Etching gas and method for producing the same, etching method, and method for producing semiconductor device

Abstract

Provided are an etching gas and etching method making it possible to selectively etch an etching target that contains silicon, more than etching with respect to a non-etching target. The etching gas contains a fluorobutene represented by general formula C4ＨxFy, where x is 1 to 7, y is 1 to 7, and x+y is 8. The etching gas also contains carbonyl fluoride as an impurity, the concentration of carbonyl fluoride being 100 mass ppm or less. The etching method comprises an etching step for: bringing an etching gas into contact with a member to be etched (12) that includes an etching target which is to be etched with the etching gas and a non-etching target which is not to be etched with the etching gas; and etching the etching target more selectively than the non-etching target. The etching target contains silicon.

Description

[Technical Field]

[0001] The present invention relates to an etching gas and a method for producing the same, an etching method, and a method for producing a semiconductor device. [Background technology]

[0002] In semiconductor manufacturing processes, dry etching is used to pattern and remove silicon compounds such as silicon oxide and silicon nitride. Dry etching requires high etching selectivity, i.e., the ability to selectively etch silicon compounds compared to the resists and masks used for patterning.

[0003] Various etching gases that satisfy this requirement have been proposed, and for example, Patent Document 1 discloses an etching gas made of hexafluorobutene. Also, Patent Document 2 discloses an etching gas containing hexafluorobutene and hexafluorobutyne. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 6257638 [Patent Document 2] Japanese Patent Publication No. 6462699 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when etching is performed using the etching gases disclosed in Patent Documents 1 and 2, etching selectivity may be insufficient. An object of the present invention is to provide an etching gas that can selectively etch an etching target compared to a non-etching target when an etching gas is brought into contact with an etching target member having an etching target that is to be etched by the etching gas and a non-etching target that is not to be etched by the etching gas, a method for producing the same, an etching method, and a method for producing a semiconductor element. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is as follows [1] to

[11] . [1] General formula C4H x F y In the general formula, x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8, An etching gas containing carbonyl fluoride as an impurity, the concentration of carbonyl fluoride being 100 mass ppm or less.

[0007] [2] The etching gas according to [1], further containing hydrogen fluoride as an impurity, wherein the concentration of hydrogen fluoride is 100 ppm by mass or less. [3] A method for producing the etching gas according to [1] or [2], a dehydration step of subjecting the crude fluorobutene containing water and oxygen gas to a dehydration treatment; a deoxidizing step of subjecting the crude fluorobutene to a deoxidizing gas treatment; An etching gas manufacturing method comprising:

[0008] [4] The method for producing an etching gas according to [3], wherein the dehydration step is followed by the deoxidation step. [5] The method for producing an etching gas according to [3] or [4], wherein the dehydration treatment is a treatment in which the crude fluorobutene is brought into contact with an adsorbent to adsorb water onto the adsorbent.

[0009] [6] The method for producing an etching gas according to any one of [3] to [5], further comprising a filling step of filling a filling container with the fluorobutene that has been subjected to the dehydration step and the deoxidation step.

[0010] [7] An etching method comprising an etching step of contacting the etching gas according to [1] or [2] with a member to be etched, the member having an etching object that is to be etched by the etching gas and a non-etching object that is not to be etched by the etching gas, and selectively etching the etching object compared to the non-etching object, wherein the etching object contains silicon.

[0011] [8] The etching method according to [7], wherein the etching gas is filled in a filling container, the gas phase in the filling container has a carbonyl fluoride concentration of 100 mass ppm or less, and in the etching step, the gas phase is extracted from the filling container and brought into contact with the member to be etched to etch the member to be etched.

[0012] [9] The etching method according to [7] or [8], wherein the etching gas is a gas consisting of only the fluorobutene, or a mixed gas containing the fluorobutene and a diluent gas.

[10] The etching method according to [9], wherein the dilution gas is at least one selected from nitrogen gas, helium, argon, neon, krypton, and xenon.

[0013]

[11] A method for manufacturing a semiconductor element using the etching method according to any one of [7] to

[10] , the member to be etched is a semiconductor substrate having the etching object and the non-etching object, A method for manufacturing a semiconductor device, comprising a processing step of removing at least a part of the etching object from the semiconductor substrate by etching. [Effects of the Invention]

[0014] According to the present invention, an etching target containing silicon can be selectively etched compared to a non-etching target. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of an example of an etching apparatus for explaining an embodiment of an etching method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described below. Note that this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0017] The etching gas according to this embodiment is a gas represented by the general formula CH x F y wherein x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8, and the etching gas contains carbonyl fluoride (COF2) as an impurity, and the concentration of carbonyl fluoride is 100 mass ppm or less.

[0018] The etching method according to the present embodiment includes an etching step of contacting the etching gas according to the present embodiment with a member to be etched, the member having an etching target to be etched by the etching gas and a non-etching target not to be etched by the etching gas, to selectively etch the etching target compared to the non-etching target. In the etching method according to the present embodiment, the etching target contains silicon (Si).

[0019] When the etching gas is brought into contact with a material to be etched, the silicon-containing material to be etched reacts with the fluorobutene in the etching gas, resulting in etching of the material. In contrast, the material to be etched, such as a mask, hardly reacts with the fluorobutene, so etching of the material to be etched hardly progresses. Therefore, according to the etching method of this embodiment, the material to be etched can be selectively etched relative to the material to be etched (i.e., high etching selectivity can be achieved).

[0020] Furthermore, the fluorobutene reacts and polymerizes during dry etching, and the non-etching target is covered with a polymer film to protect it from etching. Therefore, etching of the non-etching target becomes more difficult, and therefore etching selectivity is further improved by using an etching gas containing the fluorobutene.

[0021] However, carbonyl fluoride is highly reactive with both etching targets, such as silicon oxide and silicon nitride, and non-etching targets, such as masks. Therefore, when etching a member to be etched using an etching gas containing carbonyl fluoride, both the etching target and non-etching targets may be etched, resulting in insufficient etching selectivity. Therefore, in order to increase etching selectivity, it is necessary to reduce the concentration of carbonyl fluoride in the etching gas.

[0022] That is, the concentration of carbonyl fluoride in the etching gas must be 100 mass ppm or less, preferably 50 mass ppm or less, and more preferably 10 mass ppm or less. If etching is performed using an etching gas with a carbonyl fluoride concentration within the above range, the non-etching target is less likely to be etched, and therefore the etching selectivity of the etching target relative to the non-etching target is increased. The method for measuring the carbonyl fluoride concentration is not particularly limited, but it can be quantified, for example, by infrared spectroscopy.

[0023] Furthermore, hydrogen fluoride (HF) also has the same effect as carbonyl fluoride and is highly reactive with both etching targets such as silicon oxide and silicon nitride and non-etching targets such as masks, so the concentration of hydrogen fluoride in the etching gas is preferably low. That is, when the etching gas further contains hydrogen fluoride as an impurity, the concentration of hydrogen fluoride in the etching gas is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and even more preferably 10 mass ppm or less. The method for measuring the concentration of hydrogen fluoride is not particularly limited, but it can be quantified, for example, by infrared spectroscopy.

[0024] As described above, the etching gas according to this embodiment has a low concentration of carbonyl fluoride, and therefore, when dry etching of a member to be etched is performed using the etching gas according to this embodiment, the non-etching object is less likely to be etched, and the etching object can be selectively etched compared to the non-etching object, resulting in high etching selectivity.

[0025] For example, the etching selectivity, which is the ratio of the etching rate of an object to be etched to the etching rate of an object not to be etched, is likely to be 10 or more. The etching selectivity is preferably 10 or more, more preferably 30 or more, and even more preferably 50 or more.

[0026] Carbonyl fluoride and hydrogen fluoride are impurities derived from the fluorobutene. The reason why the fluorobutene is likely to contain carbonyl fluoride and hydrogen fluoride as impurities will be explained below.

[0027] The above-mentioned fluorobutene often contains small amounts of oxygen gas (O2) and water (HO), but if the oxygen concentration in the fluorobutene exceeds 1000 mass ppm, the fluorobutene and oxygen gas react to produce carbonyl fluoride and hydrogen fluoride as shown in the following formula. The presence of water in the fluorobutene promotes the reaction shown in the following formula. C4H x F y +(4-(yx) / 4)O2→ (yx) / 2COF2+xHF+(4-(yx) / 2)CO2

[0028] As described above, the reaction between the fluorobutene and oxygen gas produces carbonyl fluoride and hydrogen fluoride. Therefore, when producing the etching gas according to this embodiment containing the fluorobutene, it is necessary to remove water and oxygen gas from the fluorobutene in order to reduce the concentrations of carbonyl fluoride and hydrogen fluoride.

[0029] That is, the method for producing an etching gas according to this embodiment comprises a dehydration step in which crude fluorobutene, which is the fluorobutene containing water and oxygen gas, is dehydrated, and a deoxygenation step in which the crude fluorobutene is deoxygenated. The order in which the dehydration step and the deoxygenation step are performed is not particularly limited, and either step can be performed first. Furthermore, if possible, the dehydration step and the deoxygenation step may be performed simultaneously.

[0030] In the present invention, etching means removing part or all of the etching target material of the etched member to process the etched member into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing a film-like etching target material made of a silicon compound that is present in the etched member to a predetermined film thickness).

[0031] The etching method according to the present embodiment can be used in the manufacture of semiconductor devices. That is, the method for manufacturing a semiconductor device according to the present embodiment is a method for manufacturing a semiconductor device using the etching method according to the present embodiment, in which the member to be etched is a semiconductor substrate having an etching target and a non-etching target, and the method includes a process of removing at least a part of the etching target from the semiconductor substrate by etching.

[0032] The etching method according to this embodiment can etch an etching target with high precision, and therefore can be used for manufacturing semiconductor devices such as 3D-NAND flash memories, logic devices, etc. Furthermore, the etching method according to this embodiment is expected to contribute to further miniaturization and higher integration of semiconductor devices.

[0033] The etching gas, the method for producing the etching gas, the etching method, and the method for producing a semiconductor device according to this embodiment will be described in further detail below. [Fluorobutene] The fluorobutene contained in the etching gas according to this embodiment is represented by the general formula CH x F y and satisfies three conditions: x in the general formula is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8. The type of fluorobutene is not particularly limited as long as it satisfies the above requirements, and both linear fluorobutene and branched fluorobutene (isobutene) can be used, but those similar to fluoro-1-butene and fluoro-2-butene are preferably used.

[0034] Specific examples of fluoro-1-butene include CHF2-CF2-CF=CF2, CF3-CF2-CF=CHF, CF3-CHF-CF=CF2, CF3-CF2-CH=CF2, CHF2-CHF-CF=CF2, CHF2-CF2-CF=CHF, CF3-CHF-CF=CHF, CF3-CF2-CH=CHF, CF3-CHF-CH=CF2, CHF2-CF2-CH=CF2, CH3-CF2-CF=CF2, CH2F-CHF-CF=CF2, CH2F-CF2-CH=CF2, CH2F-CF2-CF=CHF, CHF2-CH2-CF=CF2, CHF2-CHF-CH=CF2, CHF2-CHF-CF=CHF, CHF2-CF2-CH=CHF, CHF2-CF2-CF=CH2, CF3-CH2-CH=CF2, CF3-CH2-CF=CHF, CF3-CHF-CH=CHF, CF3-CHF-CF=CH2, CF3-CF2-CH=CH2, CH3-CHF-CF=CF2, CH3-CF2-CH=CF2, CH3-CF2-CF=CHF, CH2F-CH2-CF=CF2, CH2F-CHF-CH=CF2, CH2F-CHF-CF=CHF, CH2F-CF2-CH=CHF, CH2F-CF2-CF=CH2, CHF2-CH2-CH=CF2, CHF2-CH2-CF=CHF, CHF2-CHF-CH=CHF, CHF2-CHF-CF=CH2, CHF2-CF2-CH=CH2, CF3-CHExamples include CH3-CH2-CH=CHF, CH3-CH2-CF=CH2, CH3-CHF-CH=CH2, and CH2F-CH2-CH=CH2.

[0035] Specific examples of fluoro-2-butene include CHF2-CF=CF-CF3, CF3-CH=CF-CF3, CH2F-CF=CF-CF3, CHF2-CH=CF-CF3, CHF2-CF=CF-CHF2, CF3-CH=CH-CF3, CH3-CF=CF-CF3, CH2F-CH= CF-CF3, CH2F-CF=CH-CF3, CH2F-CF=CF-CHF2, CHF2-CH=CH-CF3, CHF2-CF=CH-CHF2, CH3-CH=CF-CF3, CH3-CF=CH-CF3, CH3-CF=CF-CHF2, CH2F-CH=CH-CF3, CH2F -CH=CF-CHF2, CH2F-CF=CH-CHF2, CH2F-CF=CF-CH2F, CHF2-CH=CH-CHF2, CH3-CH=CH-CF3, CH3-CH=CF-CHF2, CH3-CF=CH-CHF2, CH3-CF=CF-CH2F, CH2F-CF=CH- CH2F, CH2F-CH=CH-CHF2, CH3-CH=CH-CHF2, CH3-CH=CF-CH2F, CH3-CF=CH-CH2F, CH3-CF=CF-CH3, CH2F-CH=CH-CH2F, CH3-CH=CH-CH2F, CH3-CH=CF-CH3.

[0036] These fluorobutenes may be used alone or in combination of two or more. Some of the fluorobutenes exist as cis-trans isomers, but both cis- and trans-fluorobutenes can be used in the etching gas according to this embodiment.

[0037] Among the above fluorobutenes, those having a boiling point of 50°C or less at 1 atmosphere are preferred, and those having a boiling point of 40°C or less are more preferred. If the boiling point is within the above range, the fluorobutene gas is less likely to liquefy inside the piping through which the fluorobutene gas is introduced when the fluorobutene gas is introduced into, for example, a plasma etching apparatus. This makes it possible to suppress the occurrence of problems caused by the liquefaction of the fluorobutene gas, thereby enabling the plasma etching process to be carried out efficiently.

[0038] [Etching gas] The etching gas is a gas containing the above-mentioned fluorobutene. The etching gas may be a gas consisting of only the above-mentioned fluorobutene, or may be a mixed gas containing the above-mentioned fluorobutene and a diluent gas. The diluent gas is preferably inert to the fluorobutene and the member to be etched. Alternatively, the etching gas may be a mixed gas containing the above-mentioned fluorobutene, a diluent gas, and an additive gas.

[0039] The dilution gas is preferably an inert gas, and specifically, at least one gas selected from nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used.

[0040] Examples of the additive gas that can be used include fluorocarbon gas and hydrofluorocarbon gas. Specific examples of fluorocarbons include carbon tetrafluoride (CF), hexafluoromethane (C2F6), and octafluoropropane (C3F8). Specific examples of hydrofluorocarbons include CF3H, CF2H2, CFH3, C2F4H2, C2F5H, C3F7H, C3F6H2, C3F5H3, C3F4H4, and C3F3H5. One of these additive gases may be used alone, or two or more may be used in combination.

[0041] The content of the dilution gas is preferably 90% by volume or less, more preferably 50% by volume or less, based on the total volume of the etching gas, and the content of the additive gas is preferably 50% by volume or less, more preferably 30% by volume or less, based on the total volume of the etching gas.

[0042] The content of the fluorobutene is preferably 5% by volume or more, more preferably 10% by volume or more, based on the total volume of the etching gas in order to improve the etching rate, and is preferably 90% by volume or less, more preferably 80% by volume or less, based on the total volume of the etching gas in order to reduce the amount of fluorobutene used.

[0043] [Method for producing etching gas] As described above, the method for producing an etching gas according to this embodiment includes a dehydration step in which crude fluorobutene, which is the fluorobutene containing water and oxygen gas, is subjected to a dehydration treatment, and an oxygen depletion step in which the crude fluorobutene is subjected to an oxygen depletion treatment.

[0044] The method for dehydration treatment to remove water from crude fluorobutene is not particularly limited, and known methods can be used. For example, a treatment in which crude fluorobutene is brought into contact with an adsorbent can be used. The dehydration treatment can be carried out by bringing crude fluorobutene into contact with the adsorbent and causing water to be adsorbed onto the adsorbent. In some cases, contacting crude fluorobutene with the adsorbent can remove at least one of carbonyl fluoride and hydrogen fluoride from the crude fluorobutene together with water.

[0045] The type of adsorbent is not particularly limited as long as it can remove water from the fluorobutene, and examples thereof include molecular sieve 3A, molecular sieve 4A, molecular sieve 5A, activated carbon, silica gel, etc. Among these exemplified adsorbents, molecular sieve 3A, which can selectively adsorb water, is more preferred.

[0046] The adsorbent for removing carbonyl fluoride can be any of the above-mentioned molecular sieves, and the adsorbent for removing hydrogen fluoride can be any of the above-mentioned molecular sieves or metal fluorides such as sodium fluoride.

[0047] When crude fluorobutene is contacted with the adsorbent, either gaseous or liquid fluorobutene may be contacted. The contact between crude fluorobutene and the adsorbent may be carried out in a flow system or a batch system. However, in order to minimize the water concentration in the fluorobutene, it is more preferable to employ a method in which liquid fluorobutene is contacted with the adsorbent in a batch system for 24 hours or more.

[0048] By the dehydration treatment, the water concentration in the fluorobutene is preferably reduced to 500 ppm by mass or less, more preferably 100 ppm by mass or less, and even more preferably 10 ppm by mass or less, which makes it difficult for carbonyl fluoride and hydrogen fluoride to be produced by the reaction of the above formula. The method for measuring the water concentration in the fluorobutene is not particularly limited, and for example, the water concentration can be determined by the Karl Fischer method.

[0049] The method of deoxygenation treatment for removing oxygen gas from crude fluorobutene is not particularly limited, and for example, a treatment in which crude fluorobutene is distilled to separate oxygen gas can be adopted. Note that by distilling crude fluorobutene, at least one of carbonyl fluoride and hydrogen fluoride can sometimes be removed from the crude fluorobutene together with oxygen gas.

[0050] The distillation method is not particularly limited as long as it can separate oxygen gas from crude fluorobutene, and for example, a batch distillation method or a continuous distillation method can be used. The type of distillation column used for distillation is not particularly limited, and for example, a plate column using sieve trays, bubble cap trays, etc., or a packed column filled with structured packing or random packing can be used. The distillation conditions are not particularly limited, but the number of theoretical plates is preferably 1 to 30, more preferably 3 to 10.

[0051] The temperature of the bottom (bottom) of the distillation column into which crude fluorobutene is charged during distillation is not particularly limited, but is preferably 10°C or higher and 80°C or lower, and more preferably 20°C or higher and 60°C or lower. The temperature at the top of the distillation column is not particularly limited, but is preferably -60°C or higher and 0°C or lower, and more preferably -50°C or higher and -20°C or lower.

[0052] By the deoxygenation gas treatment, the oxygen concentration in the fluorobutene is preferably reduced to 1000 mass ppm or less, more preferably 500 mass ppm or less, and even more preferably 100 mass ppm or less, which makes it difficult for carbonyl fluoride and hydrogen fluoride to be produced by the reaction of the above formula. The method for measuring the oxygen concentration in the fluorobutene is not particularly limited, and it can be determined quantitatively by gas chromatography, for example.

[0053] The method for producing an etching gas according to this embodiment may further include a filling step of filling a filling container with the fluorobutene, the content of which has been reduced by a dehydration step and an oxygen decomposition step.

[0054] When the etching gas is a mixed gas containing the above-mentioned fluorobutene and a diluent gas, the above-mentioned fluorobutene and the diluent gas may be mixed to form a mixed gas, and then the mixed gas may be filled into a filling container, or the above-mentioned fluorobutene and the diluent gas may be separately filled into filling containers, and then the mixed gas may be formed inside the filling container.

[0055] The method for filling the container with the fluorobutene is not particularly limited, and for example, a gas phase filling method or a liquid phase filling method can be used. When filling the container with the fluorobutene, oxygen gas in the container may be removed in advance by a heating vacuum method or the like. The material of the filling container is not particularly limited, but examples thereof include manganese steel, stainless steel, Hastelloy (registered trademark), and Inconel (registered trademark).

[0056] [Etching Method] The etching in this embodiment can be achieved by either plasma etching using plasma or plasmaless etching not using plasma, such as reactive ion etching (RIE), inductively coupled plasma (ICP) etching, capacitively coupled plasma (CCP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave plasma etching.

[0057] In plasma etching, the plasma may be generated in a chamber in which the member to be etched is placed, or the plasma generation chamber may be separated from the chamber in which the member to be etched is placed (i.e., remote plasma may be used). Etching using remote plasma may enable etching of silicon-containing etching targets with higher selectivity.

[0058] Furthermore, in the etching method according to the present embodiment, etching may be performed using an etching gas filled in a filling container. That is, the etching gas is filled in a filling container, the gas phase in the filling container has a carbonyl fluoride concentration of 100 mass ppm or less, and in the etching step, the gas phase may be extracted from the filling container and brought into contact with a member to be etched to etch the member.

[0059] [Pressure conditions for etching process] The pressure conditions for the etching step in the etching method according to this embodiment are not particularly limited, but are preferably 10 Pa or less, and more preferably 5 Pa or less. If the pressure conditions are within the above range, plasma can be easily generated stably. On the other hand, the pressure conditions for the etching step are preferably 0.05 Pa or more. If the pressure conditions are within the above range, a large number of ionized ions are generated, making it easy to obtain a sufficient plasma density. The flow rate of the etching gas may be appropriately set depending on the size of the chamber and the capacity of the exhaust equipment for reducing the pressure inside the chamber so that the pressure inside the chamber is kept constant.

[0060] [Temperature conditions for etching process] The temperature conditions for the etching step in the etching method according to this embodiment are not particularly limited, but are preferably 200° C. or less to obtain high etching selectivity, more preferably 150° C. or less to further prevent etching of non-etching targets such as masks, and even more preferably 100° C. or less to perform anisotropic etching. Here, the temperature in the temperature conditions refers to the temperature of the member to be etched, but the temperature of a stage that supports the member to be etched and is installed in the chamber of the etching apparatus can also be used.

[0061] The fluorobutene hardly reacts with non-etching objects, such as masks, at temperatures of 200°C or less. Therefore, when a member to be etched is etched using the etching method of this embodiment, the etching object can be selectively etched without substantially etching the non-etching object. Therefore, the etching method of this embodiment can be used in, for example, a method of processing a silicon-containing etching object into a predetermined shape by using a patterned non-etching object as a resist or mask.

[0062] Furthermore, if the temperatures of the etching object and the non-etching object are 200° C. or less, the etching selectivity tends to be high. For example, the etching selectivity, which is the ratio of the etching rate of the silicon-containing etching object to the etching rate of the non-etching object, tends to be 10 or more.

[0063] The bias power that constitutes the potential difference between the plasma generated during etching and the member to be etched may be selected from 0 to 10,000 W depending on the desired etching shape, and when selective etching is performed, it is preferably about 0 to 1,000 W. This potential difference allows anisotropic etching to be performed.

[0064] [Material to be etched] The member to be etched by the etching method according to this embodiment has an etching target and a non-etching target, but may be a member having a portion formed of an etching target and a portion formed of a non-etching target, or may be a member formed of a mixture of an etching target and a non-etching target. Furthermore, the member to be etched may have something other than an etching target and a non-etching target.

[0065] The shape of the member to be etched is not particularly limited, and may be, for example, a plate, foil, film, powder, or lump. An example of the member to be etched is the semiconductor substrate described above.

[0066] [Object to be etched] The object to be etched may be made of only a silicon-containing material, may have a portion made of only a silicon-containing material and a portion made of another material, or may be made of a mixture of a silicon-containing material and another material. Examples of silicon-containing materials include silicon oxide, silicon nitride, polysilicon, and silicon germanium (SiGe).

[0067] An example of silicon oxide is silicon dioxide (SiO2). Silicon nitride refers to a compound containing silicon and nitrogen in any ratio, and an example thereof is Si3N4. The purity of silicon nitride is not particularly limited, but is preferably 30% by mass or more, more preferably 60% by mass or more, and even more preferably 90% by mass or more. The shape of the object to be etched is not particularly limited, and may be, for example, a plate, foil, film, powder, or lump.

[0068] [Objects not to be etched] The non-etching target is a target that does not substantially react with the fluorobutene or reacts extremely slowly with the fluorobutene, so that etching hardly progresses even when etching is performed by the etching method according to this embodiment. The non-etching target is not particularly limited as long as it has the above-mentioned properties, but examples include photoresist, amorphous carbon (C), titanium nitride (TiN), metals such as copper (Cu), nickel (Ni), and cobalt (Co), as well as oxides and nitrides of these metals. Among these, photoresist and amorphous carbon are more preferred from the viewpoints of ease of handling and availability.

[0069] Photoresist refers to a photosensitive composition whose physical properties, including solubility, change when exposed to light or an electron beam. Examples include photoresists for g-line, h-line, i-line, KrF, ArF, F2, and EUV. The composition of the photoresist is not particularly limited as long as it is one commonly used in semiconductor manufacturing processes, but examples include compositions containing a polymer synthesized from at least one monomer selected from linear olefin, cyclic olefin, styrene, vinylphenol, acrylic acid, methacrylate, epoxy, melamine, and glycol.

[0070] Furthermore, the non-etching object can be used as a resist or mask to suppress etching of the etching object by the etching gas. Therefore, the etching method according to the present embodiment can be used in a method of processing the etching object into a predetermined shape (for example, processing a film-like etching object of a member to be etched to a predetermined film thickness) by using the patterned non-etching object as a resist or mask, and is therefore suitable for use in the manufacture of semiconductor elements. Furthermore, since the non-etching object is hardly etched, etching of portions of the semiconductor element that should not be etched can be suppressed, and the loss of characteristics of the semiconductor element due to etching can be prevented.

[0071] The non-etched material remaining after patterning can be removed by a removal method commonly used in semiconductor device manufacturing processes, such as ashing using oxidizing gases such as oxygen plasma or ozone, or dissolution removal using chemicals such as APM (ammonia water and hydrogen peroxide solution), SPM (sulfuric acid and hydrogen peroxide solution), or organic solvents.

[0072] Next, an example of the configuration of an etching apparatus capable of carrying out the etching method according to this embodiment and an example of an etching method using the etching apparatus will be described with reference to Figure 1. The etching apparatus in Figure 1 is a plasma etching apparatus that performs etching using plasma. First, the etching apparatus in Figure 1 will be described.

[0073] 1 includes a chamber 10 in which etching takes place, a plasma generator (not shown) that generates plasma inside the chamber 10, a stage 11 that supports a member 12 to be etched inside the chamber 10, a thermometer 14 that measures the temperature of the member 12 to be etched, an exhaust pipe 13 that exhausts gas from the chamber 10, a vacuum pump 15 that is connected to the exhaust pipe 13 and reduces the pressure inside the chamber 10, and a pressure gauge 16 that measures the pressure inside the chamber 10. If the stage 11 is connected to a high-frequency power source, it can be given the function of applying high-frequency waves to the member 12 to be etched.

[0074] The type of plasma generation mechanism of the plasma generator is not particularly limited, and may be one that applies a high-frequency voltage to parallel plates or one that passes a high-frequency current through a coil. When a high-frequency voltage is applied to the member 12 to be etched in the plasma, a negative voltage is applied to the member 12 to be etched, and positive ions are incident on the member 12 to be etched at high speed and perpendicularly, making anisotropic etching possible.

[0075] 1 also includes an etching gas supply unit that supplies an etching gas into chamber 10. This etching gas supply unit includes a fluorobutene gas supply unit 1 that supplies fluorobutene gas, a dilution gas supply unit 2 that supplies a dilution gas, a fluorobutene gas supply pipe 5 that connects fluorobutene gas supply unit 1 and chamber 10, and a dilution gas supply pipe 6 that connects dilution gas supply unit 2 to an intermediate portion of fluorobutene gas supply pipe 5.

[0076] Furthermore, the fluorobutene gas supply pipe 5 is provided with a fluorobutene gas pressure control device 7 that controls the pressure of the fluorobutene gas, and a fluorobutene gas flow rate control device 3 that controls the flow rate of the fluorobutene gas. Furthermore, the dilution gas supply pipe 6 is provided with a dilution gas pressure control device 8 that controls the pressure of the dilution gas, and a dilution gas flow rate control device 4 that controls the flow rate of the dilution gas. Note that equipment for supplying an additive gas may also be provided in the same configuration as the dilution gas supply unit 2, dilution gas flow rate control device 4, dilution gas supply pipe 6, and dilution gas pressure control device 8 (not shown).

[0077] When fluorobutene gas is supplied to chamber 10 as an etching gas, the interior of chamber 10 is depressurized with vacuum pump 15, and then fluorobutene gas is sent from fluorobutene gas supply unit 1 to fluorobutene gas supply pipe 5, so that the fluorobutene gas is supplied to chamber 10 via fluorobutene gas supply pipe 5.

[0078] Furthermore, when a mixed gas of fluorobutene gas and a diluent gas such as an inert gas is supplied as the etching gas, the inside of chamber 10 is depressurized by vacuum pump 15, and then fluorobutene gas is sent from fluorobutene gas supply unit 1 to fluorobutene gas supply pipe 5, and diluent gas is sent from diluent gas supply unit 2 to fluorobutene gas supply pipe 5 via diluent gas supply pipe 6. As a result, fluorobutene gas and diluent gas are mixed in the middle of fluorobutene gas supply pipe 5 to form a mixed gas, and this mixed gas is supplied to chamber 10 via fluorobutene gas supply pipe 5. However, fluorobutene gas and diluent gas may be supplied separately to chamber 10 and then formed into a mixed gas within chamber 10.

[0079] The configurations of the fluorobutene gas supply unit 1 and the diluent gas supply unit 2 are not particularly limited, and may be, for example, a gas tank or a cylinder. Furthermore, the fluorobutene gas flow rate control device 3 and the diluent gas flow rate control device 4 may be, for example, a mass flow controller or a flow meter.

[0080] When the etching gas is supplied to the chamber 10, it is preferable to supply the etching gas while maintaining the supply pressure of the etching gas (i.e., the value of the fluorobutene gas pressure control device 7 in FIG. 1) at a predetermined value. That is, the supply pressure of the etching gas is preferably 1 Pa or more and 0.2 MPa or less, more preferably 10 Pa or more and 0.1 MPa or less, and even more preferably 50 Pa or more and 50 kPa or less. When the supply pressure of the etching gas is within the above range, the etching gas is smoothly supplied to the chamber 10, and the load on the components of the etching apparatus of FIG. 1 (for example, the various devices and piping) is small.

[0081] Furthermore, from the viewpoint of uniformly etching the surface of the member to be etched 12, the pressure of the etching gas supplied into the chamber 10 is preferably from 1 Pa to 80 kPa, more preferably from 10 Pa to 50 kPa, and even more preferably from 100 Pa to 20 kPa. If the pressure of the etching gas in the chamber 10 is within the above range, a sufficient etching rate can be obtained and the etching selectivity ratio is likely to be high.

[0082] The pressure in the chamber 10 before the etching gas is supplied is not particularly limited as long as it is equal to or lower than the supply pressure of the etching gas. For example, -5 The pressure is preferably 1 Pa or more but less than 10 kPa, and more preferably 1 Pa or more but less than 2 kPa.

[0083] The differential pressure between the supply pressure of the etching gas and the pressure inside the chamber 10 before the etching gas is supplied is preferably 0.5 MPa or less, more preferably 0.3 MPa or less, and even more preferably 0.1 MPa or less. If the differential pressure is within the above range, the etching gas is likely to be smoothly supplied to the chamber 10.

[0084] The etching gas is preferably supplied while maintaining the temperature of the etching gas at a predetermined value when being supplied to the chamber 10. That is, the supply temperature of the etching gas is preferably 0°C or higher and 150°C or lower.

[0085] The etching processing time (hereinafter sometimes referred to as "etching time") can be set arbitrarily depending on the degree to which the etching target of the member to be etched 12 is desired to be etched, but considering the production efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes, more preferably within 40 minutes, and even more preferably within 20 minutes. Note that the etching processing time refers to the time during which the etching gas is in contact with the member to be etched 12 inside the chamber 10.

[0086] The etching method according to this embodiment can be performed using a general plasma etching apparatus used in the semiconductor device manufacturing process, such as the etching apparatus shown in FIG. 1, and the configuration of the etching apparatus that can be used is not particularly limited.

[0087] For example, the positional relationship between the fluorobutene gas supply pipe 5 and the member to be etched 12 is not particularly limited as long as it allows the etching gas to come into contact with the member to be etched 12. Furthermore, the configuration of the temperature adjustment mechanism of the chamber 10 is also sufficient as long as it is possible to adjust the temperature of the member to be etched 12 to a desired temperature. Therefore, the temperature adjustment mechanism for the member to be etched 12 may be directly provided on the stage 11, or an external temperature adjuster may be used to heat or cool the chamber 10 from outside the chamber 10.

[0088] 1 may be made of any material that is resistant to corrosion by the fluorobutene used and that can reduce the pressure to a predetermined level. For example, metals such as nickel, nickel-based alloys, aluminum, stainless steel, platinum, copper, and cobalt, ceramics such as alumina (Al2O3), and fluororesins may be used for the parts that come into contact with the etching gas.

[0089] Specific examples of nickel-based alloys include Inconel (registered trademark), Hastelloy (registered trademark), Monel (registered trademark), etc. Specific examples of fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), Viton (registered trademark), Kalrez (registered trademark), etc. [Example]

[0090] The present invention will be explained in more detail below with reference to examples and comparative examples. Fluorobutenes containing impurities such as carbonyl fluoride and hydrogen fluoride at various concentrations were prepared. Examples of the preparation of fluorobutenes are described below.

[0091] (Preparation Example 1) 1,1,1,4,4,4-Hexafluoro-2-butene filled in a 10 L manganese steel vessel was prepared.

[0092] The gas phase of 1,1,1,4,4,4-hexafluoro-2-butene was extracted from the manganese steel vessel and the oxygen concentration was measured, which was 1103 ppm by mass.The liquid phase of 1,1,1,4,4,4-hexafluoro-2-butene was extracted from the manganese steel vessel and the water concentration was measured, which was 384 ppm by mass.

[0093] The oxygen concentration was measured using a gas chromatograph GC-2014 manufactured by Shimadzu Corporation. The water concentration was measured using a Karl Fischer moisture analyzer CA-310 manufactured by Mitsubishi Chemical Analytech Corporation.

[0094] Next, the 1,1,1,4,4,4-hexafluoro-2-butene was subjected to a dehydration treatment as follows. A 1 L stainless steel SUS316 cylinder was filled with 100 mL of molecular sieve 3A manufactured by Union Showa Co., Ltd. and sealed. The cylinder was heated while reducing the pressure inside, and then cooled to -78°C. 500 g of 1,1,1,4,4,4-hexafluoro-2-butene was transferred from the manganese steel container to the cooled cylinder, and the 1,1,1,4,4,4-hexafluoro-2-butene was brought into contact with the molecular sieve 3A for dehydration treatment.

[0095] After the temperature of this cylinder was returned to room temperature, it was left standing for 24 hours in a room controlled at 20°C. After leaving it standing, the liquid phase was extracted from the cylinder and the water concentration of 1,1,1,4,4,4-hexafluoro-2-butene was measured, and it was found to be 2 ppm by mass. The water concentration was measured in the same manner as described above.

[0096] Next, the 1,1,1,4,4,4-hexafluoro-2-butene dehydrated as described above was subjected to deoxygenation gas treatment as described below using a purification apparatus equipped with a stainless steel distillation column, a 5 L kettle, a condenser, a distillate receiver, etc. 500 g of the 1,1,1,4,4,4-hexafluoro-2-butene dehydrated as described above was charged into the kettle, which was heated to 30°C and distilled. The stainless steel distillation column used was filled with laboratory packing manufactured by Sulzer ChemTech and had 10 theoretical plates. The condenser temperature was set to -40°C.

[0097] When the temperature at the top of the distillation column reached -40°C, 50 g of the fraction was withdrawn into a receiver. Then, the distillation was stopped, and the gas phase of 1,1,1,4,4,4-hexafluoro-2-butene remaining in the vessel was withdrawn and the oxygen concentration was measured, which was 4 ppm by mass. The oxygen concentration was measured in the same manner as described above.

[0098] Next, a 1 L SUS316 cylinder (hereinafter referred to as "cylinder A") was prepared. 400 g of 1,1,1,4,4,4-hexafluoro-2-butene remaining in the kettle of the refining apparatus after the deoxygenation gas treatment was filled into this cylinder A by gas-phase filling (filling step). Then, this cylinder A was left standing in a room controlled at 20°C for 30 days. The 1,1,1,4,4,4-hexafluoro-2-butene in cylinder A after being left standing for 30 days was designated Sample 1-1.

[0099] The gas phase of 1,1,1,4,4,4-hexafluoro-2-butene in Sample 1-1 was extracted from Cylinder A and the carbonyl fluoride concentration was measured, which was found to be less than 10 ppm by mass. The carbonyl fluoride concentration was measured using a Nicolet iS10 infrared spectrophotometer manufactured by Thermo Fisher Scientific K.K.

[0100] Next, three 500 mL cylinders made of SUS316 were prepared (hereinafter referred to as "cylinder B," "cylinder C," and "cylinder D"), and 100 g of 1,1,1,4,4,4-hexafluoro-2-butene was transferred from the manganese steel container to cylinders B, C, and D, respectively (filling process). Cylinder B was then left to stand for 10 days, cylinder C for 20 days, and cylinder D for 30 days in a room controlled at 20°C.

[0101] The 1,1,1,4,4,4-hexafluoro-2-butene in cylinder B after standing is designated sample 1-2, the 1,1,1,4,4,4-hexafluoro-2-butene in cylinder C after standing is designated sample 1-3, and the 1,1,1,4,4,4-hexafluoro-2-butene in cylinder D after standing is designated sample 1-4.

[0102] The gas phase portion of 1,1,1,4,4,4-hexafluoro-2-butene in Sample 1-2 was extracted from Cylinder B and the concentration of carbonyl fluoride was measured, which was found to be 211 ppm by mass.

[0103] Similarly, the gas phase portion of 1,1,1,4,4,4-hexafluoro-2-butene of Sample 1-3 was extracted from Cylinder C, and the concentrations of carbonyl fluoride and hydrogen fluoride were measured. The carbonyl fluoride concentration was 408 ppm by mass, and the hydrogen fluoride concentration was 392 ppm by mass. The hydrogen fluoride concentration was measured using a Nicolet iS10 infrared spectrophotometer manufactured by Thermo Fisher Scientific K.K.

[0104] Similarly, the gas phase portion of 1,1,1,4,4,4-hexafluoro-2-butene in Sample 1-4 was extracted from Cylinder D and the concentration of carbonyl fluoride was measured, which was found to be 589 ppm by mass.

[0105] (Preparation Example 2) 1,1,1,2,4,4,4-heptafluoro-2-butene was packed in a 10 L manganese steel vessel. The gas phase of 1,1,1,2,4,4,4-heptafluoro-2-butene was extracted from the vessel and the oxygen concentration was measured, which was 1225 ppm by mass. The liquid phase of 1,1,1,2,4,4,4-heptafluoro-2-butene was extracted from the vessel and the water concentration was measured, which was 382 ppm by mass. The water concentration and oxygen concentration were measured in the same manner as described above.

[0106] Samples 2-1 to 2-4 were prepared in the same manner as in Preparation Example 1, except that 1,1,1,2,4,4,4-heptafluoro-2-butene was used as the fluorobutene. The concentrations of carbonyl fluoride in each sample and hydrogen fluoride in sample 2-3 were measured using the same method as described above.

[0107] The carbonyl fluoride concentration of Sample 2-1 was less than 10 ppm by mass. The carbonyl fluoride concentration of Sample 2-2 was 268 ppm by mass. The carbonyl fluoride concentration of Sample 2-3 was 478 ppm by mass, and the hydrogen fluoride concentration was 155 ppm by mass. The carbonyl fluoride concentration of Sample 2-4 was 653 ppm by mass.

[0108] (Preparation Example 3) 2,3,3,4,4,4-Hexafluoro-1-butene filled in a 10 L manganese steel vessel was prepared. The gas phase of 2,3,3,4,4,4-hexafluoro-1-butene was extracted from the manganese steel vessel and the oxygen concentration was measured, which was 1313 mass ppm. Furthermore, the liquid phase of 2,3,3,4,4,4-hexafluoro-1-butene was extracted from the manganese steel vessel and the water concentration was measured, which was 411 mass ppm. The water concentration and oxygen concentration were measured in the same manner as described above.

[0109] Samples 3-1 to 3-4 were prepared in the same manner as in Preparation Example 1, except that 2,3,3,4,4,4-hexafluoro-1-butene was used as the fluorobutene. The concentrations of carbonyl fluoride in each sample and hydrogen fluoride in sample 3-3 were measured using the same method as described above.

[0110] The carbonyl fluoride concentration of Sample 3-1 was less than 10 ppm by mass. The carbonyl fluoride concentration of Sample 3-2 was 235 ppm by mass. The carbonyl fluoride concentration of Sample 3-3 was 411 ppm by mass, and the hydrogen fluoride concentration was 408 ppm by mass. The carbonyl fluoride concentration of Sample 3-4 was 603 ppm by mass.

[0111] (Preparation Example 4) 1,1,3,3,4,4,4-Heptafluoro-1-butene was packed in a 10 L manganese steel vessel. The gas phase of 1,1,3,3,4,4,4-heptafluoro-1-butene was extracted from the vessel and the oxygen concentration was measured, which was 1003 ppm by mass. The liquid phase of 1,1,3,3,4,4,4-heptafluoro-1-butene was extracted from the vessel and the water concentration was measured, which was 391 ppm by mass. The water and oxygen concentrations were measured in the same manner as described above.

[0112] Samples 4-1 to 4-4 were prepared in the same manner as in Preparation Example 1, except that 1,1,3,3,4,4,4-heptafluoro-1-butene was used as the fluorobutene. The concentrations of carbonyl fluoride in each sample and hydrogen fluoride in sample 4-3 were measured using the same method as described above.

[0113] The carbonyl fluoride concentration of Sample 4-1 was less than 10 ppm by mass. The carbonyl fluoride concentration of Sample 4-2 was 268 ppm by mass. The carbonyl fluoride concentration of Sample 4-3 was 437 ppm by mass, and the hydrogen fluoride concentration was 36 ppm by mass. The carbonyl fluoride concentration of Sample 4-4 was 622 ppm by mass. The concentrations of carbonyl fluoride and hydrogen fluoride in each sample are shown in Table 1.

[0114] [Table 1]

[0115] Example 1 A test specimen was prepared by forming a 1000 nm thick silicon oxide film, a 1000 nm thick silicon nitride film, and a 1000 nm thick photoresist film on the surface of a semiconductor wafer without laminating them, each of which was exposed on the surface. The test specimen was then etched using 1,1,1,4,4,4-hexafluoro-2-butene (Sample 1-1).

[0116] The etching equipment used was an ICP etching system RIE-230iP manufactured by Samco Inc. Specifically, 1,1,1,4,4,4-hexafluoro-2-butene (sample 1-1) at a flow rate of 10 mL / min and argon at a flow rate of 40 mL / min were introduced into the chamber independently and mixed in the chamber to prepare an etching gas. A high-frequency voltage of 500 W was applied to convert the etching gas into plasma in the chamber. The specimen in the chamber was then etched under the etching conditions of a pressure of 3 Pa, a temperature of 20°C, and a bias power of 100 W. The concentrations of carbonyl fluoride and hydrogen fluoride in the argon used here were measured, and neither was detected.

[0117] After etching was completed, the specimens were removed from the chamber, and the thicknesses of the silicon oxide film, silicon nitride film, and photoresist film were measured to calculate the thickness loss from pre-etching. The etching rate of each film was calculated by dividing this loss by the etching time. The etching rate of the photoresist film was found to be less than 1 nm / min, that of the silicon oxide film was 43 nm / min, and that of the silicon nitride film was 51 nm / min. These results confirmed that the silicon oxide and silicon nitride films, which are the etching targets, are selectively etched compared to the photoresist film, which is the non-etching target.

[0118] Example 2 The test specimens were etched in the same manner as in Example 1, except that 1,1,1,4,4,4-hexafluoro-2-butene of Sample 1-2 was used instead of Sample 1-1, and the etching rate of each film was calculated.

[0119] The results showed that the etching rate for the photoresist film was 2 nm / min, that for the silicon oxide film was 47 nm / min, and that for the silicon nitride film was 53 nm / min. These results confirmed that the silicon oxide film and silicon nitride film, which are the etching targets, are selectively etched compared to the photoresist film, which is the non-etching target.

[0120] Example 3 The test specimens were etched in the same manner as in Example 1, except that 1,1,1,4,4,4-hexafluoro-2-butene of Sample 1-3 was used instead of Sample 1-1, and the etching rate of each film was calculated.

[0121] The results showed that the etching rate for the photoresist film was 5 nm / min, that for the silicon oxide film was 55 nm / min, and that for the silicon nitride film was 59 nm / min. These results confirmed that the silicon oxide film and silicon nitride film, which are the etching targets, are selectively etched compared to the photoresist film, which is the non-etching target.

[0122] (Comparative Example 1) The test specimens were etched in the same manner as in Example 1, except that 1,1,1,4,4,4-hexafluoro-2-butene of Sample 1-4 was used instead of Sample 1-1, and the etching rate of each film was calculated.

[0123] The results showed that the etching rates for the photoresist film were 18 nm / min, the silicon oxide film 61 nm / min, and the silicon nitride film 64 nm / min. These results confirmed that the etching selectivity of the silicon oxide film and silicon nitride film, which are the etching targets, to the photoresist film, which is the non-etching target, decreased.

[0124] Example 4 A 0.5-inch diameter, 10-cm long stainless steel tube was filled with 10 mL of Union Showa Molecular Sieve 5A. Cylinder B, containing 1,1,1,4,4,4-hexafluoro-2-butene (Sample 1-2) after 10 days of standing, was connected to the SUS tube filled with Molecular Sieve 5A. 1,1,1,4,4,4-hexafluoro-2-butene (Sample 1-2) was passed from cylinder B to the SUS tube at a flow rate of 100 mL / min. The concentrations of carbonyl fluoride and hydrogen fluoride in the 1,1,1,4,4,4-hexafluoro-2-butene that passed through the inside of the SUS tube and exited the outlet were measured. The measurement method was the same as described above. As a result, both the carbonyl fluoride and hydrogen fluoride concentrations were less than 10 ppm by mass.

[0125] Next, the outlet of the SUS tube was connected to the reaction chamber of an etching apparatus, and etching similar to that in Example 1 was carried out while introducing 1,1,1,4,4,4-hexafluoro-2-butene, which had passed through the inside of the SUS tube and emerged from the outlet, into the reaction chamber.

[0126] The results showed that the etching rate of the photoresist film was less than 1 nm / min, that of the silicon oxide film was 44 nm / min, and that of the silicon nitride film was 53 nm / min. These results confirmed that the silicon oxide film and silicon nitride film, which are the etching targets, are selectively etched compared to the photoresist film, which is the non-etching target.

[0127] (Examples 5 to 13 and Comparative Examples 2 to 4) Except for using the samples shown in Table 2 instead of Sample 1-1, the test specimens were etched in the same manner as in Example 1, and the etching rate of each film was calculated. The results are shown in Table 2.

[0128] [Table 2]

[0129] The results of the above examples show that when the concentration of carbonyl fluoride in the etching gas is low, the etching target is selectively etched compared to the non-etching target, resulting in an etching selectivity ratio of 10 or more. On the other hand, the results of the above comparative examples show that when the concentration of carbonyl fluoride in the etching gas is high, the etching selectivity of the etching target relative to the non-etching target decreases, resulting in an etching selectivity ratio of less than 10. [Explanation of symbols]

[0130] 1. Fluorobutene gas supply unit 2. Dilution gas supply section 3. Fluorobutene gas flow control device 4. Dilution gas flow control device 5. Fluorobutene gas supply pipe 6. Dilution gas supply pipe 7. Fluorobutene gas pressure control device 8. Dilution gas pressure control device 10. Chamber 11 Stage 12. Material to be etched 13 Exhaust piping 14...Thermometer 15. Vacuum pump 16. Pressure gauge

Claims

1. General formula C 4 H x F y wherein x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8, An etching gas containing carbonyl fluoride as an impurity, the concentration of carbonyl fluoride being 100 mass ppm or less.

2. 2. The etching gas according to claim 1, further containing hydrogen fluoride as an impurity, the hydrogen fluoride concentration being 100 ppm by mass or less.

3. 3. A method for producing the etching gas according to claim 1 or 2, comprising: a dehydration step of subjecting the crude fluorobutene containing water and oxygen gas to a dehydration treatment; a deoxidizing step of subjecting the crude fluorobutene to a deoxidizing gas treatment; An etching gas manufacturing method comprising:

4. 4. The method for producing an etching gas according to claim 3, wherein the dehydration step is followed by the deoxidation step.

5. 5. The method for producing an etching gas according to claim 3, wherein the dehydration treatment is a treatment in which the crude fluorobutene is brought into contact with an adsorbent to adsorb water onto the adsorbent.

6. 6. The method for producing an etching gas according to claim 3, further comprising a filling step of filling a filling container with the fluorobutene that has been subjected to the dehydration step and the deoxidation step.

7. 3. An etching method comprising: an etching step of contacting the etching gas according to claim 1 or 2 with a member to be etched, the member having an etching object that is a target for etching by the etching gas and a non-etching object that is not a target for etching by the etching gas, and selectively etching the etching object compared to the non-etching object, wherein the etching object contains silicon.

8. 8. The etching method according to claim 7, wherein the etching gas is filled in a filling container, the gas phase in the filling container has a carbonyl fluoride concentration of 100 mass ppm or less, and in the etching step, the gas phase is extracted from the filling container and brought into contact with the member to be etched to etch the member to be etched.

9. 9. The etching method according to claim 7, wherein the etching gas is a mixed gas containing the fluorobutene and a dilution gas.

10. 10. The etching method according to claim 9, wherein the dilution gas is at least one gas selected from the group consisting of nitrogen gas, helium, argon, neon, krypton, and xenon.

11. A method for manufacturing a semiconductor element, comprising the steps of: manufacturing a semiconductor element by using the etching method according to any one of claims 7 to 10; the member to be etched is a semiconductor substrate having the etching object and the non-etching object, A method for manufacturing a semiconductor device, comprising a processing step of removing at least a part of the etching object from the semiconductor substrate by etching.

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