Dry etching method, method of producing semiconductor device, 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] The present 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 manufacturing process of semiconductor devices, there is a process for etching silicon oxide films that exist on the surface of semiconductor wafers as CVD oxide films, thermal oxide films, or natural oxide films. Methods for etching such silicon oxide films include wet etching using chemical solutions and plasma etching using reactive gas plasma.

[0003] However, wet etching has the problem that the chemicals can easily affect materials that are not the target of etching, and plasma etching has the problem that the plasma can cause electrical damage to the wafer.

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

[0005] Also, a method using a mixed gas containing hydrogen fluoride gas and ammonia gas has been considered to etch SiO2 at high speed. For example, Patent Document 5 discloses a two-stage etching method, which includes an AFS layer generation process (Chemical Oxide Removal; COR process) in which a mixed gas containing HF gas and NH3 gas is supplied to the surface of a silicon oxide film on a substrate, the silicon oxide film is chemically reacted with the mixed gas, the silicon oxide film is transformed into ammonium silicofluoride (AFS), and this reaction product layer is generated on the silicon layer of the substrate, and a heating process (Post Heat Treatment; PHT process) in which the AFS layer is heated without supplying the mixed gas to sublimate or pyrolyze it. [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] JP 2007-180418 A (Patent No. 4890025 A) Summary of the Invention [Problem to be solved by the invention]

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

[0008] The method described in Patent Document 5 has a problem that if only the COR process is performed, the AFS layer remains as a residue on the surface of the silicon oxide film. In addition, if a thick AFS layer is formed in the COR process, it is necessary to heat the substrate to a temperature exceeding 200°C in order to completely remove the AFS layer by the PHT process, and there is a concern that this may damage components other than the silicon oxide film.

[0009] Furthermore, since the processing temperature for PHT processing must be higher than that for COR processing, there are problems such as the need to heat and cool the chamber every time the process is switched, and the need to use separate chambers for each process, which are factors that reduce productivity.

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

[0011] As a result of extensive research, the inventors have discovered 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, that the sublimation temperature of the reaction product is significantly lower than that of ammonium silicofluoride, and therefore the reaction product can be removed at a low temperature, and that the etching rate of silicon oxide is further increased by using at least two types of organic amine compounds, thereby completing the present disclosure.

[0012] Specifically, the dry etching method of the present disclosure is a method for dry etching silicon oxide, which comprises 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 characterized in that it is an organic amine mixture containing at least two kinds of compounds represented by the following general formula (1). [ka] (In the general formula (1), N is a nitrogen atom. R 1 R is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. 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. Furthermore, R 1 and R 2 When both are hydrocarbon groups having one or more carbon atoms, R 1 and R 2 may be directly bonded to form a cyclic structure. 1 or R 2 When the double bond directly bonds to the ring structure, R 3 may be absent to form an aromatic ring. 1 , R 2 and R 3 may be the same or different hydrocarbon groups.)

[0013] In the dry etching method of the present disclosure, the above-mentioned 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 method.

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

[0015] In the dry etching method of the present disclosure, when the organic amine mixture contains at least a secondary amine and a tertiary amine and the composition ratio of the secondary amine is 10 volume ppm to 10 volume % with respect to the total amount of the tertiary amine and the secondary amine, dry etching of silicon oxide can be performed at a faster rate.

[0016] In the dry etching method of the present disclosure, it is preferable that the secondary amine is any one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is any 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 the present disclosure, when gaseous hydrogen fluoride and the gaseous organic amine mixture, the hydrogen fluoride salt of the gaseous organic amine mixture, or the gaseous hydrogen fluoride, the gaseous organic amine mixture, and the hydrogen fluoride salt of the gaseous organic amine mixture are reacted with silicon oxide, it is preferable to carry out the reaction without involving a plasma state.

[0018] Etching in a plasma state refers to a process in which a halogen-based gas or the like at about 0.1 to 10 Torr is placed inside a reactor, high-frequency power is applied to the outer coil or opposing electrode to generate low-temperature gas plasma in the reactor, and silicon oxide or the like is etched by the halogen-based activated chemical species produced in the plasma.

[0019] In the dry etching method of the present 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 case without generating the above-mentioned gas plasma.

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

[0021] According to the method for manufacturing a semiconductor device disclosed herein, a step of applying the above-described dry etching method to a semiconductor substrate having a silicon oxide film to etch the silicon oxide film is included. Therefore, the silicon oxide film on the semiconductor substrate can be etched at a high speed, and the desired semiconductor device can be rapidly manufactured.

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

[0023] Because the dry etching gas composition of the present disclosure contains hydrogen fluoride and the above-mentioned organic amine mixture, it is possible to dry etch silicon oxide at a faster rate than is possible with the prior art.

[0024] The organic amine mixture of the present disclosure is an organic amine mixture for use in the above-mentioned dry etching method, and is characterized by containing at least two kinds of compounds represented by the above general formula (1). Effect of the Invention

[0025] The dry etching method of the present disclosure makes it possible to etch silicon oxide at a faster rate than conventional methods, even at low temperatures of 200° C. or less, without generating residues. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of a reaction apparatus that is an example of an etching apparatus used in a dry etching method according to an embodiment of the present disclosure. [Diagram 2]FIG. 2 is a graph showing the relationship between the concentration of amine 2 (amine 2 / (amine 1+amine 2) (ppm by volume)) and the amount of etching when dimethylamine was used as amine 2 in Examples 1 to 3 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present disclosure will be described in detail below, but the following description of the constituent elements is an example of an embodiment of the present disclosure, and the present disclosure is not limited to these specific contents. Various modifications can be made within the scope of the gist of the disclosure.

[0028] The dry etching method of the present disclosure is a method for dry etching silicon oxide, which comprises 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 characterized in that it is an organic amine mixture containing at least two kinds of compounds represented by the following general formula (1). [ka] (In the general formula (1), N is a nitrogen atom. R 1 R is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. 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. Furthermore, R 1 and R 2 When both are hydrocarbon groups having one or more carbon atoms, R 1 and R 2 may be directly bonded to form a cyclic structure. 1 or R 2When the double bond directly bonds to the ring structure, R 3 may be absent to form an aromatic ring. 1 , R 2 and R 3 may be the same or different hydrocarbon groups.)

[0029] [First embodiment] In the first embodiment, an organic amine mixture containing gaseous hydrogen fluoride and at least two of the 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 a hydrogen fluoride salt of the organic amine mixture, or a process gas containing the hydrogen fluoride, the organic amine mixture, and a 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 contacted with a treatment gas containing hydrogen fluoride and an organic amine mixture containing at least two compounds represented by the general formula (1), the silicon oxide undergoes a chemical reaction with the hydrogen fluoride and the organic amine mixture, and changes into a reaction product such as an organic amine salt of hexafluorosilicic acid. The reaction product is sublimated to a gas or pyrolyzed to a gas at the same time as it is generated, and the silicon oxide is removed. In this disclosure, sublimation refers not only to a solid becoming a gas without pyrolysis, but also to a solid becoming a gas component by pyrolysis.

[0031] In the dry etching method of the present disclosure, hydrogen fluoride gas and the organic amine mixture may be supplied separately as processing gases and mixed in the etching apparatus, or hydrogen fluoride salts of multiple organic amines obtained by reacting hydrogen fluoride with the organic amine mixture in advance may be supplied as gases 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 at least in a part of the etching apparatus. Therefore, in the etching apparatus, three components, gaseous hydrogen fluoride, gaseous organic amine mixture, and hydrogen fluoride salts of the organic amine mixture, may coexist and come into contact with silicon oxide, only the hydrogen fluoride salts of the organic amine mixture may come into contact with silicon oxide, or only the gaseous hydrogen fluoride and the organic amine mixture may come into contact with silicon oxide. In either case, the end result is the same: an organic amine salt of hexafluorosilicic acid is produced by the reaction with silicon oxide.

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

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

[0034] In the compound represented by the general formula (1), R 1 Examples of R include a methyl group, an ethyl group, a propyl group, and a butyl group, 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 the organic group include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, etc., 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 above general formula (1) may be a heterocyclic amine having a five-membered ring structure or a six-membered ring structure.

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

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

[0037] In particular, from the viewpoint of easy availability, the above-mentioned 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 prepare the organic amine mixture of the present disclosure by mixing at least two of these compounds.

[0038] In addition, the organic amine compound is preferably a secondary amine or a tertiary amine in terms of a high etching rate of silicon oxide.Specific examples of the secondary amine include dimethylamine, diethylamine, ethylisopropylamine, ethylpropylamine, di-n-propylamine, diisopropylamine, dibutylamine, and di-tertiarybutylamine.Specific examples of the tertiary amine include trimethylamine, dimethylethylamine, diethylmethylamine, and triethylamine.

[0039] The organic amine mixture of the present disclosure is not particularly limited and may contain two types of organic amines represented by the above general formula (1), or may contain three or more types. 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, etc. The organic amine mixture may further contain ammonia.

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

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

[0042] The dry etching gas composition of the present disclosure is a dry etching gas composition comprising hydrogen fluoride and an organic amine mixture, the organic amine mixture comprising at least two kinds of compounds represented by the following general formula (1): [ka] (In the general formula (1), N is a nitrogen atom. R 1 R is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. 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. Furthermore, R 1 and R 2 When both are hydrocarbon groups having one or more carbon atoms, R 1 and R 2 may be directly bonded to form a cyclic structure. 1 or R 2 When the double bond directly bonds to the ring structure, R3 may be absent to form an aromatic ring. 1 , R 2 and R 3 may be the same or different hydrocarbon groups.)

[0043] In addition, in the dry etching gas composition of the present disclosure, the organic amine mixture preferably contains at least a secondary amine and a tertiary amine, and more preferably the secondary amine is any one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is any one of trimethylamine, triethylamine, and dimethylethylamine, and further preferably the secondary amine is dimethylamine and the tertiary amine is trimethylamine. The dry etching gas composition of the present disclosure may be substantially composed of only hydrogen fluoride and the organic amine mixture, and may or may not contain an inert gas.

[0044] The organic amine mixture constituting the dry etching gas composition preferably contains the secondary amine at a ratio of 10 ppm by volume to 10% by volume with respect to the total amount of the tertiary amine and the secondary amine, and more preferably contains the secondary amine at a ratio of 100 ppm by volume to 5000 ppm by volume with respect 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, and more preferably Ar and N2. The ratio of the inert gas contained in the dry etching gas composition, calculated by dividing the number of moles of the inert gas by the number of moles of hydrogen fluoride, is preferably 0 to 100, more preferably 10 or less, and particularly preferably 5 or less.

[0046] The contact temperature between the dry etching gas composition and silicon oxide (temperature of silicon oxide) may be equal to or higher than the temperature at which the reaction product of silicon oxide, hydrogen fluoride, and organic amine mixture sublimes or pyrolyzes. However, in consideration of productivity and damage to the substrate to be treated, 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 during contact between the dry etching gas composition and silicon oxide is not particularly limited, but is preferably from 0.1 Pa to 100 kPa, more preferably from 0.5 Pa to 50 kPa, and particularly preferably from 1 Pa to 10 kPa.

[0048] During the contact between the dry etching gas composition and the silicon oxide, the temperature and pressure do not need to be constant, and may be changed at regular intervals. For example, a period during which the temperature is increased or the pressure is decreased may be set to promote the sublimation of the reaction product.

[0049] Also, as described in Patent Document 5, a COR step in which a 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 less.

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

[0051] In particular, by applying the dry etching method of the present embodiment to a substrate to be processed 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 more, more preferably 5 or more, more preferably 8 or more, and particularly preferably 10 or more. The (silicon oxide / silicon nitride) etching selectivity ratio refers to 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 refers to the value obtained by dividing the change in the thickness of the film 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] When forming a semiconductor device on a semiconductor substrate, the dry etching method of the present disclosure can be applied to a process of selectively dry etching only SiO2 from a structure in which SiO2 is adjacent to SiN. Such structures include a structure in which a SiO2 film is covered with a SiN film, and a structure in which a SiO2 film and a SiN film are laminated in order. For example, in a manufacturing process of a three-dimensional memory, a laminated film of SiO2 and SiN is formed on a semiconductor substrate, a through hole is formed in this laminated film, and an etching gas is supplied from the through hole to the laminated film, and the dry etching method of the present disclosure is applied to selectively etch SiO2 while leaving SiN, thereby manufacturing 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 of the present disclosure is not limited to the semiconductor device manufacturing method described above, but can also be applied to other semiconductor device manufacturing methods involving etching of 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 separately supplying a process gas containing an organic amine mixture and a process gas containing hydrogen fluoride to an etching apparatus. That is, in the second embodiment, a process of supplying a process gas containing an organic amine mixture to silicon oxide to an etching apparatus is performed after a process of supplying a process gas containing hydrogen fluoride to the etching apparatus. A vacuum drawing process may be performed between the above two processes.

[0055] As the organic amine mixture, an organic amine mixture containing at least two kinds of compounds represented by the general formula (1) shown in the first embodiment can be used. The organic amine mixture containing at least two kinds of compounds represented by the general formula (1) has been described in the first embodiment, so a detailed description is omitted here. Among the organic amine mixtures, an organic amine mixture containing a secondary amine and a tertiary amine is preferred, the secondary amine being any one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine being any one of trimethylamine, triethylamine, and 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, it is considered that when the organic amine mixture is first introduced into the etching apparatus and the silicon oxide is brought into contact with the gaseous organic amine mixture, at least two kinds of organic amine compounds constituting the organic amine mixture are adsorbed on the surface of the silicon oxide. After that, when gaseous hydrogen fluoride is introduced into the etching apparatus and hydrogen fluoride comes into contact with the silicon oxide on which the organic amine compounds constituting the organic amine mixture are adsorbed, it is considered that the at least two kinds of organic amine compounds constituting the adsorbed organic amine mixture are changed into reaction products such as organic amine salts of hexafluorosilicic acid. Therefore, the reaction product that is ultimately generated is the organic amine salts of hexafluorosilicic acid similar to the case of the first embodiment, and the above compounds are sublimated into gas or pyrolyzed into gas at the same time as they are generated.

[0057] The first gas introduced into the etching apparatus may consist essentially of the organic amine mixture, and the second gas introduced may consist essentially of hydrogen fluoride. The organic amine mixture or hydrogen fluoride may or may not contain an inert gas. At least one selected from the group consisting of N2, He, Ne, Ar, Kr, and Xe may be used as the inert gas. The ratio of the inert gas contained in the processing gas is the value obtained by dividing the number of moles of the inert gas by the number of moles of hydrogen fluoride, and is preferably 0 to 100, more preferably 10 or less, and particularly preferably 5 or less.

[0058] In the step of supplying each of the treatment gases to the silicon oxide, the contact temperature between the organic amine mixture and the silicon oxide is preferably 200° C. or less, more preferably 150° C. or less, and particularly preferably 120° C. or less. The contact temperature between the hydrogen fluoride and the silicon oxide is preferably 200° C. or less, more preferably 150° C. or less, and particularly preferably 120° C. or less. For example, each of the contact temperatures is preferably 20° C. or more, more preferably 50° C. or more, and particularly preferably 80° C. or more. The contact temperature between the organic amine mixture and the silicon oxide and the contact temperature between the hydrogen fluoride and the 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 are 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 aspect of the silicon oxide to be etched is preferably the same as that of the first embodiment, and the dry etching method according to the second embodiment allows the silicon oxide film to be selectively etched relative to the silicon nitride film. The silicon oxide / silicon nitride etching selectivity is preferably 2.5 or more, more preferably 5 or more, and particularly preferably 10 or more.

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

[0062] [Etching equipment] In the dry etching method of the present embodiment, dry etching can be performed by using an etching apparatus including a processing vessel having a mounting portion for mounting a substrate to be processed having a silicon oxide film thereon, a hydrogen fluoride gas supply portion for supplying a processing gas containing hydrogen fluoride to the processing vessel, an organic amine mixture supply portion for supplying a dry etching gas composition containing an organic amine mixture to the processing vessel, a vacuum exhaust portion for reducing the pressure inside the processing vessel, and a heating portion for heating the mounting portion. The etching apparatus may further include an inert gas supply portion for supplying an inert gas to the processing vessel, if necessary.

[0063] FIG. 1 is a schematic diagram of a reaction apparatus 1 which is an example of an etching apparatus used in a dry etching method according to an embodiment of the present disclosure. A stage (mounting section) 3 heated by a heater (heating section) 8 is installed in a chamber (processing vessel) 2 constituting a reaction apparatus 1. In addition, heaters (not shown) are also installed around the chamber 2, so that the chamber wall can be heated. Processing gas is introduced from a hydrogen fluoride gas supply section 5a and an organic amine mixture supply section 5b installed at the top of the chamber 2, and the dry etching gas composition is brought into contact with a sample (substrate to be processed) 4 installed on the stage 3. The gas in the chamber 2 is exhausted via a gas exhaust line 6. The chamber 2 is equipped with an inert gas supply section 5c, and an inert gas may be supplied as necessary. In addition, a vacuum exhaust pump (vacuum exhaust section) not shown is connected to the gas exhaust line, so that the inside of the chamber 2 can be made into a reduced pressure environment, and a pressure gauge 7 is further installed in the chamber 2. Note that, instead of the hydrogen fluoride gas supply section 5a and the organic amine mixture supply section 5b, a hydrogen fluoride salt gas supply section of the organic amine mixture may be provided.

[0064] The operation for removing silicon oxide from the sample 4 (substrate to be processed having a silicon oxide film) in this embodiment will also be briefly described. After the temperature of the stage 3 is heated to a predetermined value by the heater 8, a process 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, and the sample 4 is brought into contact with the process gas. At this time, a reaction product is generated by the reaction and simultaneously sublimated, and is removed from the chamber 2 through the gas exhaust line 6.

[0065] Furthermore, the reaction apparatus 1 is provided with a control unit. This control unit is, for example, a computer, and is provided with a program, a memory, and a CPU. The program incorporates a group of steps so as to carry out a series of operations in the first or second embodiment, and in accordance with the program, the temperature of the sample 4 is adjusted, the valves of each gas supply unit are opened and closed, the flow rate of each gas is adjusted, and the pressure inside the chamber 2 is adjusted. This program is stored in a computer storage medium, for example, a compact disc, a hard disk, a magneto-optical disc, a memory card, etc., and is 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, it is possible to etch silicon oxide at a high speed without using plasma even at a low temperature of 200° C. or less.

[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 without leaving any residue on the silicon oxide surface resulting from the formation of a reaction product layer even at a low temperature of 200° C. or less, so it is also possible to etch silicon oxide in one step without carrying out a PHT treatment for sublimating the reaction products. As a result, silicon oxide can be etched more efficiently than in cycle etching, which performs etching by switching between a COR treatment and a 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 by using this method even if the substrate is not heated to a high temperature exceeding 200° C., and therefore the method can be suitably applied to a substrate made of a material 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 with respect to polycrystalline silicon. In the dry etching method according to the present embodiment, by using an organic amine mixture, silicon oxide can be etched with a higher silicon oxide / silicon nitride etching selectivity ratio than in the conventional method using ammonia. In addition, in the dry etching method according to the present embodiment, silicon oxide can be etched at a higher speed than in the case where water or alcohol is added or the case where one type of organic amine is used. EXAMPLES

[0070] Examples of the present disclosure will be given below together with comparative examples, but the present disclosure is not limited to the following examples.

[0071] In the following Examples 1 to 4 and Comparative Examples 1 to 3, dry etching was performed using a reaction apparatus substantially similar to the reaction apparatus shown in Fig. 1. In addition, a silicon wafer having a silicon oxide film formed thereon was placed as a substrate to be treated in the reaction apparatus, and the amount of silicon oxide etched was measured.

[0072] [Examples 1 to 4, Comparative Examples 1 to 3] First, the substrate to be treated was placed on the stage in the chamber, the chamber was evacuated, and the stage temperature was set to the temperature for the first treatment shown in Table 1 below. Then, as the first treatment, a treatment gas such as an organic amine mixture shown in Table 1 was supplied to the chamber to a pressure of 30 Torr and held for 30 seconds. Then, the chamber was evacuated to 1 Torr, and then, as the second treatment, hydrogen fluoride (HF) gas was supplied to a pressure of 30 Torr and held for 30 seconds. Then, the chamber was evacuated to 10 Pa and replaced with an inert gas, after which the silicon wafer was taken out, and the thickness of the silicon oxide film was measured with an optical interference film thickness meter (F20 manufactured by FILMETRICS Co., Ltd.), 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 types of process gases (amine 1 and amine 2) such as the organic amine mixture in the first process, the amine 2 concentration (the content ratio of amine 2 to the total amount of amine 1 and amine 2 (ppm by volume)), the temperature of the silicon wafer in the first process, the process gas (HF) in the second process, the temperature of the silicon wafer in the second process, and the amount of silicon oxide film etched by these processes. In Examples 1 to 4, as shown in Table 1, the content ratio (ppm by volume) of amine 2 relative to the total amount of amine 1 and amine 2 was changed, but the other conditions were the same as those described above. On the other hand, in Comparative Example 1, as shown in Table 1, instead of the organic amine mixture, only dimethylamine and HF, in Comparative Example 2, only trimethylamine and HF, and in Comparative Example 3, only ammonia and HF were introduced into the chamber under the above-mentioned conditions to perform dry etching.

[0074] [Table 1]

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

[0076] In addition, referring to the above examples, it is estimated that the etching amount is increased when two types of organic amine compounds (diethylamine + triethylamine) shown in Example 4 are used, as compared with the case where the organic amine is used alone. This confirmed that although etching proceeds even with the use of one 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 in which mixed gases of trimethylamine and dimethylamine with dimethylamine contents of 38 ppm by volume, 670 ppm by volume, and 9,500 ppm by volume were used, the etching amount of the silicon oxide film was approximately 140 to 180 nm, which was a large increase compared to Comparative Example 1 in which only dimethylamine gas was used and Comparative Example 2 in which dimethylamine / (dimethylamine+trimethylamine)=0 ppm by volume.

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

[0079] Furthermore, looking at FIG. 2 as a whole, there is a tendency for the amount of etching to increase when the dimethylamine content is in the range of 10 ppm by volume to 10% by volume (100,000 ppm) compared to dimethylamine alone and trimethylamine alone. In particular, when the dimethylamine content is in the range of approximately 100 ppm by volume to approximately 5000 ppm by volume, the amount of etching is approximately 160 nm or more, and it is clear that the etching rate increases significantly in this range. [Explanation of symbols]

[0080] 1. Reactor (etching equipment) 2. Chamber (processing vessel) 3 Stage (Placement) 4 Sample (substrate to be treated) 5a Hydrogen fluoride gas supply unit 5b Organic amine mixture supply section 5c Inert gas supply section 6 Gas exhaust line 7. Pressure Gauge 8 Heater (heating part)

Claims

1. a step of reacting a 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; sublimating a reaction product produced by the reaction without supplying gaseous hydrogen fluoride and a gaseous organic amine compound, a hydrogen fluoride salt of a gaseous organic amine compound, or a gaseous hydrogen fluoride, a gaseous organic amine compound, and a hydrogen fluoride salt of a gaseous organic amine compound; 2. A dry etching method, wherein the organic amine compound is an organic amine mixture containing at least two kinds of compounds represented by the following general formula (1): 【Chemistry 1】 (In general formula (1), N is a nitrogen atom. R １ R is a hydrocarbon group having 1 to 10 carbon atoms, which may have a ring, a heteroatom, or a halogen atom. 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. Furthermore, R １ and R ２ When both are hydrocarbon groups having one or more carbon atoms, R １ and R ２ may be directly bonded to form a cyclic structure. １ Or R ２ is directly bonded to form a cyclic structure, R ３ may be absent to form an aromatic ring. １ , R ２ and R ３ may be the same or different hydrocarbon groups.)

2. 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. 3. The dry etching method according to claim 2, wherein the organic amine mixture contains the secondary amine in an amount of 10 ppm by volume to 10% by volume with respect to the total amount of the tertiary amine and the secondary amine.

4. 4. The dry etching method according to claim 3, wherein the organic amine mixture contains the secondary amine in an amount of 100 ppm by volume to 5000 ppm by volume with respect 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 any one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is any one of trimethylamine, triethylamine, and dimethylethylamine.

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

7. 7. The dry etching method according to claim 1, wherein the gaseous hydrogen fluoride and the gaseous organic amine mixture, the hydrogen fluoride salt of the gaseous organic amine mixture, or the gaseous hydrogen fluoride, the gaseous organic amine mixture, and the hydrogen fluoride salt of the gaseous organic amine mixture are reacted with silicon oxide without being accompanied by a plasma state.

8. 8. The dry etching method according to claim 1, wherein the temperature of the silicon oxide during the reaction is 200° C. or lower.

9. The reaction is 9. The dry etching method according to claim 1, further comprising a step of contacting the silicon oxide with a process gas containing the hydrogen fluoride and the organic amine mixture, a process gas containing a hydrogen fluoride salt of the organic amine mixture, or a process gas containing the hydrogen fluoride, the organic amine mixture, and a hydrogen fluoride salt of the organic amine mixture.

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

11. The reaction is 9. The dry etching method according to claim 1, further comprising the steps of: bringing a process gas containing the organic amine mixture into contact with a silicon oxide; and bringing a process gas containing hydrogen fluoride into contact with the silicon oxide.

12. 12. The dry etching method according to claim 1, wherein the silicon oxide film is selectively etched on a substrate to be processed on which both a silicon oxide film and a silicon nitride film are exposed.

13. 13. The dry etching method according to claim 12, wherein a selectivity of the silicon oxide film to the silicon nitride film is 2.5 or more.

14. 12. The dry etching method according to claim 1, wherein the silicon oxide film is selectively etched on a substrate to be processed on which both a silicon oxide film and a polycrystalline silicon film are exposed.

15. 15. The dry etching method according to claim 1, wherein heating is performed in the sublimation step.

16. 16. The dry etching method according to claim 15, wherein the step of sublimating comprises heating to 200[deg.] C. or less.

17. 17. The dry etching method according to claim 1, wherein the organic amine mixture further contains ammonia.

18. A method for manufacturing a semiconductor device, comprising the step of applying the dry etching method according to any one of claims 1 to 17 to a semiconductor substrate having a silicon oxide film, thereby etching the silicon oxide film.

19. An organic amine mixture for use in the dry etching method according to any one of claims 1 to 17, comprising 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 have a ring, a heteroatom, or a halogen atom. 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. Furthermore, R １ and R ２ When both are hydrocarbon groups having one or more carbon atoms, R １ and R ２ may be directly bonded to form a cyclic structure. １ Or R ２ is directly bonded to form a cyclic structure, R ３ may be absent to form an aromatic ring. １ , R ２ and R ３ may be the same or different hydrocarbon groups.)

20. 20. The organic amine mixture of 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 by volume to 10% by volume based on 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 any one of dimethylamine, diethylamine, ethylisopropylamine, and ethylpropylamine, and the tertiary amine is any one of trimethylamine, triethylamine, and dimethylethylamine.

23. 23. The organic amine mixture of 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, further comprising ammonia.

Images