity, and adsorption capacity.

[0053] Zeolites with an average pore size of 3 Å to 5 Å are commercially available. Examples include Molecular Sieves 3A (average pore size of 3 Å) (manufactured by Tosoh Corporation), Molecular Sieves 4A (average pore size of 4 Å) (manufactured by Tosoh Corporation), Molecular Sieves 5A (average pore size of 5 Å) (manufactured by Tosoh Corporation), and AR300 (average pore size of 4 Å) (manufactured by Resonaq Universal Corporation). These zeolites can be used individually or in combination of two or more types, as long as the average pore size requirement is met.

[0054] In this disclosure, the adsorbent may be subjected to a heat treatment at a temperature of 50°C to 400°C before the adsorption process. This causes H2O attached to the adsorbent to detach from the zeolite, improving the adsorption performance of the adsorbent. The heat treatment may be performed, for example, in a vacuum (1 to 90 kPa abs.) for 1 to 48 hours. Adsorbents that have not undergone heat treatment can also be suitably used in this disclosure.

[0055] In this disclosure, the adsorbent may be used in powder, granular, or pellet form. The adsorbent may also be used as a molded body. Industrially, it is preferable to use it as a molded body. There are no particular restrictions on the shape of the molded body, but it is preferable to use it in a cylindrical shape with a diameter of about 0.5 to 5 mm and a length of about 1 to 15 mm, or a spherical shape with a diameter of about 0.5 to 10 mm.

[0056] This disclosure does not particularly limit the method for manufacturing the molded body of the adsorbent, and conventionally known methods using kaolin clay as a binder can be employed, for example.

[0057] The composition of the gas composition after the adsorption process is not particularly limited, as long as the COS is not reduced and the H2S is reduced compared to the gas composition before the adsorption process. The description of the composition of the gas composition after the adsorption process is the same as the description of the etching gas composition in Embodiment 2.

[0058] [Embodiment 2: Etching Gas] The etching gas according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is an etching gas containing 99% or more by volume of COS and 0.0001% to 0.40% by volume of H2S.

[0059] The etching gas of Embodiment 2 contains 99% or more by volume of COS and is therefore suitable for etching amorphous carbon masks. From the viewpoint of improving etching efficiency, the COS content of the etching gas is preferably 99.0% or more by volume, more preferably 99.5% or more by volume, even more preferably 99.9% or more by volume, or even more preferably 99.99% or more by volume. The upper limit of the COS content of the etching gas is not particularly limited as long as it can contain 0.0001% or more by volume of H2S. The COS content of the etching gas is preferably 99% or more by volume and 99.999% or less by volume, more preferably 99.5% or more by volume and 99.995% or less by volume, even more preferably 99.9% or more by volume and 99.99% or less by volume, or even more preferably 99.92% or more by volume and 99.95% or less by volume.

[0060] The etching gas of Embodiment 2 contains H2S in an amount of 0.0001% to 0.40% by volume along with COS, making it suitable for anisotropic processing. From the viewpoint of improving the performance of anisotropic processing, the H2S content of the etching gas is preferably 0.0001% or more by volume, more preferably 0.001% or more by volume, even more preferably 0.01% or more by volume, or even more preferably 0.1% or more by volume. From the viewpoint of suppressing corrosion of containers and piping, the H2S content of the etching gas is preferably 0.4% or less by volume, more preferably 0.3% or less by volume, even more preferably 0.2% or less by volume, or even more preferably 0.15% or less by volume.

[0061] The etching gas of Embodiment 2 may contain H2O. From the viewpoint of suppressing the decomposition of COS, the H2O content of the etching gas is preferably 10 volume ppm or less, more preferably 5 volume ppm or less, even more preferably 3 volume ppm or less, or even more preferably 1 volume ppm or less. The H2O content of the etching gas is most preferably below the detection limit, but from a manufacturing viewpoint, it can be 0.1 volume ppm or more.

[0062] The etching gas of Embodiment 2 may contain CS2. From the viewpoint of improving the performance of anisotropic processing, the CS2 content of the etching gas is preferably 0.1 volume% or less, more preferably 0.05 volume% or less, or even more preferably 0.01 volume% or less. The CS2 content of the etching gas is most preferably below the detection limit, but from a manufacturing viewpoint, it can be 0.005 volume% or more.

[0063] In this disclosure, the COS content, H2S content, H2O content, and CS2 content of the etching gas can be a combination of the above ranges.

[0064] In this disclosure, the COS content, H2S content, H2O content, and CS2 content of the etching gas are measured using gas chromatography-mass spectrometry. The measurement conditions are the same as those described in Embodiment 1.

[0065] The etching gas of Embodiment 2 can be used in the same etching method as conventional methods, preferably a dry etching method. The etching conditions can be, for example, the following conditions. Flow rate: 5-2000 sccm, preferably 10-1000 sccm; • Discharge power: 200-20000W, preferably 400-10000W; • Bias power: 25-15000W, preferably 100-10000W; • Pressure (gauge pressure): 30 mTorr or less (3.99 Pa or less), preferably 2 to 10 mTorr (0.266 to 1.33 Pa); ·Electron density: 10 9 ~10 13 cm -3 Preferably 10 10 ~10 12 cm -3 ; • Electronic temperature: 2-9 eV, preferably 3-8 eV; • Wafer temperature: -40 to 100°C, preferably -30 to 50°C; Chamber wall temperature: -30 to 300°C, preferably 20 to 200°C.

[0066] [Embodiment 3: Method for producing etching gas] The etching gas production method of one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 3") is the etching gas production method described in Embodiment 2. The etching gas production method of Embodiment 3 includes a step of preparing a gas composition containing COS and H2S (hereinafter also referred to as the "preparation step") and an adsorption step of contacting the gas composition with an adsorbent to adsorb H2S onto the adsorbent. The average pore size of the adsorbent is 3 Å or more and 5 Å or less.

[0067] The composition of the gas composition containing COS and H2S prepared in the preparation step of Embodiment 3 (COS content, H2S content, H2O content, and CS2 content) is the same as that of the gas composition described in Embodiment 1. For example, the gas composition prepared in Embodiment 2 preferably contains 95% to 99.99% by volume of COS and 0.01% to 5% by volume of H2S, and more preferably contains 99% to 99.999% by volume of COS and 0.0001% to 0.4% by volume of H2S.

[0068] The description of the adsorption process in Embodiment 3 is the same as the description of the adsorption process in Embodiment 1. [Examples]

[0069] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0070] The COS, H2S, and CS2 content of the gas composition before and after the adsorption process were measured using the following measuring device and conditions. The H2O content was measured using the following moisture meter.

[0071] Measurement device: Gas chromatography-mass spectrometer (using electron ionization method (EI method)) Measurement conditions: Column / GS-GasPro Calculation of content: Calculated from the TIC (Total Ion Current) chromatogram peak area ratio. Measurement of H2O content: Measured using a quartz oscillator type moisture meter.

[0072] The following adsorbents were prepared as adsorbents. MS3A: Manufactured by Tosoh Corporation, Molecular Sieves 3A (average pore diameter 3 Å), SiO2 / Al2O3 ratio = 2.3, cation K, crystal structure type A) MS4A: Manufactured by Tosoh Corporation, Molecular Sieves 34A (average pore diameter 4 Å), SiO2 / Al2O3 ratio = 2.3, cation Na, crystal structure type A) MS5A: Manufactured by Tosoh Corporation, Molecular sieves 5A (average pore diameter 5 Å), SiO2 / Al2O3 ratio = 2.3, cation Ca, crystal structure type A) AR300: Manufactured by Resonaq Universal, (average pore diameter 4 Å), SiO2 / Al2O3 ratio = 9.2, cation Ca, crystal structure mordenite) AW500: Manufactured by Resonaq Universal, (average pore diameter 6 Å), SiO2 / Al2O3 ratio = 5, cation Ca, crystal structure chabacite) Zeolite 920: Manufactured by Tosoh Corporation, (average pore size 6.5 Å), SiO2 / Al2O3 ratio = 40, cation H, crystal structure beta)

[0073] [Study 1: Examination of gas compositions with high H2S content] In Study 1, the adsorption process was carried out by contacting the gas composition shown in "Gas Composition Before Adsorption Process" in Table 1 of Figure 1 with the adsorbent shown in "Type" of "Adsorbent" in Table 1. The temperature of the adsorption process for each sample is as shown in the "Temperature" column of Table 1. The adsorbent was used in either a continuous gas flow system (indicated as "Flow" in Table 1) or a batch system (indicated as "Batch" in Table 1).

[0074] The specific method for the continuous gas-phase flow system is as follows: A predetermined amount of adsorbent was packed into a 3 / 4-inch, 20 cm long stainless steel (SUS) tube, and the temperature was set to the temperature shown in Table 1. After the set temperature was reached, the flow rate of COS was determined so that the W / F ratio was a predetermined value, and the COS was allowed to flow through the SUS tube. After a certain period of time, the outlet gas was sampled, and the composition of the outlet gas was analyzed using a gas chromatography-mass spectrometer and QMA. The W / F ratio for each sample is shown in the "W / F" column of Table 1.

[0075] The specific batch method is as follows: 3g of adsorbent was packed into a 100cc metal container, followed by 30g of COS. The container was heated to the temperature shown in Table 1 and maintained at that temperature for 100 hours. After 100 hours, the gas was sampled, and the composition of the outlet gas was analyzed using a gas chromatography-mass spectrometer and QMA.

[0076] For samples where "Yes" is indicated under "Heat Treatment" in Table 1, the adsorbent was subjected to a heat treatment at 200°C for 3 hours in a vacuum (1 kPa abs.) before contacting the gas composition with the adsorbent.

[0077] The COS, H2S, CS2, and H2O content of the gas composition after the adsorption process were measured. The results are shown in Table 1.

[0078] Samples 1 to 13 correspond to the examples. These samples demonstrated that H2S could be removed without a decrease in COS in the gas composition by contacting the gas composition with an adsorbent.

[0079] Samples 101 to 103 are comparative examples. In these samples, contact with the adsorbent reduced the amount of COS in the gas composition. Furthermore, in sample 102, the amount of H2S in the gas composition increased.

[0080] [Study 2: Examination of gas compositions with low H2S content] In Study 2, the adsorption process was carried out by contacting a gas composition with the composition shown in "Gas Composition Before Adsorption Process" in Table 2 of Figure 2 with the adsorbent shown in "Type" of "Adsorbent" in Table 2. The description of the adsorption process in Study 2 is the same as the description of the adsorption process in Study 1.

[0081] The COS, H2S, CS2, and H2O content of the gas composition after the adsorption process were measured. The results are shown in Table 2 of Figure 2.

[0082] Samples 21 to 32 correspond to the examples. These samples demonstrated that H2S could be removed without a decrease in COS in the gas composition by contacting the gas composition with an adsorbent.

[0083] Samples 201 and 202 are comparative examples. In these samples, the COS in the gas composition decreased when the gas composition was brought into contact with the adsorbent.

[0084] [Consideration 3: Examination of etching gas] An amorphous carbon film on a silicon wafer was etched using an etching gas with the composition shown in Table 3 of Figure 3. Specifically, the etching gas was introduced through a gas inlet connected to the upper electrode, and then the etching gas was excited by a high-frequency power supply (13.56 MHz, 0.22 W) to perform etching. The etching conditions were as follows:

[0085] <Etching conditions> ·Flow rate: 10sccm; ·Discharge power: 1000W; • Bias power: 300W; • Pressure (gauge pressure): 3.2 mTorr; ·Electron density: 10 11 cm -3 ; ·Electron temperature: 4eV; • Wafer temperature: 25°C; Chamber wall temperature: 100℃.

[0086] After etching, the edge face of the silicon wafer was observed using a scanning electron microscope (SEM) to determine the side etching rate. The relative ratio of the side etching rate to that of a comparative example is shown in the table below. The side etching rate R is the ratio of the amount of side etching a to the diameter b of the pores 2 formed in the amorphous carbon film 1 shown in Figure 1, and is calculated using the following formula. A smaller side etching rate indicates that the etching gas is more suitable for anisotropic processing. R=a / b

[0087] The etching gas used in the example was found to have a lower side etching rate compared to the etching gas used in the reference example, making it suitable for anisotropic machining.

[0088] In the comparative example, the etching gas caused pore clogging, and etching was not possible. [Explanation of symbols]

[0089] 1. Amorphous carbon film 2 holes

Claims

1. COS and H ２ From a gas composition containing S, H ２ A method for removing S, The gas composition is brought into contact with the adsorbent, and H is added to the adsorbent. ２ Includes an adsorption step to adsorb S, The average pore size of the adsorbent is 3 Å or more and 5 Å or less. ２ A method to remove S.

2. The adsorption step is performed at a temperature of -10°C or higher and 40°C or lower, as described in claim 1. ２ A method to remove S.

3. In the adsorption step, the contact time W / F of the gas composition with the adsorbent is 0.1 g / sec / cc or more and 50 g / sec / cc or less. H according to claim 1 or claim 2, wherein W represents the mass (g) of the adsorbent and F represents the flow rate (cc / sec) of the gas composition. ２ A method to remove S.

4. In the adsorption step, H from the gas composition ２ The removal rate of S is 5% or more, according to claim 1 or claim 2 of H ２ A method to remove S.

5. Said gas composition further comprises H ２ O In the adsorption step, H is added to the adsorbent. ２ H according to claim 1 or claim 2, which adsorbs O. ２ A method to remove S.

6. The gas composition further contains CS ２ Includes, In the adsorption step, the adsorbent is given CS ２ H according to claim 1 or claim 2, which adsorbs ２ A method to remove S.

7. In the adsorption step, CS ２ The H according to claim 6, the decomposition rate is 5% or less. ２ A method to remove S.

8. The adsorbent comprises zeolite, as described in claim 1 or claim 2. ２ A method to remove S.

9. The H according to claim 1 or claim 2, which includes a pretreatment step of heating the adsorbent to a temperature of 50°C or higher and 400°C or lower before the adsorption step. ２ A method to remove S.

10. COS at 99% by volume or more, and H ２ Etching gas containing 0.0001% to 0.40% by volume of sulfur.

11. The etching gas H ２ The etching gas according to claim 10, wherein the oxygen content is 10 ppm by volume or less.

12. The etching gas CS ２ The etching gas according to claim 10 or claim 11, wherein the content is 0.1 volume percent or less.

13. A method for producing an etching gas according to claim 10 or claim 11, COS and H ２ A step of preparing a gas composition containing S, The gas composition is brought into contact with the adsorbent, and H is added to the adsorbent. ２ Includes an adsorption step to adsorb S, A method for producing etching gas, wherein the average pore size of the adsorbent is 3 Å or more and 5 Å or less.

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