Dry etching method, semiconductor device manufacturing method, and dry etching gas composition

Abstract

To provide a dry etching method capable of etching silicon oxide at a sufficient rate even at a lower temperature of 200°C or lower without generating a residue, a method of producing a semiconductor device using the dry etching method, and a dry etching gas composition.SOLUTION: A silicon oxide dry etching method includes reacting silicon oxide with: gaseous hydrogen fluoride and a gaseous organic amine compound; a hydrogen fluoride salt of a gaseous organic amine compound; or gaseous hydrogen fluoride, a gaseous organic amine compound, and a hydrogen fluoride salt of a gaseous organic amine compound. The organic amine compound is an organic amine mixture containing at least two compounds represented by the following general formula (1). R1-N=R2R3...(1) In the formula, R1 is a C1-C10 hydrocarbon group having a ring, a hetero atom, or a halogen atom, and R2 and R3 are each a hydrogen atom or a C1-C10 hydrocarbon group having a ring, a hetero atom, or a halogen atom.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a dry etching method for dry etching silicon oxide, a method for manufacturing a semiconductor device using the dry etching method, and a dry etching gas composition. [Background technology]

[0002] In the semiconductor device manufacturing process, there is a step to etch the silicon oxide film present on the surface of the semiconductor wafer, whether it is a CVD-based oxide film, a thermal oxide film, or a native oxide film. Methods for etching such silicon oxide films include wet etching using chemical solutions and plasma etching using reactive gas plasma.

[0003] However, wet etching had the problem that the chemical solution could easily cause adverse effects on components that were not being etched. Furthermore, plasma etching had the problem of causing electrical damage to the wafer due to the plasma.

[0004] To address these problems, methods for dry etching without using plasma have been attempted. For example, Patent Document 1 discloses a method for dry etching SiO2 without using plasma by adding gaseous water, Patent Document 2 discloses gaseous methanol, Patent Document 3 discloses gaseous acetic acid, and Patent Document 4 discloses gaseous isopropyl alcohol to hydrogen fluoride gas.

[0005] Furthermore, methods using a mixed gas containing hydrogen fluoride gas and ammonia gas have been investigated for high-speed etching of SiO2. For example, Patent Document 5 discloses a two-step etching method consisting of an AFS layer formation step (Chemical Oxide Removal; COR treatment) in which a mixed gas containing HF gas and NH3 gas is supplied to the surface of a silicon oxide film on a substrate, causing a chemical reaction between the silicon oxide film and the mixed gas to transform the silicon oxide film into ammonium silicofluoride (AFS), and this reaction product layer is formed on the silicon layer of the substrate; and a heating step (Post Heat Treatment; PHT treatment) in which the AFS layer is heated without supplying the mixed gas to sublimate or thermally decompose. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-181188 [Patent Document 2] Japanese Patent Application Publication No. 8-81788 [Patent Document 3] Special Publication No. 9-509531 [Patent Document 4] Special Publication No. 2001-503571 [Patent Document 5] Japanese Patent Publication No. 2007-180418 (Japanese Patent Publication No. 4890025) [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the methods described in Patent Documents 1 to 4 had problems such as insufficient etching rates for SiO2.

[0008] In the method described in Patent Document 5, if only COR treatment was performed, there was a problem that an AFS layer remained as a residue on the surface of the silicon oxide film. Further, when a thick AFS layer was formed in the COR treatment, in order to completely remove the AFS layer by the PHT treatment, it was necessary to heat to a temperature exceeding 200°C, and there was also concern about damage to members other than the silicon oxide film.

[0009] Furthermore, since it was necessary to increase the treatment temperature during PHT treatment compared to COR treatment, there was a problem that the chamber needed to be heated and cooled every time the process was switched, or the chamber needed to be separated for each process, which was a factor in reducing productivity.

[0010] In view of the above problems, an object of the present disclosure is to provide a dry etching method capable of etching silicon oxide at a sufficient rate even at a low temperature of 200°C or lower without generating residues, a method for manufacturing a semiconductor device using the dry etching method, a dry etching gas composition, and the like.

Means for Solving the Problems

[0011] As a result of intensive studies, the present inventors have found that even when an organic amine compound is used as a base instead of NH3, silicon oxide reacts with HF and the organic amine compound, and the sublimation temperature of the reaction product is significantly lower than that of ammonium fluorosilicate, so the reaction product can be removed at a low temperature, and by using at least two types of organic amine compounds, the etching rate of silicon oxide is further increased, and thus the present disclosure has been completed.

[0012] Specifically, the dry etching method of the present disclosure is a dry etching method of silicon oxide in which gaseous hydrogen fluoride, gaseous organic amine compound, hydrogen fluoride salt of gaseous organic amine compound, or gaseous hydrogen fluoride, gaseous organic amine compound, and hydrogen fluoride salt of gaseous organic amine compound are reacted with silicon oxide, The above organic amine compound is characterized by being an organic amine mixture containing at least two compounds represented by the following general formula (1). [Chemical Formula] (In general formula (1), N is a nitrogen atom. R

[0013] , 1 ,

[0015] , , 2 , , 3 , 2 , , 2 , , , 3 ,

[0014] , 1 , is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. R 2 , R 3 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. However, when the hydrocarbon group has 3 or more carbon atoms, it may have a branched-chain structure or a cyclic structure. The heteroatom of the hydrocarbon group is a nitrogen atom, an oxygen atom, a sulfur atom, or a phosphorus atom. Further, when both R 1 and R 2 are hydrocarbon groups having 1 or more carbon atoms, R 1 and R 2 may be directly bonded to form a cyclic structure. Further, when R 1 or R 2 is directly bonded by a double bond to form a cyclic structure, R 3 may not be present and an aromatic ring may be formed. Also, R 1 , R 2 and R 3 may be the same hydrocarbon group or different hydrocarbon groups.)

[0013] In the dry etching method of the present disclosure, the above organic amine mixture can be reacted with silicon oxide, and dry etching of silicon oxide can be performed at a faster rate than in the conventional case.

[0014] In the dry etching method of the present disclosure, it is desirable that the above organic amine mixture contains at least a secondary amine and a tertiary amine, and the composition ratio preferably contains 10 volume ppm to 10 volume % of the above secondary amine with respect to the total amount of the above tertiary amine and the above secondary amine.

[0015] In the dry etching method of this disclosure, if the organic amine mixture contains at least a secondary amine and a tertiary amine, and the composition ratio is such that the secondary amine is present in an amount of 10 volume ppm to 10 volume percent relative to the total amount of the tertiary amine and the secondary amine, then dry etching of silicon oxide can be performed at a faster rate.

[0016] In the dry etching method of this disclosure, it is preferable that the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, and dimethylethylamine, and it is more preferable that the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

[0017] In the dry etching method of this disclosure, when reacting silicon oxide with gaseous hydrogen fluoride and a mixture of gaseous organic amines, a hydrogen fluoride salt of the mixture of gaseous organic amines, or gaseous hydrogen fluoride, a mixture of gaseous organic amines, and a hydrogen fluoride salt of the mixture of gaseous organic amines, it is preferable to carry out the reaction without creating a plasma state.

[0018] Plasma etching refers to a process in which a halogen-based gas, such as one with a temperature of approximately 0.1 to 10 Torr, is introduced into a reactor, and high-frequency power is applied to an external coil or counter electrode to generate a low-temperature gas plasma within the reactor. This plasma then uses the activated halogen species to etch silicon oxide and other materials.

[0019] In the dry etching method of this disclosure, the above-mentioned organic amine mixture can be reacted without a plasma state, and dry etching of silicon oxide can be performed at a faster rate than in the conventional method without generating the above-mentioned gas plasma.

[0020] The method for manufacturing a semiconductor device according to this disclosure is characterized by including a step of etching a silicon oxide film on a semiconductor substrate having a silicon oxide film by applying the dry etching method described above.

[0021] The semiconductor device manufacturing method of this disclosure includes a step of etching the silicon oxide film by applying the above-described dry etching method to a semiconductor substrate having a silicon oxide film. Therefore, the silicon oxide film on the semiconductor substrate can be etched at a high speed, and the target semiconductor device can be manufactured quickly.

[0022] The dry etching gas composition of this disclosure is a dry etching gas composition comprising hydrogen fluoride and an organic amine mixture, wherein the organic amine mixture is an organic amine mixture comprising at least two compounds represented by the general formula (1) above.

[0023] Since the dry etching gas composition of this disclosure contains hydrogen fluoride and the above-mentioned organic amine mixture, dry etching of silicon oxide can be performed at a faster rate than in conventional cases.

[0024] The organic amine mixture of this disclosure is an organic amine mixture for use in the dry etching method described above, and is characterized by comprising at least two compounds represented by the general formula (1) above. [Effects of the Invention]

[0025] The dry etching method of this disclosure makes it possible to etch silicon oxide at a lower temperature of 200°C or below without generating residue, and at a faster rate than conventional methods. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a schematic diagram of a reaction apparatus, which is an example of an etching apparatus used in the dry etching method according to the embodiment of this disclosure. [Figure 2]Figure 2 is a graph showing the relationship between the concentration of amine 2 (amine 2 / (amine 1 + amine 2) (volume ppm)) and the etching amount when dimethylamine was used as amine 2 in Examples 1 to 3 and Comparative Examples 1 and 2. [Modes for carrying out the invention]

[0027] The present disclosure will be described in detail below, but the description of the constituent elements described below is an example of an embodiment of the present disclosure and is not limited to these specific contents. It can be implemented in various ways within the scope of its gist.

[0028] The dry etching method of the present disclosure is a method for dry etching silicon oxide by reacting silicon oxide with gaseous hydrogen fluoride and a gaseous organic amine compound, a hydrogen fluoride salt of a gaseous organic amine compound, or gaseous hydrogen fluoride, a gaseous organic amine compound and a hydrogen fluoride salt of a gaseous organic amine compound, The above organic amine compound is characterized by being an organic amine mixture containing at least two compounds represented by the following general formula (1). [ka] (In general formula (1), N is a nitrogen atom. R 1 R is a hydrocarbon group having 1 to 10 carbon atoms, which may contain rings, heteroatoms, or halogen atoms. 2 , R 3 This is a hydrocarbon group having a hydrogen atom or 1 to 10 carbon atoms, which may have a ring, heteroatom, or halogen atom. However, if the hydrocarbon group has 3 or more carbon atoms, it may have a branched chain structure or a cyclic structure. The heteroatom of the hydrocarbon group is a nitrogen atom, oxygen atom, sulfur atom, or phosphorus atom. Furthermore, R 1 and R 2 If both are hydrocarbon groups having 1 or more carbon atoms, R 1 and R 2 They may be directly bonded to form a cyclic structure. Furthermore, R 1 or R 2When R is directly bonded by a double bond to form a cyclic structure, 3 Aromatic rings may be formed even without the presence of R. 1 , R 2 and R 3 (These may be the same hydrocarbon group or different hydrocarbon groups.)

[0029] [First Embodiment] In the first embodiment, a mixture of gaseous hydrogen fluoride and at least two compounds represented by the general formula (1) is supplied to an etching apparatus and brought into contact with silicon oxide to dry etch the silicon oxide. That is, a process gas containing the hydrogen fluoride and the organic amine mixture, a process gas containing the hydrogen fluoride salt of the organic amine mixture, or a process gas containing the hydrogen fluoride, the organic amine mixture, and the hydrogen fluoride salt of the organic amine mixture is brought into contact with silicon oxide to dry etch the silicon oxide.

[0030] When silicon oxide is brought into contact with a treatment gas containing hydrogen fluoride and an organic amine mixture containing at least two compounds represented by the general formula (1) above, the silicon oxide undergoes a chemical reaction with the hydrogen fluoride and the organic amine mixture, transforming into reaction products such as an organic amine salt of hexafluorosilicic acid. The silicon oxide is removed when these reaction products are formed, either by sublimation into a gas or by thermal decomposition into a gas. In this disclosure, sublimation refers not only to the process of a solid turning into a gas without thermal decomposition, but also to the process of a solid turning into a gaseous component through thermal decomposition.

[0031] In the dry etching method of this disclosure, hydrogen fluoride gas and the organic amine mixture may be supplied separately as the processing gas and mixed in the etching apparatus, or hydrogen fluoride salts of multiple organic amines obtained by reacting hydrogen fluoride and the organic amine mixture in advance may be supplied as a gas to the etching apparatus. Even when hydrogen fluoride gas and the organic amine mixture are supplied separately and mixed in the etching apparatus, hydrogen fluoride salts of multiple organic amines are generated in at least a portion of the etching apparatus. Therefore, in the etching apparatus, three components—gasic hydrogen fluoride, gaseous organic amine mixture, and hydrogen fluoride salts of the organic amine mixture—may coexist and come into contact with the silicon oxide, or only the hydrogen fluoride salts of the organic amine mixture may come into contact with the silicon oxide, or only gaseous hydrogen fluoride and the organic amine mixture may come into contact with the silicon oxide. Ultimately, in all cases, the reaction with silicon oxide results in the formation of an organic amine salt of hexafluorosilicic acid.

[0032] The mixing ratio of hydrogen fluoride and organic amine mixture contained in the processed gas is preferably 0.001 to 100, more preferably 0.01 to 10, and particularly preferably 0.1 to 5, obtained by dividing the total number of moles of organic amine compounds contained in the organic amine mixture by the number of moles of hydrogen fluoride.

[0033] In the dry etching method of this disclosure, an organic amine mixture containing at least two compounds represented by the general formula (1) above can be used as the organic amine compound.

[0034] In the compound shown in general formula (1), R 1 Examples include methyl groups, ethyl groups, propyl groups, and butyl groups, and some of the hydrogen atoms constituting these organic groups may be substituted with halogens such as fluorine and chlorine. 2 and R 3Examples of these include hydrogen atoms, methyl groups, ethyl groups, propyl groups, and butyl groups, and some or all of the hydrogen atoms constituting these organic groups may be substituted with halogens such as fluorine and chlorine. The organic amine represented by the general formula (1) above may also be a heterocyclic amine having a five-membered ring structure or a six-membered ring structure.

[0035] Specific examples of compounds included in the above organic amine mixture include monomethylamine, dimethylamine, trimethylamine, dimethylethylamine, diethylmethylamine, monoethylamine, diethylamine, triethylamine, mononormal propylamine, ethylpropylamine, dinormal propylamine, monoisopropylamine, ethylisopropylamine, diisopropylamine, monobutylamine, dibutylamine, monotertiary butylamine, ditertiary butylamine, pyrrolidine, piperidine, piperazine, pyridine, and pyrazine. Other specific examples include compounds in which some or all of the CH bonds of the above compounds are replaced by CF bonds (trifluoromethylamine, 1,1,1-trifluorodimethylamine, perfluorodimethylamine, 2,2,2-trifluoroethylamine, perfluoroethylamine, bis(2,2,2-trifluoroethyl)amine, perfluorodiethylamine, and 3-fluoropyridine).

[0036] These compounds are preferred because their conjugate acid pKa is 3.2 or higher than that of HF (hydrogen fluoride), they can form salts with hydrogen fluoride, they have a constant vapor pressure in the temperature range of 20 to 100°C, and they do not decompose in this temperature range, allowing them to be supplied as a gas. By mixing at least two of these compounds, the organic amine mixture of this disclosure can be obtained.

[0037] In particular, due to their easy availability, the above compounds are preferably monomethylamine, dimethylamine, trimethylamine, triethylamine, monoethylamine, monopropylamine, ethylpropylamine, isopropylamine, ethylisopropylamine, 1,1,1-trifluorodimethylamine, 2,2,2-trifluoroethylamine, and bis(2,2,2-trifluoroethyl)amine, and it is preferable to mix at least two of these compounds to obtain the organic amine mixture of this disclosure.

[0038] Furthermore, secondary and tertiary amines are preferred as the above organic amine compounds due to their fast etching rate of silicon oxide. Specific examples of secondary amines include dimethylamine, diethylamine, ethylisopropylamine, ethylpropylamine, dinormalpropylamine, diisopropylamine, dibutylamine, and ditert-butylamine. Specific examples of tertiary amines include trimethylamine, dimethylethylamine, diethylmethylamine, and triethylamine.

[0039] The organic amine mixture of this disclosure is not particularly limited and may contain two, three or more of the organic amines represented by the general formula (1) described above. Specific combinations of organic amines constituting the organic amine mixture include trimethylamine and dimethylamine, trimethylamine and monomethylamine, trimethylamine and dimethylethylamine, trimethylamine, dimethylamine, monomethylamine, and dimethylethylamine, triethylamine and ethylisopropylamine, triethylamine and diethylamine, and the like. The organic amine mixture may also contain ammonia.

[0040] The composition ratio of the above organic amine mixture is preferably such that the secondary amine is present in an amount of 10 volume ppm to 10 volume% relative to the total amount of the tertiary amine and the secondary amine, and more preferably such that the secondary amine is present in an amount of 100 volume ppm to 5000 volume ppm relative to the total amount of the tertiary amine and the secondary amine.

[0041] In the dry etching method of this disclosure, it is preferable that the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, and dimethylethylamine, and it is even more preferable that the secondary amine is dimethylamine and the tertiary amine is trimethylamine. In this case, the organic amine mixture more preferably contains dimethylamine at a concentration of 10 ppm to 10% by volume relative to the total amount of trimethylamine and dimethylamine, and even more preferably contains dimethylamine at a concentration of 100 ppm to 5000 ppm by volume relative to the total amount of trimethylamine and dimethylamine.

[0042] The dry etching gas composition of this disclosure is a dry etching gas composition comprising hydrogen fluoride and an organic amine mixture, wherein the organic amine mixture is an organic amine mixture comprising at least two compounds represented by the following general formula (1). [ka] (In general formula (1), N is a nitrogen atom. R 1 R is a hydrocarbon group having 1 to 10 carbon atoms, which may contain rings, heteroatoms, or halogen atoms. 2 , R 3 This is a hydrocarbon group having a hydrogen atom or 1 to 10 carbon atoms, which may have a ring, heteroatom, or halogen atom. However, if the hydrocarbon group has 3 or more carbon atoms, it may have a branched chain structure or a cyclic structure. The heteroatom of the hydrocarbon group is a nitrogen atom, oxygen atom, sulfur atom, or phosphorus atom. Furthermore, R 1 and R 2 If both are hydrocarbon groups having 1 or more carbon atoms, R 1 and R 2 They may be directly bonded to form a cyclic structure. Furthermore, R 1 or R 2 When R is directly bonded by a double bond to form a cyclic structure,3 Aromatic rings may be formed even without the presence of R. 1 , R 2 and R 3 (These may be the same hydrocarbon group or different hydrocarbon groups.)

[0043] Furthermore, in the dry etching gas composition of this disclosure, the organic amine mixture preferably contains at least a secondary amine and a tertiary amine, more preferably the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, and dimethylethylamine, and even more preferably the secondary amine is dimethylamine and the tertiary amine is trimethylamine. The dry etching gas composition of this disclosure may consist substantially of hydrogen fluoride and the above-mentioned organic amine mixture. Furthermore, the dry etching gas composition may or may not contain an inert gas.

[0044] Furthermore, the composition ratio of the organic amine mixture constituting the dry etching gas composition is preferably such that the secondary amine is present in a ratio of 10 volume ppm to 10 volume% relative to the total amount of the tertiary amine and the secondary amine, and more preferably such that the secondary amine is present in a ratio of 100 volume ppm to 5000 volume ppm relative to the total amount of the tertiary amine and the secondary amine.

[0045] The inert gas is preferably at least one selected from the group consisting of N2, He, Ne, Ar, Kr, and Xe, with Ar and N2 being more preferred. The proportion of the inert gas contained in the dry etching gas composition is the value obtained by dividing the number of moles of the inert gas by the number of moles of hydrogen fluoride, which is preferably between 0 and 100, more preferably 10 or less, and particularly preferably 5 or less.

[0046] The contact temperature between the dry etching gas composition and the silicon oxide (temperature of the silicon oxide) should be above the temperature at which the reaction product of the silicon oxide, hydrogen fluoride, and organic amine mixture sublimes or decomposes. However, considering productivity and damage to the substrate being processed, the contact temperature is preferably 200°C or lower, more preferably 150°C or lower, and particularly preferably 120°C or lower. For example, the contact temperature is preferably 20°C or higher, more preferably 50°C or higher, and particularly preferably 80°C or higher.

[0047] The pressure at which the dry etching gas composition comes into contact with the silicon oxide is not particularly limited, but is preferably 0.1 Pa to 100 kPa, more preferably 0.5 Pa to 50 kPa, and particularly preferably 1 Pa to 10 kPa.

[0048] Furthermore, the temperature and pressure do not need to remain constant during contact between the dry etching gas composition and the silicon oxide; they may be changed at regular intervals. For example, periods of time may be set aside to increase the temperature or decrease the pressure to promote the sublimation of the reaction product.

[0049] Furthermore, as described in Patent Document 5, a COR step in which the dry etching gas composition is brought into contact with silicon oxide and a PHT step in which the reaction product is sublimated without supplying the dry etching gas composition may be performed. However, in this embodiment, the PHT step may be performed at 200°C or lower.

[0050] The method for manufacturing a semiconductor device according to this disclosure is characterized by including a step of etching a silicon oxide film on a semiconductor substrate having a silicon oxide film by applying the dry etching method described above. A semiconductor substrate is typically a silicon substrate, and in addition to a silicon oxide film, silicon films, silicon nitride films, metal films, etc., may be exposed on the semiconductor substrate.

[0051] In particular, by using the dry etching method of this embodiment on a substrate to be treated in which both a silicon oxide film and a silicon nitride film are exposed, the silicon oxide film can be selectively etched relative to the silicon nitride film. The (silicon oxide / silicon nitride) etching selectivity ratio is preferably 2.5 or higher, more preferably 5 or higher, even more preferably 8 or higher, and particularly preferably 10 or higher. The (silicon oxide / silicon nitride) etching selectivity ratio is the value obtained by dividing the etching rate of the silicon oxide film by the etching rate of the silicon nitride film. The etching rate is the value obtained by dividing the change in film thickness before and after etching by the time required for etching. Therefore, the higher the (silicon oxide / silicon nitride) etching selectivity ratio, the higher the proportion of silicon oxide etched compared to silicon nitride.

[0052] The dry etching method of this disclosure can be applied to the process of selectively dry etching only SiO2 from a structure in which SiO2 is adjacent to SiN when forming a semiconductor device on a semiconductor substrate. Examples of such structures include a structure in which a SiN film covers an SiO2 film, or a structure in which an SiO2 film and a SiN film are stacked in sequence. For example, in the manufacturing process of a 3D memory, a laminated film of SiO2 and SiN is formed on a semiconductor substrate, through holes are formed in this laminated film, and an etching gas is supplied to the laminated film from the through holes to apply the dry etching method of this disclosure, thereby selectively etching the SiO2 while leaving the SiN intact. This makes it possible to manufacture a semiconductor device with a structure in which many SiN layers are arranged in parallel with gaps between them.

[0053] The semiconductor device manufacturing method described herein is not applicable only to the semiconductor device manufacturing method described above, but can also be applied to other semiconductor device manufacturing methods that involve etching a silicon oxide film formed on a substrate.

[0054] [Second Embodiment] A second embodiment of the dry etching method of the present disclosure is a method of etching by supplying a processing gas containing an organic amine mixture and a processing gas containing hydrogen fluoride separately to an etching apparatus. That is, in the second embodiment, after the step of supplying a processing gas containing an organic amine mixture to an etching apparatus to silicon oxide, the step of supplying a processing gas containing hydrogen fluoride to the etching apparatus is performed. A vacuuming step may be performed between the above two steps.

[0055] As the above organic amine mixture, an organic amine mixture containing at least two compounds represented by general formula (1) shown in the first embodiment can be used. Since the organic amine mixture containing at least two compounds represented by general formula (1) was described in the first embodiment, a detailed explanation will be omitted here. Among the organic amine mixtures, an organic amine mixture containing a secondary amine and a tertiary amine is preferred, more preferably the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, or ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, or dimethylethylamine, and an organic amine mixture containing trimethylamine and dimethylamine is particularly preferred. By using this organic amine mixture, dry etching of silicon oxide can be performed at a faster rate than in the conventional case.

[0056] In the second embodiment, an organic amine mixture is first introduced into the etching apparatus, and when the silicon oxide is brought into contact with the gaseous organic amine mixture, it is believed that at least two types of organic amine compounds constituting the organic amine mixture are adsorbed onto the surface of the silicon oxide. Subsequently, gaseous hydrogen fluoride is introduced into the etching apparatus, and when the hydrogen fluoride comes into contact with the silicon oxide on which the organic amine compounds constituting the organic amine mixture are adsorbed, it is believed that at least two types of organic amine compounds constituting the adsorbed organic amine mixture are transformed into reaction products such as organic amine salts of hexafluorosilicic acid. Therefore, the reaction product ultimately produced is an organic amine salt of hexafluorosilicic acid, similar to that in the first embodiment, and the above compound sublimes into a gas or decomposes into a gas at the same time as it is produced.

[0057] The first gas introduced into the etching apparatus may consist substantially only of an organic amine mixture, and the second gas introduced may consist only of hydrogen fluoride. Furthermore, the organic amine mixture and hydrogen fluoride may or may not contain an inert gas. As the inert gas, at least one selected from the group consisting of N2, He, Ne, Ar, Kr, and Xe can be used. The proportion of the inert gas in the processing gas is the number of moles of the inert gas divided by the number of moles of hydrogen fluoride, preferably between 0 and 100, more preferably 10 or less, and particularly preferably 5 or less.

[0058] In the step of supplying each processing gas to the silicon oxide, the contact temperature between the organic amine mixture and the silicon oxide is preferably 200°C or lower, more preferably 150°C or lower, and particularly preferably 120°C or lower. Similarly, the contact temperature between hydrogen fluoride and silicon oxide is preferably 200°C or lower, more preferably 150°C or lower, and particularly preferably 120°C or lower. Furthermore, for example, the respective contact temperatures are preferably 20°C or higher, more preferably 50°C or higher, and particularly preferably 80°C or higher. The contact temperatures between the organic amine mixture and silicon oxide and between hydrogen fluoride and silicon oxide may be the same or different.

[0059] The pressure during contact between the organic amine mixture and silicon oxide, and the pressure during contact between hydrogen fluoride and silicon oxide, is preferably 0.1 Pa to 100 kPa, more preferably 0.5 Pa to 50 kPa, and particularly preferably 1 Pa to 10 kPa.

[0060] The form of the silicon oxide to be etched is preferably the same as in the first embodiment, and the dry etching method according to the second embodiment allows for selective etching of the silicon oxide film relative to the silicon nitride film. The silicon oxide / silicon nitride etching selectivity ratio is preferably 2.5 or higher, more preferably 5 or higher, and particularly preferably 10 or higher.

[0061] Furthermore, in the dry etching method of this disclosure, a step of supplying an organic amine mixture may be performed after the step of supplying a processing gas containing hydrogen fluoride gas. Moreover, the step of supplying a processing gas containing hydrogen fluoride gas and the step of supplying an organic amine mixture may be repeated alternately.

[0062] [Etching equipment] In the dry etching method of this embodiment, dry etching can be performed by using an etching apparatus comprising: a processing container having a mounting section on which a substrate to be processed having a silicon oxide film is placed; a hydrogen fluoride gas supply section for supplying a processing gas containing hydrogen fluoride to the processing container; an organic amine mixture supply section for supplying a dry etching gas composition containing an organic amine mixture to the processing container; a vacuum exhaust section for reducing the pressure inside the processing container; and a heating section for heating the mounting section. The etching apparatus may further be equipped with an inert gas supply section for supplying an inert gas to the processing container as needed.

[0063] Figure 1 is a schematic diagram of a reaction apparatus 1, which is an example of an etching apparatus used in the dry etching method according to the embodiment of this disclosure. A stage (placement unit) 3, heated by a heater (heating unit) 8, is installed inside the chamber (processing vessel) 2 that constitutes the reaction apparatus 1. Heaters (not shown) are also installed around the chamber 2 to heat the chamber walls. A processing gas is introduced from a hydrogen fluoride gas supply unit 5a and an organic amine mixture supply unit 5b installed at the top of the chamber 2, and the dry etching gas composition is brought into contact with the sample (substrate to be processed) 4 placed on the stage 3. The gas inside the chamber 2 is discharged via a gas discharge line 6. The chamber 2 is equipped with an inert gas supply unit 5c, and inert gas may be supplied as needed. A vacuum exhaust pump (vacuum exhaust unit) (not shown) is connected to the gas discharge line, and a reduced pressure environment can be created inside the chamber 2. Furthermore, a pressure gauge 7 is installed in the chamber 2. Instead of the hydrogen fluoride gas supply unit 5a and the organic amine mixture supply unit 5b, a hydrogen fluoride gas supply unit of the organic amine mixture may be provided.

[0064] The procedure for removing silicon oxide from sample 4 (a substrate to be treated having a silicon oxide film) in this embodiment will also be briefly described. After heating the temperature of the stage 3 to a predetermined value using the heater 8, a processing gas is introduced into the chamber 2 from the hydrogen fluoride gas supply unit 5a and the organic amine mixture supply unit 5b under conditions based on the first or second embodiment, bringing the sample 4 into contact with the processing gas. At this time, the reaction product is formed by the reaction and simultaneously sublimes, and is removed from the chamber 2 through the gas discharge line 6.

[0065] Furthermore, the reaction apparatus 1 includes a control unit. This control unit consists of, for example, a computer and includes a program, memory, and a CPU. The program incorporates a set of steps to perform a series of operations in the first or second embodiment, and according to the program, it adjusts the temperature of the sample 4, opens and closes the valves of each gas supply unit, adjusts the flow rate of each gas, adjusts the pressure inside the chamber 2, and so on. This program is stored on a computer storage medium, such as a compact disk, hard disk, magneto-optical disk, or memory card, and installed in the control unit.

[0066] [Effects of this embodiment] By using the dry etching method according to the first embodiment or the dry etching method according to the second embodiment described above, it is possible to etch silicon oxide at a higher speed without using plasma, even at low temperatures of 200°C or below.

[0067] In the dry etching method according to the first embodiment or the dry etching method according to the second embodiment, etching can be performed even at low temperatures of 200°C or below without leaving any residue on the silicon oxide surface resulting from the formation of the reaction product layer. Therefore, it is possible to etch the silicon oxide in a single step without performing a PHT treatment to sublimate the reaction product. As a result, silicon oxide can be etched more efficiently than in cycle etching, which involves switching between COR treatment and PHT treatment.

[0068] In the dry etching method according to the first embodiment or the dry etching method according to the second embodiment, silicon oxide can be etched even without heating the substrate to a high temperature exceeding 200°C, and therefore can be suitably applied to substrates made of materials with low heat resistance.

[0069] In the dry etching method according to the first embodiment or the dry etching method according to the second embodiment, silicon oxide can be selectively etched from polycrystalline silicon. In the dry etching method of this embodiment, by using an organic amine mixture, silicon oxide can be etched with a higher silicon oxide / silicon nitride etching selectivity ratio than in conventional methods using ammonia. Furthermore, in the dry etching method of this embodiment, silicon oxide can be etched at a faster speed compared to cases where water or alcohol is added or when a single type of organic amine is used. [Examples]

[0070] Examples of the present disclosure are listed below, along with comparative examples, but the present disclosure is not limited to these examples.

[0071] In Examples 1-4 and Comparative Examples 1-3 described below, dry etching was performed using a reaction apparatus substantially similar to that shown in Figure 1. A silicon wafer with a silicon oxide film formed on it was placed in the reaction apparatus as the substrate to be treated, and the amount of silicon oxide etched was measured.

[0072] [Examples 1-4, Comparative Examples 1-3] First, the substrate to be processed was placed on a stage inside the chamber, the chamber was evacuated, and the stage temperature was set to the temperature for the first treatment as shown in Table 1 below. Then, for the first treatment, a treatment gas such as the organic amine mixture shown in Table 1 was supplied into the chamber at a pressure of 30 Torr and held for 30 seconds. After that, the chamber was evacuated to 1 Torr, and then, for the second treatment, hydrogen fluoride (HF) gas was supplied at a pressure of 30 Torr and held for 30 seconds. After that, the chamber was evacuated to 10 Pa, replaced with an inert gas, and the silicon wafer was removed. The thickness of the silicon oxide film was measured using an optical interferometry film thickness gauge (FILMETRICS F20), and the etching amount was calculated by comparing it with the thickness of the silicon oxide film measured before etching.

[0073] Table 1 below shows the type of processing gas (amine 1 and amine 2) used in the first treatment, the concentration of amine 2 (percentage of amine 2 content relative to the total amount of amine 1 and amine 2 (volume ppm)), the temperature of the silicon wafer during the first treatment, the processing gas (HF) used in the second treatment, the temperature of the silicon wafer during the second treatment, and the amount of etching of the silicon oxide film etched by these treatments. In Examples 1-4, the ratio of Amine 2 to the total amount of Amine 1 and Amine 2 (volume ppm) was varied, as shown in Table 1, but all other conditions remained the same as described above. On the other hand, in Comparative Example 1, as shown in Table 1, only dimethylamine and HF were introduced into the chamber under the conditions described above, as well as in Comparative Example 2, only trimethylamine and HF, and in Comparative Example 3, only ammonia and HF were introduced into the chamber under the conditions described above, and dry etching was performed.

[0074] [Table 1]

[0075] As is clear from the results of the comparison between Examples 1-3 in Table 1 and Comparative Examples 1 and 2, using dimethylamine and trimethylamine as two types of organic amine compounds significantly increases the etching amount compared to using dimethylamine alone (1,000,000 volume ppm = 100 volume%) or trimethylamine alone. Figure 2 is a graph showing the relationship between the concentration of amine 2 (amine 2 / (amine 1 + amine 2) (volume ppm)) and the etching amount when dimethylamine was used as amine 2 in Examples 1 to 3 and Comparative Examples 1 and 2 described above. It can be seen that the etching amount is greatly increased when the concentration of dimethylamine is 100 volume% (1,000,000 volume ppm) and when the concentration of dimethylamine is 0 volume ppm.

[0076] Furthermore, referring to the above examples, it can be estimated that the etching amount is increased when using the two types of organic amine compounds (diethylamine + triethylamine) shown in Example 4, compared to when using the above organic amines individually. This confirmed that while etching proceeds even with a single type of organic amine compound, the etching effect is further improved by using two types of organic amine compounds (secondary amine + tertiary amine).

[0077] Specifically, in Examples 1 to 3, which used a mixed gas of trimethylamine and dimethylamine with dimethylamine content ratios of 38 vol. ppm, 670 vol. ppm, and 9500 vol. ppm, the etching amount of the silicon oxide film was approximately 140 to 180 nm. This represents a significant increase in etching amount compared to Comparative Example 1, which used only dimethylamine gas, and Comparative Example 2, where dimethylamine / (dimethylamine + trimethylamine) = 0 vol. ppm.

[0078] Furthermore, in Example 4, which used triethylamine with a diethylamine content of 180 ppm, the etching amount of the silicon oxide film was 123 nm.

[0079] Furthermore, looking at Figure 2 as a whole, we can see that in the range of dimethylamine content from 10 volume ppm to 10 volume% (100,000 ppm), the etching amount tends to increase compared to dimethylamine alone and trimethylamine alone. In particular, when the dimethylamine content is approximately 100 volume ppm to approximately 5000 volume ppm, the etching amount is approximately 160 nm or more, indicating a significant increase in the etching rate in this range. [Explanation of Symbols]

[0080] 1. Reaction apparatus (etching apparatus) 2 Chambers (processing containers) 3 stages (mounting section) 4. Sample (Substrate to be processed) 5a Hydrogen Fluoride Gas Supply Unit 5b Organic amine mixture supply unit 5c Inert gas supply unit 6. Gas discharge line 7. Pressure gauge 8. Heater (heating section)

Claims

1. A step of reacting silicon oxide with gaseous hydrogen fluoride and a gaseous organic amine compound, a hydrogen fluoride salt of a gaseous organic amine compound, or gaseous hydrogen fluoride, a gaseous organic amine compound, and a hydrogen fluoride salt of a gaseous organic amine compound, The process includes a step of sublimating the reaction product generated by the above reaction without supplying gaseous hydrogen fluoride, gaseous organic amine compounds, or a hydrogen fluoride salt of a gaseous organic amine compound, A dry etching method characterized in that the organic amine compound is an organic amine mixture containing at least two compounds represented by the following general formula (1). 【Chemistry 1】 (In general formula (1), N is a nitrogen atom. R １ is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom or a halogen atom. R ２ , R ３ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom or a halogen atom. However, when the hydrocarbon group has 3 or more carbon atoms, it may have a branched-chain structure or a cyclic structure. The heteroatom of the hydrocarbon group is a nitrogen atom, an oxygen atom, a sulfur atom or a phosphorus atom. Further, when both R １ and R ２ are hydrocarbon groups having 1 or more carbon atoms, R １ and R ２ may be directly bonded to form a cyclic structure. Further, when R １ or R ２ is directly bonded by a double bond to form a cyclic structure, an aromatic ring may be formed without the presence of R ３ . Also, R １ , R ２ and R ３ may be the same hydrocarbon group or different hydrocarbon groups.)

2. The dry etching method according to claim 1, wherein the organic amine mixture comprises at least a secondary amine and a tertiary amine.

3. The dry etching method according to claim 2, wherein the composition ratio of the organic amine mixture is such that the secondary amine comprises 10 volume ppm to 10 volume percent relative to the total amount of the tertiary amine and the secondary amine.

4. The dry etching method according to claim 3, wherein the composition ratio of the organic amine mixture is such that the secondary amine is contained in an amount of 100 volume ppm to 5000 volume ppm relative to the total amount of the tertiary amine and the secondary amine.

5. The dry etching method according to any one of claims 2 to 4, wherein the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, and dimethylethylamine.

6. The dry etching method according to claim 5, wherein the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

7. A dry etching method according to any one of claims 1 to 6, wherein the reaction of a silicon oxide with gaseous hydrogen fluoride and a mixture of gaseous organic amines, a hydrogen fluoride salt of the mixture of gaseous organic amines, or gaseous hydrogen fluoride, a mixture of gaseous organic amines, and a hydrogen fluoride salt of the mixture of gaseous organic amines is carried out without the formation of a plasma state.

8. The dry etching method according to any one of claims 1 to 7, characterized in that the temperature of the silicon oxide during the reaction is 200°C or lower.

9. The above reaction is A dry etching method according to any one of claims 1 to 8, characterized by comprising the step of contacting the silicon oxide with a processing gas containing the hydrogen fluoride and the organic amine mixture, a processing gas containing a hydrogen fluoride salt of the organic amine mixture, or a processing gas containing the hydrogen fluoride, the organic amine mixture, and a hydrogen fluoride salt of the organic amine mixture.

10. The dry etching method according to claim 9, characterized in that the ratio of hydrogen fluoride contained in the processing gas to the organic amine mixture is the value obtained by dividing the total number of moles of organic amine compounds contained in the organic amine mixture by the number of moles of hydrogen fluoride, which is 0.001 or more and 100 or less.

11. The above reaction is A dry etching method according to any one of claims 1 to 8, characterized by comprising the steps of contacting a silicon oxide with a processing gas containing the organic amine mixture and contacting the silicon oxide with a processing gas containing hydrogen fluoride.

12. A dry etching method according to any one of claims 1 to 11, wherein the silicon oxide film is selectively etched on a substrate to be treated in which both the silicon oxide film and the silicon nitride film are exposed.

13. The dry etching method according to claim 12, characterized in that the selectivity ratio of the silicon oxide film to the silicon nitride film is 2.5 or more.

14. A dry etching method according to any one of claims 1 to 11, wherein the silicon oxide film and the polycrystalline silicon film are both exposed on the substrate to be treated, and the silicon oxide film is selectively etched.

15. The dry etching method according to any one of claims 1 to 14, characterized in that heating is performed in the sublimation step.

16. The dry etching method according to claim 15, characterized in that the sublimation step is heated to 200°C or below.

17. The dry etching method according to any one of claims 1 to 16, wherein the organic amine mixture further comprises ammonia.

18. A method for manufacturing a semiconductor device, characterized by including a step of etching a silicon oxide film on a semiconductor substrate having a silicon oxide film by applying the dry etching method described in any one of claims 1 to 17.

19. An organic amine mixture for use in the dry etching method described in claim 1, characterized in that it comprises at least two compounds represented by the following general formula (1). 【Chemistry 2】 (In general formula (1), N is a nitrogen atom. R １ R is a hydrocarbon group having 1 to 10 carbon atoms, which may contain rings, heteroatoms, or halogen atoms. ２ , R ３ This is a hydrocarbon group having a hydrogen atom or 1 to 10 carbon atoms, which may have a ring, heteroatom, or halogen atom. However, if the hydrocarbon group has 3 or more carbon atoms, it may have a branched chain structure or a cyclic structure. The heteroatom of the hydrocarbon group is a nitrogen atom, oxygen atom, sulfur atom, or phosphorus atom. Furthermore, R １ and R ２ If both are hydrocarbon groups having 1 or more carbon atoms, R １ and R ２ They may be directly bonded to form a cyclic structure. Furthermore, R １ or R ２ When R is directly bonded by a double bond to form a cyclic structure, ３ Aromatic rings may be formed even without the presence of R. １ , R ２ and R ３ (These may be the same hydrocarbon group or different hydrocarbon groups.)

20. The organic amine mixture according to claim 19, wherein the organic amine mixture comprises at least a secondary amine and a tertiary amine.

21. The organic amine mixture according to claim 20, wherein the organic amine mixture contains the secondary amine in an amount of 10 ppm to 10% by volume relative to the total amount of the tertiary amine and the secondary amine.

22. The organic amine mixture according to claim 20 or 21, wherein the secondary amine is one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is one of trimethylamine, triethylamine, and dimethylethylamine.

23. The organic amine mixture according to claim 22, wherein the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

24. The organic amine mixture according to any one of claims 19 to 23, wherein the organic amine mixture further comprises ammonia.

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