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

Abstract

Provided are an etching gas that can selectively etch an etching object containing silicon compared to a non-etching object, and an etching method. The etching gas contains a fluorine-containing hydrocarbon represented by the general formula C4H x F y x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x + y is 8. Also, the etching gas contains hydrogen fluoride as an impurity, and the concentration of the hydrogen fluoride is 100 mass ppm or less. The etching method includes an etching step in which the etching gas is brought into contact with an etched member (12) having an etching object and a non-etching object, and the etching object, which is an etching object of the etching gas, is selectively etched compared to the non-etching object, which is not an etching object of the etching gas. The etching object contains silicon.

Description

Technical Field

[0001] This invention relates to etching gases and their manufacturing methods, etching methods, and methods for manufacturing semiconductor devices. Background Technology

[0002] In semiconductor manufacturing processes, dry etching can be used for patterning and removing silicon compounds such as silicon oxide and silicon nitride. Dry etching requires high etch selectivity; that is, it must be able to selectively etch the silicon compound compared to the resists and masks used for patterning.

[0003] Various etching gases that meet this requirement have been proposed. For example, Patent Document 1 discloses an etching gas composed of hexafluorobutene. In addition, Patent Document 2 discloses an etching gas containing hexafluorobutene and hexafluorobutyne.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 6257638

[0007] Patent Document 2: Japanese Patent Publication No. 6462699 Summary of the Invention

[0008] However, when etching is performed using the etching gases disclosed in Patent Documents 1 and 2, there are cases where the etching selectivity becomes insufficient.

[0009] The present invention addresses the problem of providing an etching gas capable of selectively etching the etchable object compared to the non-etchable object when etching is performed by contacting an etching gas with an etchable object having an etchable object that is an etchable gas and a non-etchable object that is not an etchable gas, as well as an etching method and a semiconductor device manufacturing method thereof.

[0010] In order to solve the above-mentioned problems, one aspect of the present invention is shown in [1] to

[11] below.

[0011] [1] An etching gas containing the general formula C4H x F y The term represents fluorobutene in the general formula where x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8.

[0012] The etching gas contains hydrogen fluoride as an impurity, and the concentration of hydrogen fluoride is below 100 ppm by mass.

[0013] [2] The etching gas according to [1] also contains carbonyl fluoride as an impurity, and the concentration of carbonyl fluoride is less than 100 ppm by mass.

[0014] [3] A method for manufacturing an etching gas, comprising a dehydration step and a deoxygenation step, wherein the etching gas described in [1] or [2] is prepared.

[0015] In the dehydration process, the crude fluorobutene, which contains water and oxygen, undergoes dehydration treatment.

[0016] In the deoxygenation process, the crude fluorobutene is subjected to deoxygenation treatment.

[0017] [4] According to the method for manufacturing etching gas described in [3], the deoxygenation process is performed after the dehydration process.

[0018] [5] According to the method for manufacturing etching gas described in [3] or [4], the dehydration treatment is a process in which the crude fluorobutene is brought into contact with the adsorbent so that the adsorbent adsorbs water.

[0019] [6] The method for manufacturing etching gas according to any one of [3] to [5] further includes a filling step in which the fluorobutene that has undergone the dehydration step and the deoxygenation step is filled into a filling container.

[0020] [7] An etching method comprising an etching step in which an etching gas described in [1] or [2] is brought into contact with an etchable component having an etchable object and a non-etchable object, and the etchable object is selectively etched compared to the non-etchable object, wherein the etchable object is the etchable target of the etching gas and the non-etchable object is not the etchable target of the etching gas, and the etchable object contains silicon.

[0021] [8] According to the etching method described in [7], the etching gas is filled into a filling container, the concentration of hydrogen fluoride in the gas phase of the filling container is less than 100 ppm by mass, and in the etching process, the gas phase is extracted from the filling container and brought into contact with the etched component to etch the etched object.

[0022] [9] According to the etching method described in [7] or [8], the etching gas is a gas consisting only of the fluorobutene, or a mixture of the fluorobutene and a diluent gas.

[0023]

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

[0024]

[11] A method for manufacturing a semiconductor device, comprising manufacturing the semiconductor device using any one of the etching methods described in [7] to

[10] ,

[0025] The etched component is a semiconductor substrate having the etched object and the non-etched object.

[0026] The manufacturing method includes a processing step in which at least a portion of the object to be etched is removed from the semiconductor substrate by etching.

[0027] According to the present invention, it is possible to selectively etch silicon-containing objects compared to non-etched objects. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating an example of an etching apparatus for one embodiment of the etching method involved in the present invention. Detailed Implementation

[0029] The following describes one embodiment of the present invention. Furthermore, this embodiment illustrates one example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and the methods obtained by implementing such modifications or improvements are also included in the present invention.

[0030] The etching gas involved in this embodiment is a gas containing the general formula C4H. x F y The etching gas for fluorobutene, in which x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8, contains hydrogen fluoride (HF) as an impurity, with a concentration of HF of 100 ppm by mass or less.

[0031] The etching method according to this embodiment includes an etching step in which the etching gas described in this embodiment is brought into contact with a component having an etchable object and a non-etchable object, and the etchable object is selectively etched compared to the non-etchable object. The etchable object is the target of the etching gas, and the non-etchable object is not the target of the etching gas. Furthermore, in the etching method according to this embodiment, the etchable object contains silicon (Si).

[0032] When the etching gas comes into contact with the component to be etched, the silicon-containing material to be etched reacts with the fluorobutylene in the etching gas, thus etching of the material to be etched occurs. In contrast, non-materials to be etched, such as masks, hardly react with the fluorobutylene, thus etching of the non-materials to be etched hardly occurs. Therefore, according to the etching method of this embodiment, the material to be etched can be etched selectively compared to the non-materials to be etched (i.e., high etching selectivity can be obtained).

[0033] Furthermore, the aforementioned fluorobutene reacts and polymerizes during dry etching, and the non-etchable object is coated with this polymer film, thus protecting it during etching. Therefore, etching of the non-etchable object becomes more difficult, and if an etching gas containing the aforementioned fluorobutene is used for etching, the etching selectivity becomes even higher.

[0034] However, hydrogen fluoride is highly reactive to both the etchable materials (such as silicon oxide and silicon nitride) and the non-etchable materials (such as masks). Therefore, when etching components using an etching gas containing hydrogen fluoride, both the etchable and non-etchable materials are etched, risking insufficient etching selectivity. Therefore, to improve etching selectivity, it is necessary to reduce the concentration of hydrogen fluoride in the etching gas.

[0035] That is, the concentration of hydrogen fluoride in the etching gas needs to be set to 100 ppm by mass or less, preferably 50 ppm by mass or less, and more preferably 10 ppm by mass or less. If an etching gas with a hydrogen fluoride concentration within the above range is used for etching, the non-etchable object is difficult to etch, thus increasing the etching selectivity of the etchable object relative to the non-etchable object. There is no particular limitation on the method for determining the concentration of hydrogen fluoride; for example, it can be quantified using infrared spectrophotometry.

[0036] Furthermore, carbonyl fluoride (COF2) exhibits the same properties as hydrogen fluoride, showing high reactivity towards both etchable materials such as silicon oxide and silicon nitride, and non-etchable materials such as masks. Therefore, a low concentration of carbonyl fluoride in the etching gas is preferred. Specifically, when the etching gas also contains carbonyl fluoride as an impurity, the concentration of carbonyl fluoride in the etching gas is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and even more preferably 10 ppm by mass or less. The method for determining the concentration of carbonyl fluoride is not particularly limited; for example, quantification can be performed using infrared spectroscopy.

[0037] As described above, the etching gas involved in this embodiment has a low concentration of hydrogen fluoride. Therefore, if the etching gas involved in this embodiment is used for dry etching of the etched component, the non-etchable object is difficult to be etched, and the etchable object can be selectively etched compared to the non-etchable object, resulting in higher etching selectivity.

[0038] For example, the etch selectivity ratio, i.e., the ratio of the etching rate of the object to be etched to the etching rate of the non-object to be etched, is preferably 10 or more. The etch selectivity ratio is preferably 10 or more, more preferably 30 or more, and even more preferably 50 or more.

[0039] Carbonyl fluoride and hydrogen fluoride are impurities originating from the aforementioned fluorobutene. The following explains why carbonyl fluoride and hydrogen fluoride are commonly found as impurities in the aforementioned fluorobutene.

[0040] The aforementioned fluorobutenes often contain small amounts of oxygen (O2) and water (H2O). However, when the oxygen concentration in the fluorobutene exceeds 1000 ppm by mass, as shown in the following formula, the fluorobutene reacts with oxygen to produce carbonyl fluoride and hydrogen fluoride. Furthermore, the presence of water in the fluorobutene promotes the reaction shown in the following formula.

[0041] C4H x F y +(4-(yx) / 4)O2→(yx) / 2COF2+xHF+(4-(yx) / 2)CO2

[0042] The fluorobutene reacts with oxygen as described above to produce carbonyl fluoride and hydrogen fluoride. Therefore, in manufacturing the etching gas according to this embodiment, which contains the fluorobutene described above, it is necessary to remove water and oxygen from the fluorobutene in order to reduce the concentration of carbonyl fluoride and hydrogen fluoride.

[0043] That is, the etching gas manufacturing method according to this embodiment includes a dehydration step and a deoxygenation step. In the dehydration step, the aforementioned fluorobutene, i.e., crude fluorobutene, containing water and oxygen, is subjected to dehydration treatment. In the deoxygenation step, the crude fluorobutene is subjected to deoxygenation treatment. There is no particular limitation on the order of performing the dehydration step and the deoxygenation step; either step can be performed first. In addition, if possible, the dehydration step and the deoxygenation step can be performed simultaneously.

[0044] Furthermore, etching in this invention means: removing part or all of the etched object of the etched component and processing the etched component into a specified shape (e.g., a three-dimensional shape) (e.g., processing the etched component into a film-like etched object composed of silicon compound into a specified film thickness).

[0045] The etching method described in this embodiment can be used in the manufacture of semiconductor devices. That is, the semiconductor device manufacturing method described in this embodiment is a semiconductor device manufacturing method that uses the etching method described in this embodiment to manufacture semiconductor devices. The etched component is a semiconductor substrate having an etchable object and a non-etchable object. The manufacturing method includes a processing step of removing at least a portion of the etchable object from the semiconductor substrate by etching.

[0046] The etching method described in this embodiment can etch the object with high precision, and therefore can be used, for example, in the manufacture of semiconductor devices such as 3D-NAND flash memory and logic devices. Furthermore, the etching method described in this embodiment is expected to contribute to further miniaturization and high integration of semiconductor devices.

[0047] The etching gas, the method for manufacturing the etching gas, the etching method, and the method for manufacturing semiconductor devices involved in this embodiment are further described in detail below.

[0048] [Fluorobutylene]

[0049] The fluorobutene contained in the etching gas involved in this embodiment is formulated with the general formula C4H. x F y It is indicated that, and, satisfies the three conditions 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. There are no particular restrictions on the type of fluorobutene if the above conditions are met; both linear and branched fluorobutene (isobutene) can be used, but fluoro-1-butene and its analogues and fluoro-2-butene and its analogues are preferred.

[0050] As specific examples of fluoro-1-butene, 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-CH2-CH=CHF, CF3-CH2-CF=CH2, CF3-CHF-CH=CH2, CH3-CH2-CF=CF2, CH3-CHF-CH=CF2, CH3-CHF-CF=CHF, CH3-CF2-CH=CHF, CH3-CF2-CF=CH2, CH2F-CH2-CH=CF2, CH2F-CH2-CF=CHF, CH2F-CHF-CH=CHF, CH2F-CHF-CF=CH2, CH2F-CF2-CH=CH2, CHF2-CH2-CH=CHF, CHF2-CH2-CF=CH2, CHF2-CHF-CH=CH2, CF3-CH2-CH=CH2, CH3-CH2-CH=CF2, CH3-CH2-CF=CHF, CH3-CHF-CH=CHF, CH3-CHF-CF=CH2, CH3-CF2-CH=CH2, CH2F-CH2-CH=CHF, CH2F-CH2-CF=CH2, CH2F-CHF-CH=CH2, CHF2-CH2-CH=CH2CH3-CH2-CH=CHF, CH3-CH2-CF=CH2, CH3-CHF-CH=CH2, CH2F-CH2-CH=CH2. ,

[0051] Specific examples of fluorine-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=C. F-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, CH 2F-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.

[0052] These fluorobutenes can be used alone or in combination of two or more. In addition, some of the above-mentioned fluorobutenes exist as cis-trans isomers, but any cis- or trans-fluorobutenes can be used in the etching gas involved in this embodiment.

[0053] Among the aforementioned fluorobutenes, fluorobutenes with a boiling point of 50°C or less at 1 atmosphere are preferred, and fluorobutenes with a boiling point of 40°C or less at 1 atmosphere are more preferred. If the boiling point is within the above range, when fluorobutene gas is introduced into, for example, a plasma etching apparatus, the fluorobutene gas is difficult to liquefy inside the piping or other parts through which the fluorobutene gas is introduced. Therefore, malfunctions caused by the liquefaction of the fluorobutene gas can be suppressed, thus enabling efficient plasma etching processing.

[0054] [Etching Gas]

[0055] The etching gas is a gas containing the aforementioned fluorobutene. The etching gas can be a gas consisting solely of the aforementioned fluorobutene, or it can be a mixture of the aforementioned fluorobutene and a diluent gas. The diluent gas is preferably inactive relative to the fluorobutene and the component being etched. Alternatively, it can be a mixture of the aforementioned fluorobutene, the diluent gas, and an additive gas.

[0056] As a diluent gas, an inert gas is preferred, specifically, at least one selected from nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe) can be used.

[0057] As additive gases, fluorocarbon gases and hydrofluorocarbon gases can be used, for example. Specific examples of fluorocarbons include carbon tetrafluoride (CF4), 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 can be used alone, or two or more can be used in combination.

[0058] The content of the diluent gas, relative to the total amount of the etching gas, is preferably 90% by volume or less, more preferably 50% by volume or less. Furthermore, the content of the additive gas, relative to the total amount of the etching gas, is preferably 50% by volume or less, more preferably 30% by volume or less.

[0059] From the viewpoint of increasing the etching rate, the content of the aforementioned fluorobutene is preferably 5% by volume or more, and more preferably 10% by volume or more, relative to the total amount of etching gas. Furthermore, from the viewpoint of suppressing the amount of fluorobutene used, it is preferably 90% by volume or less, and more preferably 80% by volume or less, relative to the total amount of etching gas.

[0060] [Method for manufacturing etching gas]

[0061] The etching gas manufacturing method of this embodiment, as described above, includes a dehydration step and a deoxygenation step. In the dehydration step, the crude fluorobutene containing water and oxygen is subjected to dehydration treatment. In the deoxygenation step, the crude fluorobutene is subjected to deoxygenation treatment.

[0062] There are no particular limitations on the dehydration treatment method for removing water from crude fluorobutene, and known methods can be used. For example, a treatment that involves contacting the crude fluorobutene with an adsorbent can be employed. By contacting the crude fluorobutene with the adsorbent, the adsorbent adsorbs water, thus achieving dehydration. Furthermore, by contacting the crude fluorobutene with an adsorbent, sometimes at least one of carbonyl fluoride and hydrogen fluoride can be removed from the crude fluorobutene along with water.

[0063] The type of adsorbent is not particularly limited as long as it can remove water from the aforementioned fluorobutene; examples include molecular sieve 3A, molecular sieve 4A, molecular sieve 5A, activated carbon, and silica gel. Among these exemplified adsorbents, molecular sieve 3A, which is capable of selectively adsorbing water, is more preferred.

[0064] Furthermore, the aforementioned molecular sieves can be used as adsorbents for removing carbonyl fluoride. Additionally, the aforementioned molecular sieves, metal fluorides such as sodium fluoride, can be used as adsorbents for removing hydrogen fluoride.

[0065] When contacting crude fluorobutene with the adsorbent, either gaseous or liquid fluorobutene can be used. Furthermore, the contact between crude fluorobutene and the adsorbent can be carried out in a flow-through or batch manner. However, to minimize the moisture concentration in the fluorobutene, it is more preferable to use a method that involves intermittently contacting liquid fluorobutene with the adsorbent for at least 24 hours.

[0066] By dehydration treatment, the water concentration in the above-mentioned fluorobutene is preferably 500 ppm by mass or less, more preferably 100 ppm by mass or less, and even more preferably 10 ppm by mass or less. If this is the case, the formation of carbonyl fluoride and hydrogen fluoride by the reaction described above is unlikely to occur.

[0067] There are no particular limitations on the method for determining the moisture concentration in the aforementioned fluorobutene; for example, the Karl Fischer method can be used for quantification.

[0068] There are no particular limitations on the deoxygenation treatment method for removing oxygen from crude fluorobutene. For example, oxygen can be separated by distillation of the crude fluorobutene. Furthermore, by distilling the crude fluorobutene, at least one of carbonyl fluoride and hydrogen fluoride may sometimes be removed from the crude fluorobutene along with oxygen.

[0069] There are no particular limitations on the distillation method as long as it can separate oxygen from crude fluorobutene; for example, batch distillation or continuous distillation can be used. There are no particular limitations on the form of the distillation column used in the distillation; for example, plate columns using sieve trays, bubble cap trays, etc., or packed columns filled with regular or irregular packing materials can be used.

[0070] There are no particular limitations on distillation conditions, but the theoretical plate number is preferably 1 or more and 30 or less, more preferably 3 or more and 10 or less.

[0071] There is no particular limitation on the temperature of the bottom (bottle) of the distillation column into which crude fluorobutene is loaded during distillation, but it is preferably set to 10°C or higher and 80°C or lower, and more preferably 20°C or higher and 60°C or lower.

[0072] There is no particular limitation on the temperature at the top of the distillation column, but it is preferably set to above -60°C and below 0°C, and more preferably above -50°C and below -20°C.

[0073] By performing a deoxygenation treatment, the oxygen concentration in the fluorobutene is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, and even more preferably 100 ppm by mass or less. In this case, the formation of carbonyl fluoride and hydrogen fluoride through the reaction described above is unlikely to occur.

[0074] There are no particular limitations on the method for determining the oxygen concentration in the aforementioned fluorobutene; for example, gas chromatography can be used for quantification.

[0075] Furthermore, the etching gas manufacturing method according to this embodiment may also include a filling step, in which the above-mentioned fluorobutene, which has undergone a dehydration step and a deoxygenation step to reduce the oxygen and water content, is filled into a filling container.

[0076] When the etching gas is a mixture containing the aforementioned fluorobutene and diluent gas, the mixture can be filled into a filling container after the fluorobutene and diluent gas are mixed to form a mixture, or the fluorobutene and diluent gas can be filled into the filling container separately to form a mixture within the filling container.

[0077] There are no particular limitations on the method for filling the filling container with the aforementioned fluorobutene; for example, gas-phase filling or liquid-phase filling methods can be used. Additionally, oxygen in the filling container can be removed before filling with fluorobutene using methods such as heating and vacuuming.

[0078] There are no particular restrictions on the material of the filling container; for example, manganese steel, stainless steel, Hastelloy (a registered trademark), and Inconel (a registered trademark) can be listed.

[0079] [Etching Method]

[0080] The etching described in this embodiment can be achieved using either plasma etching or plasma-free etching. Examples of plasma etching include reactive ion etching (RIE), inductively coupled plasma (ICP), capacitively coupled plasma (CCP), electron cyclotron resonance (ECR) plasma etching, and microwave plasma etching.

[0081] Furthermore, in plasma etching, the plasma can be generated within the chamber containing the component to be etched, or the plasma generation chamber can be separate from the chamber containing the component to be etched (i.e., remote plasma can also be used). By using remote plasma etching, it is sometimes possible to etch silicon-containing objects with higher selectivity.

[0082] Furthermore, in the etching method described in this embodiment, etching gas filled into a filling container can also be used for etching. That is, etching gas can be filled into a filling container, the concentration of hydrogen fluoride in the gas phase of the filling container is 100 ppm by mass or less, and in the etching process, the gas phase is extracted from the filling container and brought into contact with the component to be etched to etch the object.

[0083] [Pressure conditions for the etching process]

[0084] The pressure conditions of the etching process in the etching method of this embodiment are not particularly limited, but are preferably set to 10 Pa or less, more preferably 5 Pa or less. If the pressure conditions are within the above range, it is easy to generate plasma stably. On the other hand, the pressure conditions of the etching process are preferably 0.05 Pa or more. If the pressure conditions are within the above range, more ionized ions are generated, and it is easy to obtain sufficient plasma density.

[0085] The flow rate of the etching gas can be appropriately set according to the size of the chamber and the capacity of the exhaust equipment for depressurizing the chamber, so that the pressure in the chamber remains constant.

[0086] [Temperature conditions for the etching process]

[0087] The temperature conditions for the etching process in the etching method described in this embodiment are not particularly limited, but in order to obtain high etching selectivity, it is preferable to set it to 200°C or below. In order to further suppress the etching of non-etchable objects such as masks, it is more preferable to set it to 150°C or below. In order to perform anisotropic etching, it is even more preferable to set it to 100°C or below. Here, the temperature of the temperature condition is the temperature of the component being etched, but the temperature of the stage that supports the component being etched and is provided in the chamber of the etching apparatus can also be used.

[0088] The aforementioned fluorobutene hardly reacts with non-etchable objects such as masks at temperatures below 200°C. Therefore, if the etching method according to this embodiment is used to etch the component to be etched, the etchable object can be selectively etched without etching the non-etchable object. Therefore, the etching method according to this embodiment can be used in methods such as using a patterned non-etchable object as a resist or mask to process silicon-containing etchable objects into a predetermined shape.

[0089] Furthermore, if the temperature of both the object to be etched and the object not to be etched is below 200°C, the etching selectivity tends to be high. For example, the ratio of the etching rate of the silicon-containing object to the etching rate of the object not to be etched, i.e., the etching selectivity, tends to be 10 or higher.

[0090] Regarding the bias power that constitutes the potential difference between the plasma generated during etching and the etched component, it can be selected from 0 to 10000 W according to the desired etching shape, and is preferably around 0 to 1000 W in the case of selective etching. Anisotropic etching can be performed using this potential difference.

[0091] [Etched component]

[0092] The etched component etched using the etching method according to this embodiment has an etchable object and a non-etchable object, but it can be a component having a portion formed by the etchable object and a portion formed by the non-etchable object, or it can be a component formed by a mixture of the etchable object and the non-etchable object. Furthermore, the etched component may also have portions other than the etchable object and the non-etchable object.

[0093] Furthermore, the shape of the etched component is not particularly limited; it can be, for example, plate-shaped, foil-shaped, film-shaped, powder-shaped, or block-shaped. As an example of the etched component, the aforementioned semiconductor substrate can be cited.

[0094] [Object to be etched]

[0095] The object to be etched can be an object formed solely of a silicon-containing material, an object having portions formed solely of a silicon-containing material and portions formed of other materials, or an object formed of a mixture of a silicon-containing material and other materials. Examples of silicon-containing materials include silicon oxide, silicon nitride, polysilicon, and silicon-germanium (SiGe).

[0096] Examples of silicon oxide include silicon dioxide (SiO2). Silicon nitride refers to compounds containing silicon and nitrogen in any proportion; for example, 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.

[0097] In addition, there are no particular limitations on the shape of the object being etched; it can be, for example, plate-shaped, foil-shaped, film-shaped, powder-shaped, or block-shaped.

[0098] [Non-etched objects]

[0099] The non-etchable material does not react substantially with the aforementioned fluorobutylene, or reacts with it very slowly. Therefore, even when etched using the etching method described in this embodiment, etching is hardly performed. The non-etchable material is not particularly limited as long as it possesses the properties described above; examples include photoresists, amorphous carbon (C), titanium nitride (TiN), copper (Cu), nickel (Ni), cobalt (Co), and other metals, as well as oxides and nitrides of these metals. From the viewpoint of operability and ease of acquisition, photoresists and amorphous carbon are more preferred.

[0100] Photoresist refers to a photosensitive composition whose physical properties, primarily solubility, change due to light, electron beams, etc. Examples include photoresists for g-line, h-line, i-line, KrF, ArF, F2, and EUV applications. The composition of a photoresist is not particularly limited if it is a composition commonly used in semiconductor manufacturing processes; for example, compositions containing polymers synthesized from at least one monomer selected from linear olefins, cyclic olefins, styrene, vinylphenol, acrylic acid, methacrylates, epoxy, melamine, and glycols can be included.

[0101] Furthermore, the non-etched object can be used as a resist or mask to suppress the etching of the etched object by the etching gas. Therefore, the etching method according to this embodiment can be used to process the etched object into a specified shape (e.g., to process the film-like etched object of the etched component into a specified film thickness) by using the patterned non-etched object as a resist or mask, and thus can be suitable for the manufacture of semiconductor devices. In addition, since the non-etched object is hardly etched, it is possible to suppress the etching of parts of the semiconductor device that should not be etched, and to prevent the loss of semiconductor device characteristics due to etching.

[0102] Furthermore, any remaining non-etched material after patterning can be removed using removal methods commonly used in semiconductor device manufacturing processes. Examples include: ashing using oxidizing gases such as oxygen plasma or ozone; dissolution using solutions such as APM (a mixture of ammonia and hydrogen peroxide water), SPM (a mixture of sulfuric acid and hydrogen peroxide water), and organic solvents.

[0103] Next, refer to Figure 1 This section describes an example of the configuration of an etching apparatus capable of implementing the etching method described in this embodiment, and an example of an etching method using the etching apparatus. Figure 1 The etching apparatus is a plasma etching apparatus that uses plasma for etching. First, regarding... Figure 1 The etching apparatus will be described.

[0104] Figure 1 The etching apparatus includes: a chamber 10 for etching; a plasma generator (not shown) for generating plasma inside the chamber 10; a stage 11 supporting the etched component 12 inside the chamber 10; a thermometer 14 for measuring the temperature of the etched component 12; an exhaust pipe 13 for venting gas from inside the chamber 10; a vacuum pump 15 installed on the exhaust pipe 13 for depressurizing the pressure inside the chamber 10; and a pressure gauge 16 for measuring the pressure inside the chamber 10. If the stage 11 is connected to a high-frequency power supply, it can be equipped with the function of applying a high frequency to the etched component 12.

[0105] There is no particular limitation on the type of plasma generation mechanism of the plasma generator. It can be a plasma generation mechanism that applies a high-frequency voltage to a parallel plate, or a plasma generation mechanism that flows a high-frequency current in a coil. When a high-frequency voltage is applied to the etched component 12 in the plasma, a negative voltage is applied to the etched component 12, and positive ions are injected into the etched component 12 at high speed and perpendicularly, thus enabling anisotropic etching.

[0106] in addition, Figure 1 The etching apparatus includes an etching gas supply unit that supplies etching gas to the interior of the chamber 10. The etching gas supply unit includes a fluorobutene gas supply unit 1 for supplying fluorobutene gas, a dilution gas supply unit 2 for supplying dilution gas, a fluorobutene gas supply pipe 5 connecting the fluorobutene gas supply unit 1 to the chamber 10, and a dilution gas supply pipe 6 connecting the dilution gas supply unit 2 to the middle part of the fluorobutene gas supply pipe 5.

[0107] Furthermore, the fluorobutene gas supply pipe 5 is equipped with a fluorobutene gas pressure control device 7 for controlling the pressure of the fluorobutene gas and a fluorobutene gas flow control device 3 for controlling the flow rate of the fluorobutene gas. Similarly, the dilution gas supply pipe 6 is equipped with a dilution gas pressure control device 8 for controlling the pressure of the dilution gas and a dilution gas flow control device 4 for controlling the flow rate of the dilution gas. Moreover, a device for supplying additive gas (not shown) can also be attached in the same manner as the dilution gas supply unit 2, the dilution gas flow control device 4, the dilution gas supply pipe 6, and the dilution gas pressure control device 8.

[0108] Furthermore, when fluorobutene gas is supplied to the chamber 10 as an etching gas, after the internal pressure of the chamber 10 is reduced by using the vacuum pump 15, fluorobutene gas is sent from the fluorobutene gas supply unit 1 to the fluorobutene gas supply pipe 5, thereby fluorobutene gas is supplied to the chamber 10 via the fluorobutene gas supply pipe 5.

[0109] Alternatively, when a mixture of fluorobutene gas and a diluent gas such as an inert gas is supplied as the etching gas, the interior of the chamber 10 is depressurized using the vacuum pump 15. Then, fluorobutene gas is supplied from the fluorobutene gas supply section 1 to the fluorobutene gas supply pipe 5, and diluent gas is supplied from the diluent gas supply section 2 to the fluorobutene gas supply pipe 5 via the diluent gas supply pipe 6. Thus, in the middle section of the fluorobutene gas supply pipe 5, the fluorobutene gas and the diluent gas mix to form a mixed gas, which is then supplied to the chamber 10 via the fluorobutene gas supply pipe 5. However, it is also possible to supply the fluorobutene gas and the diluent gas separately to the chamber 10, forming a mixed gas within the chamber 10.

[0110] Furthermore, the configuration of the fluorobutene gas supply unit 1 and the dilution gas supply unit 2 is not particularly limited; for example, they can be gas cylinders, cylindrical containers, etc. Additionally, the fluorobutene gas flow control device 3 and the dilution gas flow control device 4 can be, for example, mass flow controllers, flow meters, etc.

[0111] When supplying etching gas to chamber 10, it is preferable to keep the supply pressure of the etching gas (i.e., Figure 1 The fluorobutene gas pressure control device 7 is maintained at a predetermined value while supplying the etching gas. Specifically, the supply pressure of the etching gas is preferably set to 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. If the supply pressure of the etching gas is within the above range, the etching gas can be smoothly supplied to the chamber 10, and for… Figure 1 The etching apparatus has components (e.g., the various devices and piping mentioned above) with low load.

[0112] Furthermore, from the viewpoint of uniformly etching the surface of the etched component 12, the pressure of the etching gas supplied to the chamber 10 is preferably 1 Pa or more and 80 kPa or less, more preferably 10 Pa or more and 50 kPa or less, and even more preferably 100 Pa or more and 20 kPa or less. 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 can easily become higher.

[0113] The pressure within chamber 10 before the etching gas is supplied is not particularly limited if it is below or lower than the supply pressure of the etching gas, but is preferably, for example, 10. -5 Pa or higher and less than 10 kPa, more preferably 1 Pa or higher and less than 2 kPa.

[0114] The pressure difference 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 pressure difference is within the above range, the supply of etching gas to the chamber 10 can be easily and smoothly carried out.

[0115] When supplying etching gas to chamber 10, it is preferable to supply the etching gas while maintaining its temperature at a predetermined value. That is, the supply temperature of the etching gas is preferably above 0°C and below 150°C.

[0116] The etching processing time (hereinafter sometimes referred to as "etching time") can be arbitrarily set according to the degree of etching of the etched object on the etched component 12, 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. Furthermore, the etching processing time refers to the time during which the etching gas comes into contact with the etched component 12 inside the chamber 10.

[0117] The etching method described in this embodiment can be used with, for example... Figure 1The etching is performed using a typical plasma etching apparatus used in semiconductor device manufacturing processes, similar to an etching apparatus. There are no particular limitations on the configuration of the etching apparatus that can be used.

[0118] For example, the positional relationship between the fluorobutene gas supply pipe 5 and the etched component 12 is not particularly limited as long as the etching gas can contact the etched component 12. Furthermore, regarding the configuration of the temperature control mechanism of the chamber 10, it is acceptable as long as the temperature of the etched component 12 can be adjusted to any desired temperature. Therefore, the temperature control mechanism of the etched component 12 can be directly mounted on the stage 11, or an external temperature controller can be used to heat or cool the chamber 10 from the outside.

[0119] in addition, Figure 1 The material of the etching apparatus is not particularly limited, as long as it is corrosion-resistant to the fluorobutylene used and can be depressurized to the specified pressure. For example, in the part that comes into contact with the etching gas, metals such as nickel, nickel-based alloys, aluminum, stainless steel, platinum, copper, and cobalt, ceramics such as alumina (Al2O3), and fluororesins can be used.

[0120] Specific examples of nickel-based alloys include Inconel (registered trademark), Hastelloy (registered trademark), and Monel (registered trademark). Similarly, examples of fluoropolymers include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), fluororubber (Viton (registered trademark)), and perfluorinated rubber (Kalrez (registered trademark)).

[0121] Example

[0122] The present invention will be described in more detail below with examples and comparative examples. Fluorobutene containing carbonyl fluoride and hydrogen fluoride as impurities in various concentrations was prepared. Examples of fluorobutene preparation are described below.

[0123] (Preparation Example 1)

[0124] 1,1,1,4,4,4-hexafluoro-2-butene was prepared and filled into a 10L manganese steel container.

[0125] The oxygen concentration was determined by extracting the gas phase of 1,1,1,4,4,4-hexafluoro-2-butene from a manganese steel container, and the result was 1103 ppm by mass. Additionally, the water concentration was determined by extracting the liquid phase of 1,1,1,4,4,4-hexafluoro-2-butene from the same manganese steel container, and the result was 384 ppm by mass.

[0126] Furthermore, oxygen concentration was measured using a GC-2014 gas chromatograph manufactured by Shimadzu Corporation. Additionally, moisture concentration was measured using a Karl Fischer CA-310 moisture analyzer from Mitsubishi Chemical Analytech Co., Ltd.

[0127] Next, the 1,1,1,4,4,4-hexafluoro-2-butene was dehydrated as follows: 100 mL of molecular sieve 3A manufactured by Union Showa Co., Ltd. was filled into a 1 L stainless steel SUS316 cylindrical container and sealed. The container was heated while the internal pressure was reduced, and then cooled to -78°C. 500 g of 1,1,1,4,4,4-hexafluoro-2-butene was transferred from a manganese steel container into the cooled cylindrical container, bringing the 1,1,1,4,4,4-hexafluoro-2-butene into contact with molecular sieve 3A for dehydration.

[0128] After the container was brought back to room temperature, it was left to stand for 24 hours in a room maintained at 20°C. Then, the liquid phase was extracted from the container after standing to determine the water concentration of 1,1,1,4,4,4-hexafluoro-2-butene, which was 2 ppm by mass. The method for determining the water concentration was the same as described above.

[0129] Next, for the 1,1,1,4,4,4-hexafluoro-2-butene that had undergone dehydration as described above, a purification apparatus equipped with a SUS distillation column, a 5L capacity kettle, a condenser, and a fraction receiver was used for deoxygenation treatment as follows. 500g of the dehydrated 1,1,1,4,4,4-hexafluoro-2-butene was added to the kettle, and distillation was performed by heating the kettle to 30°C. The SUS distillation column used was packed with laboratory packing manufactured by SulzerChemtech, and the theoretical plate number was set to 10. Furthermore, the temperature of the condenser was set to -40°C.

[0130] When the temperature at the top of the distillation column reaches -40°C, 50 g of the fraction is drawn into the receiver. Then, distillation is stopped, and the remaining vapor phase of 1,1,1,4,4,4-hexafluoro-2-butene in the vessel is drawn off to determine the oxygen concentration, which is 4 ppm by mass. The method for determining the oxygen concentration is the same as described above.

[0131] Next, a 1L SUS316 cylindrical container (hereinafter referred to as "Container A") was prepared. 400g of 1,1,1,4,4,4-hexafluoro-2-butene remaining in the refining apparatus after deoxygenation treatment was introduced into Container A via gas-phase filling (filling process). Container A was then left to stand for 30 days in a room maintained at 20°C. The 1,1,1,4,4,4-hexafluoro-2-butene remaining in Container A after 30 days of standing was taken as Sample 1-1.

[0132] The concentration of hydrogen fluoride was determined by extracting the gas phase of 1,1,1,4,4,4-hexafluoro-2-butene from container A. The result showed that the concentration of hydrogen fluoride was less than 10 ppm by mass. Furthermore, the concentration of hydrogen fluoride was measured using a Nicolet iS10 infrared spectrophotometer manufactured by Thermo Fisher Scientific Co., Ltd.

[0133] Next, prepare three 500mL SUS316 cylindrical containers (hereinafter referred to as "Container B", "Container C", and "Container D"). Transfer 100g of 1,1,1,4,4,4-hexafluoro-2-butene from the manganese steel container into each of these containers (filling process). Then, in a room maintained at 20°C, container B is left to stand for 10 days, container C for 20 days, and container D for 30 days.

[0134] The 1,1,1,4,4,4-hexafluoro-2-butene in container B after settling was taken as sample 1-2, the 1,1,1,4,4,4-hexafluoro-2-butene in container C after settling was taken as sample 1-3, and the 1,1,1,4,4,4-hexafluoro-2-butene in container D after settling was taken as sample 1-4.

[0135] The gas phase of 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-2 was extracted from container B to determine the concentration of hydrogen fluoride. The result showed that the concentration of hydrogen fluoride was 210 ppm by mass.

[0136] Similarly, the gas phase of samples 1-3 (1,1,1,4,4,4-hexafluoro-2-butene) extracted from container C was used to determine the concentrations of hydrogen fluoride and carbonyl fluoride. The results showed that the concentration of hydrogen fluoride was 392 ppm by mass and the concentration of carbonyl fluoride was 408 ppm by mass. Furthermore, the concentration of carbonyl fluoride was determined using a Nicolet iS10 infrared spectrophotometer manufactured by Solar Chemicals Co., Ltd.

[0137] Similarly, the gas phase of 1,1,1,4,4,4-hexafluoro-2-butene from samples 1-4 was extracted from container D to determine the concentration of hydrogen fluoride, and the result showed that the concentration of hydrogen fluoride was 588 ppm by mass.

[0138] (Preparation Example 2)

[0139] 1,1,1,4,4-pentafluoro-2-butene was prepared and filled into a 10 L manganese steel container. The gas phase of 1,1,1,4,4-pentafluoro-2-butene was extracted from the manganese steel container to determine the oxygen concentration, which was 1322 ppm by mass. Conversely, the liquid phase of 1,1,1,4,4-pentafluoro-2-butene was extracted from the manganese steel container to determine the water concentration, which was 399 ppm by mass. The methods for determining the water and oxygen concentrations were the same as described above.

[0140] Except that 1,1,1,4,4-pentafluoro-2-butene was used as the fluorobutene described above, samples 2-1 to 2-4 were prepared by performing the same operation as in Preparation Example 1. The concentrations of hydrogen fluoride in each sample and carbonyl fluoride in sample 2-3 were then determined. The determination method was the same as described above.

[0141] The concentration of hydrogen fluoride in sample 2-1 is less than 10 ppm by mass.

[0142] The concentration of hydrogen fluoride in sample 2-2 was 189 ppm by mass.

[0143] The concentration of hydrogen fluoride in samples 2-3 was 332 ppm by mass, and the concentration of carbonyl fluoride was 102 ppm by mass.

[0144] The concentration of hydrogen fluoride in samples 2-4 was 513 ppm by mass.

[0145] (Preparation Example 3)

[0146] 2,3,3,4,4,4-hexafluoro-1-butene was prepared and filled into a 10 L manganese steel container. The gas phase of 2,3,3,4,4,4-hexafluoro-1-butene was extracted from the manganese steel container to determine the oxygen concentration, which was 1313 ppm by mass. Conversely, the liquid phase of 2,3,3,4,4,4-hexafluoro-1-butene was extracted from the manganese steel container to determine the water concentration, which was 411 ppm by mass. The methods for determining the water and oxygen concentrations were the same as described above.

[0147] Except that 2,3,3,4,4,4-hexafluoro-1-butene was used as the fluorobutene described above, samples 3-1 to 3-4 were prepared by performing the same operation as in Preparation Example 1. The concentrations of hydrogen fluoride in each sample and carbonyl fluoride in sample 3-3 were then measured. The measurement method was the same as described above.

[0148] The concentration of hydrogen fluoride in sample 3-1 is less than 10 ppm by mass.

[0149] The concentration of hydrogen fluoride in sample 3-2 was 211 ppm by mass.

[0150] The concentration of hydrogen fluoride in sample 3-3 was 408 ppm by mass, and the concentration of carbonyl fluoride was 411 ppm by mass.

[0151] The concentration of hydrogen fluoride in samples 3-4 was 588 ppm by mass.

[0152] (Preparation Example 4)

[0153] 3,3,4,4,4-pentafluoro-1-butene was prepared and filled into a 10 L manganese steel container. The gas phase of 3,3,4,4,4-pentafluoro-1-butene was extracted from the manganese steel container to determine the oxygen concentration, which was 1103 ppm by mass. Conversely, the liquid phase of 3,3,4,4,4-pentafluoro-1-butene was extracted from the manganese steel container to determine the water concentration, which was 393 ppm by mass. The methods for determining the water and oxygen concentrations were the same as described above.

[0154] Except that 3,3,4,4,4-pentafluoro-1-butene was used as the fluorobutene described above, samples 4-1 to 4-4 were prepared by performing the same operation as in Preparation Example 1. Then, the concentrations of hydrogen fluoride in each sample and the concentration of carbonyl fluoride in sample 4-3 were determined. The determination method was the same as described above.

[0155] The concentration of hydrogen fluoride in sample 4-1 is less than 10 ppm by mass.

[0156] The concentration of hydrogen fluoride in sample 4-2 was 223 ppm by mass.

[0157] The concentration of hydrogen fluoride in sample 4-3 was 418 ppm by mass, and the concentration of carbonyl fluoride was 36 ppm by mass.

[0158] The concentration of hydrogen fluoride in sample 4-4 was 574 ppm by mass.

[0159] Furthermore, the concentrations of carbonyl fluoride and hydrogen fluoride in each sample are shown in Table 1.

[0160]

[0161] (Example 1)

[0162] On the surface of a semiconductor wafer, a silicon oxide film, a silicon nitride film, and a photoresist film with a thickness of 1000 nm are formed separately on the surface without being stacked, and this wafer is used as a test specimen. Then, the test specimen is etched using 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-1.

[0163] As the etching apparatus, a Samco RIE-230iP ICP etching system was used. Specifically, 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-1 was independently introduced into the chamber at a flow rate of 10 mL / min, and argon gas was introduced at a flow rate of 40 mL / min. The etching gases were mixed within the chamber to prepare the etching gas mixture. A high-frequency voltage of 500 W was applied to plasmaize the etching gas within the chamber. The test specimen was then etched within the chamber under etching conditions of 3 Pa pressure, 20 °C temperature, and 100 W bias power. Furthermore, the concentrations of carbonyl fluoride and hydrogen fluoride in the argon gas used were measured, and neither was detected.

[0164] After etching, the test specimen was removed from the chamber, and the thicknesses of the silicon oxide film, silicon nitride film, and photoresist film were measured. The reduction in thickness of each film relative to its original thickness before etching was calculated. The etching rate of each film was calculated by dividing this reduction by the etching time. The results showed that the etching rate of the photoresist film was less than 1 nm / min, the etching rate of the silicon oxide film was 43 nm / min, and the etching rate of the silicon nitride film was 51 nm / min. These results confirm that the silicon oxide and silicon nitride films, which were the targets of etching, were selectively etched compared to the photoresist film, which was not the object of etching.

[0165] (Example 2)

[0166] Except that 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-2 was used instead of sample 1-1, the etching of the test specimens was performed in the same manner as in Example 1, and the etching rate of each film was calculated.

[0167] As a result, the etching rate of the photoresist film was 2 nm / min, the etching rate of the silicon oxide film was 47 nm / min, and the etching rate of the silicon nitride film was 53 nm / min. This result confirms that, compared to the photoresist film, which is not the object of etching, the silicon oxide and silicon nitride films, which are the objects of etching, were selectively etched.

[0168] (Example 3)

[0169] Except that 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-3 was used instead of sample 1-1, the etching of the test specimens was performed in the same manner as in Example 1, and the etching rate of each film was calculated.

[0170] As a result, the etching rate of the photoresist film was 5 nm / min, the etching rate of the silicon oxide film was 55 nm / min, and the etching rate of the silicon nitride film was 59 nm / min. This result confirms that, compared to the photoresist film, which is not the object of etching, the silicon oxide and silicon nitride films, which are the objects of etching, were selectively etched.

[0171] (Comparative Example 1)

[0172] Except that 1,1,1,4,4,4-hexafluoro-2-butene from sample 1-4 was used instead of sample 1-1, the etching of the test specimens was performed in the same manner as in Example 1, and the etching rate of each film was calculated.

[0173] As a result, the etching rate of the photoresist film was 18 nm / min, the etching rate of the silicon oxide film was 61 nm / min, and the etching rate of the silicon nitride film was 64 nm / min. This result confirms that the etching selectivity of the silicon oxide and silicon nitride films, as the objects of etching, is reduced compared to that of the photoresist film, which is not the object of etching.

[0174] (Example 4)

[0175] 10 mL of molecular sieve 5A manufactured by Union Showa Co., Ltd. was filled into a 0.5-inch diameter, 10 cm long SUS tube. A cylindrical container B containing 1,1,1,4,4,4-hexafluoro-2-butene samples 1-2, after being left to stand for 10 days, was connected to the aforementioned SUS tube filled with molecular sieve 5A. The 1,1,1,4,4,4-hexafluoro-2-butene samples 1-2 were passed from container B into the SUS tube at a flow rate of 100 mL / min. The concentrations of hydrogen fluoride and carbonyl fluoride in the 1,1,1,4,4,4-hexafluoro-2-butene passing through the inside of the SUS tube and exiting through the outlet were then measured. The measurement method was the same as described above. The results showed that the concentrations of both hydrogen fluoride and carbonyl fluoride were less than 10 ppm by mass.

[0176] Next, the outlet of the SUS tube is connected to the reaction chamber of the etching apparatus, and 1,1,1,4,4,4-hexafluoro-2-butene, which passes through the inside of the SUS tube and exits from the outlet, is introduced into the reaction chamber while the same etching process as in Example 1 is performed.

[0177] As a result, the etching rate of the photoresist film was less than 1 nm / min, the etching rate of the silicon oxide film was 44 nm / min, and the etching rate of the silicon nitride film was 53 nm / min. This result confirms that, compared to the photoresist film, which is not the object of etching, the silicon oxide and silicon nitride films, which are the objects of etching, were selectively etched.

[0178] (Examples 5-13 and Comparative Examples 2-4)

[0179] Except that the sample described in Table 2 was used instead of sample 1-1, the etching of the test specimens was performed in the same manner as in Example 1, and the etching rate of each film was calculated. The results are shown in Table 2.

[0180]

[0181] As can be seen from the results of the above embodiments, when the concentration of hydrogen fluoride in the etching gas is low, the object to be etched is selectively etched compared to the non-etched object, and the etching selectivity is 10 or higher. On the other hand, as can be seen from the results of the above comparative examples, when the concentration of hydrogen fluoride in the etching gas is high, the etching selectivity of the object to be etched relative to the non-etched object decreases, and the etching selectivity becomes less than 10.

[0182] Explanation of reference numerals in the attached figures

[0183] 1…Fluorobutylene Gas Supply Department

[0184] 2…Dilution Gas Supply Department

[0185] 3…Fluorobutene gas flow control device

[0186] 4…Dilution gas flow control device

[0187] 5…Pipes for supplying fluorobutene gas

[0188] 6… Piping for dilution gas supply

[0189] 7…Fluorobutene gas pressure control device

[0190] 8…Dilution gas pressure control device

[0191] 10…chamber

[0192] 11...platform

[0193] 12…etched components

[0194] 13…Exhaust piping

[0195] 14…Thermometer

[0196] 15…vacuum pump

[0197] 16… Pressure gauge

Claims

1. An etching method comprising an etching step, wherein an etching gas is brought into contact with a component having an etchable object and a non-etchable object, and the etchable object is selectively etched compared to the non-etchable object, wherein the etchable object is the target of the etching gas, and the non-etchable object is not the target of the etching gas, and the etchable object contains silicon. The etching gas is composed solely of the general formula C4H. x F y The gas is defined as a gas composed of fluorobutene in which x is 1 or more and 7 or less, y is 1 or more and 7 or less, and x+y is 8; or a mixed gas composed of fluorobutene and a diluent gas; or a mixed gas composed of fluorobutene, a diluent gas, and an additive gas, wherein the diluent gas is at least one selected from nitrogen, helium, neon, argon, krypton, and xenon; and the additive gas is a fluorocarbon gas and / or a hydrofluorocarbon gas. The etching gas contains hydrogen fluoride as an impurity, with a concentration of less than 100 ppm by mass. The etching gas is obtained through a manufacturing method that includes dehydration and deoxygenation processes. In the dehydration process, the crude fluorobutene, which contains water and oxygen, undergoes dehydration treatment. In the deoxygenation process, the crude fluorobutene is subjected to deoxygenation treatment.

2. The etching method according to claim 1, wherein the etching gas further contains carbonyl fluoride as an impurity, and the concentration of carbonyl fluoride is below 100 ppm by mass.

3. The etching method according to claim 1 or 2, wherein the deoxygenation step is performed after the dehydration step in the method for producing the etching gas.

4. In the etching method according to claim 1 or 2, in the method for producing the etching gas, the dehydration treatment is a process of contacting the crude fluorobutene with an adsorbent to allow the adsorbent to adsorb water.

5. The etching method according to claim 1 or 2, wherein the method for manufacturing the etching gas further comprises a filling step, wherein the fluorobutene having undergone the dehydration step and the deoxygenation step is filled into a filling container.

6. The etching method according to claim 1 or 2, wherein the etching gas is filled into a filling container, the concentration of hydrogen fluoride in the gas phase of the filling container is less than 100 ppm by mass, and in the etching process, the gas phase is extracted from the filling container and brought into contact with the etched component to etch the etched object.

7. A method for manufacturing a semiconductor device, comprising using the etching method described in any one of claims 1 to 6 to manufacture the semiconductor device. The etched component is a semiconductor substrate having the etched object and the non-etched object. The manufacturing method includes a processing step in which at least a portion of the object to be etched is removed from the semiconductor substrate by etching.

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