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

Abstract

The present invention is a dry etching method, characterized in that: it is a dry etching method for silicon oxide in which gaseous hydrogen fluoride and 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 react with silicon oxide, and the above-mentioned organic amine compound is a mixture of at least two organic amines including the compound shown in the following general formula (1). R1-N=R2R3・・・(1) (In general formula (1), N is a nitrogen atom. R1 is a hydrocarbon group with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. R2 and R3 are hydrogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. When the hydrocarbon group has 3 or more carbon atoms, it can form a branched 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, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure. Furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may not be present and an aromatic ring may be formed. Also, R1, R2, and R3 may be the same hydrocarbon group or different hydrocarbon groups.)

Description

[Technical Field]

[0001] This invention 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. [Previous Technology]

[0002] In the manufacturing process of semiconductor devices, there is a step of etching a silicon oxide film that exists on the surface of a semiconductor wafer as a CVD (Chemical Vapor Deposition) oxide film, a thermal oxide film, or a natural oxide film. The etching methods for this silicon oxide film include wet etching using a chemical solution or plasma etching using a reactive gas plasma.

[0003] However, wet etching has the following problems: it can easily cause adverse effects on components that are not being etched due to the chemical solution. Also, plasma etching has the following problems: it can cause electrical damage to the wafer caused by the plasma.

[0004] To address these problems, attempts have been made to perform dry etching without using plasma. For example, a method has been disclosed that, for hydrogen fluoride gas, gaseous water is added to Patent Document 1, gaseous methanol is added to Patent Document 2, gaseous acetic acid is added to Patent Document 3, and gaseous isopropanol is added to perform dry etching of SiO2 without using plasma.

[0005] Furthermore, in order to etch SiO2 at high speed, a method using a mixed gas containing hydrogen fluoride and ammonia has been studied. For example, Patent Document 5 discloses a method for etching in two stages: an AFS layer formation step (Chemical Oxide Removal, COR treatment), in which a mixed gas containing HF and NH3 is supplied to the surface of the silicon oxide film on the substrate, causing the silicon oxide film to chemically react with the mixed gas, thereby transforming the silicon oxide film into ammonium silicate fluoride (AFS), and thus forming the reaction product layer 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 cause it to sublimate or thermally decompose. Previous 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: Japanese Patent Application Publication No. 9-509531; Patent Document 4: Japanese Patent Application Publication No. 2001-503571; Patent Document 5: Japanese Patent Application Publication No. 2007-180418 (Japanese Patent No. 4890025) [Summary of the Invention]

[0007] [The problem the invention aims to solve]

[0008] However, the methods described in Patent Documents 1 to 4 have problems such as insufficient etching rate of SiO2.

[0009] In the method described in Patent Document 5, it is assumed that when only COR treatment is performed, there is a problem that the AFS layer remains on the surface of the silicon oxide film as residue. Furthermore, when a thicker AFS layer is formed during COR treatment, in order to completely remove the AFS layer during PHT treatment, it is necessary to heat to a temperature exceeding 200°C, which also raises concerns about damaging components other than the silicon oxide film.

[0010] Furthermore, since the processing temperature of PHT processing needs to be increased compared to COR processing, there are problems such as needing to heat and cool the chamber each time a step is switched, or needing to divide the chamber for each step, which becomes a factor that reduces productivity.

[0011] The object of the present invention is to provide a dry etching method, a method for manufacturing a semiconductor device using the dry etching method, and a dry etching gas composition, etc., in view of the above-mentioned problems. This dry etching method does not produce residue and can etch silicon oxide at a sufficient speed even at low temperatures below 200°C. [Technical Means for Solving the Problem]

[0012] The inventors conducted intensive research and found that even when an organic amine compound is used as a substitute for NH3 as a base, silicon oxide reacts with HF and the organic amine compound. Since the sublimation temperature of the reaction product is significantly lower than that of ammonium fluoride, the reaction product can be removed at a low temperature. Furthermore, by using at least two organic amine compounds, the etching rate of silicon oxide is further increased, thereby completing the present invention.

[0013] Specifically, the dry etching method of the present invention is characterized in that: it is a dry etching method for silicon oxide in which gaseous hydrogen fluoride and 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 react with silicon oxide, and the above-mentioned organic amine compound is a mixture of at least two kinds of organic amines including the compound shown in the following general formula (1). [Chemistry 1] (In general formula (1), N is a nitrogen atom. R1 is a hydrocarbon group with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. R2 and R3 are hydrogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. When the hydrocarbon group has 3 or more carbon atoms, it can form a branched 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, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure. Furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed. Also, R1, R2, and R3 may be the same hydrocarbon group or different hydrocarbon groups.)

[0014] In the dry etching method of the present invention, the above-mentioned organic amine mixture can be reacted with silicon oxide, and the dry etching of silicon oxide can be performed at a faster speed than in the previous case.

[0015] In the dry etching method of the present invention, it is preferable that the organic amine mixture contains at least a secondary amine and a tertiary amine, and the composition ratio is preferably 10 vol ppm to 10 vol% of the secondary amine relative to the total amount of the tertiary amine and the secondary amine.

[0016] In the dry etching method of the present invention, if the organic amine mixture contains at least a secondary amine and a tertiary amine, and the composition ratio of the secondary amine to the total amount of the tertiary amine and the secondary amine is 10 vol ppm to 10 vol % of the secondary amine, then the dry etching of silicon oxide can be performed at a faster speed.

[0017] In the dry etching method of the present invention, it is preferred 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, more preferably that the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

[0018] In the dry etching method of the present invention, it is preferable that the reaction is carried out without plasma state when the mixture of gaseous hydrogen fluoride and gaseous organic amine, the hydrogen fluoride salt of the mixture of gaseous organic amine, or the hydrogen fluoride salt of the mixture of gaseous hydrogen fluoride, gaseous organic amine and gaseous organic amine reacts with silicon oxide.

[0019] The so-called etching accompanied by plasma state refers to the process in which a halogen gas of about 0.1 to 10 Torr is introduced into the interior of the reaction device, and a high-frequency power is applied to the outer coil or the opposite electrode to generate a low-temperature gas plasma in the reaction device, and the halogen active chemical species formed therein are used to etch silicon oxide and the like.

[0020] In the dry etching method of the present invention, the above-mentioned organic amine mixture can be reacted without plasma, and the above-mentioned gas plasma can be eliminated, and the dry etching of silicon oxide can be performed at a faster rate than in the previous case.

[0021] The method for manufacturing a semiconductor device according to the present invention is characterized by including the following steps: applying the above-mentioned dry etching method to etch the silicon oxide film on a semiconductor substrate having a silicon oxide film.

[0022] The semiconductor device manufacturing method according to the present invention includes a step of etching the silicon oxide film on a semiconductor substrate having a silicon oxide film by applying the above-mentioned dry etching method. Therefore, the etching of the silicon oxide film on the semiconductor substrate can be performed at a faster speed, and the target semiconductor device can be manufactured quickly.

[0023] The dry etching gas composition of the present invention is characterized in that it is a dry etching gas composition comprising a mixture of hydrogen fluoride and an organic amine, wherein the organic amine mixture comprises at least two organic amines containing the compounds shown in the above general formula (1).

[0024] Since the dry etching gas composition of the present invention contains hydrogen fluoride and the above-mentioned organic amine mixture, the dry etching of silicon oxide can be performed at a faster speed than in the previous case.

[0025] The organic amine mixture of the present invention is characterized in that it is an organic amine mixture used in the above-described dry etching method, and contains at least two compounds of the above-described general formula (1). [Effects of the Invention]

[0026] By means of the dry etching method of the present invention, even at low temperatures below 200°C, silicon oxide can be etched at a faster speed than before without producing residue.

Implementation Method

[0027] Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is only one example of the embodiments of the present invention and is not limited to such specific content. Various changes and implementations can be made within the scope of its spirit.

[0028] The dry etching method of the present invention is characterized in that: it is a dry etching method for silicon oxide in which gaseous hydrogen fluoride and 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 react with silicon oxide, and the above-mentioned organic amine compound is a mixture of at least two kinds of organic amines including the compound shown in the following general formula (1). [Chemistry 2] (In general formula (1), N is a nitrogen atom. R1 is a hydrocarbon group with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. R2 and R3 are hydrogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. When the hydrocarbon group has 3 or more carbon atoms, it can form a branched 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, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure. Furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed. Also, R1, R2, and R3 may be the same hydrocarbon group or different hydrocarbon groups.)

[0029] [First Embodiment] In the first embodiment, silicon oxide is dry-etched by supplying gaseous hydrogen fluoride and a mixture of at least two organic amines containing a compound of the above general formula (1) to an etching apparatus and contacting them with silicon oxide. That is, silicon oxide is dry-etched by contacting a processing gas containing the above hydrogen fluoride and the above organic amine mixture, a processing gas containing a hydrogen fluoride salt of the above organic amine mixture, or a processing gas containing the above hydrogen fluoride, the above organic amine mixture, and the above organic amine mixture's hydrogen fluoride salt with silicon oxide.

[0030] If a processing gas containing hydrogen fluoride and at least two organic amines containing compounds of the above general formula (1) is brought into contact with silicon oxide, the silicon oxide reacts chemically with the hydrogen fluoride and the organic amine mixture to form reaction products such as organic amine salts of hexafluorosilicic acid. Silicon oxide is removed by sublimation into gas or thermal decomposition into gas at the same time as the reaction product is generated. Furthermore, in this invention, sublimation refers not only to the case where the solid does not thermally decompose into gas, but also to the case where the solid thermally decomposes into gaseous components.

[0031] In the dry etching method of the present invention, hydrogen fluoride gas and the above-mentioned organic amine mixture can be supplied separately as processing gases and mixed in the etching apparatus. Alternatively, a plurality of organic amine hydrogen fluoride salts obtained by reacting hydrogen fluoride with the organic amine mixture beforehand can be supplied as gases to the etching apparatus. Even when hydrogen fluoride gas and the above-mentioned organic amine mixture are supplied separately and mixed in the etching apparatus, at least a portion of the organic amine hydrogen fluoride salts are generated in the etching apparatus. Therefore, in the etching apparatus, the three components—gaseous hydrogen fluoride, gaseous organic amine mixture, and hydrogen fluoride salts of the above-mentioned organic amine mixture—can coexist and contact silicon oxide, or only the hydrogen fluoride salts of the organic amine mixture can contact silicon oxide, or only gaseous hydrogen fluoride and the organic amine mixture can contact silicon oxide. As a result, regardless of the situation, organic amine salts of hexafluorosilicic acid are generated through the reaction with silicon oxide.

[0032] Regarding the mixing ratio of the hydrogen fluoride and organic amine mixture contained in the treatment gas, 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 is preferably 0.001 to 100, more preferably 0.01 to 10, and even more preferably 0.1 to 5.

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

[0034] In the compound shown in general formula (1), R1 can be exemplified by, for example, methyl, ethyl, propyl, butyl, etc., and some of the hydrogen atoms constituting these organic groups can be replaced by halogens such as fluorine and chlorine. R2 and R3 can be exemplified by, for example, hydrogen atoms, methyl, ethyl, propyl, butyl, etc., and some or all of the hydrogen atoms constituting these organic groups can be replaced by halogens such as fluorine and chlorine. The organic amine shown in the above general formula (1) can 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-mentioned organic amine mixtures include: monomethylamine, dimethylamine, trimethylamine, dimethylethylamine, diethylmethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, ethylpropylamine, di-n-propylamine, monoisopropylamine, ethylisopropylamine, diisopropylamine, monobutylamine, dibutylamine, monotert-butylamine, ditert-butylamine, pyrrolidine, piperidine, piperidine, pyridine, etc. Furthermore, other specific examples include compounds in which some or all of the CH bonds of the above-mentioned compounds become 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 have a pKa of 3.2 or higher than that of HF (hydrogen fluoride) for their conjugate acids, can form salts with hydrogen fluoride, and have a fixed vapor pressure in a temperature range of 20 to 100°C, and therefore do not decompose in this temperature range. They are preferred to be supplied in the form of gas. The organic amine mixture of the present invention can be prepared by mixing at least two of these compounds.

[0037] In particular, in terms of ease of acquisition, the above-mentioned compounds are preferably monomethylamine, dimethylamine, trimethylamine, triethylamine, monoethylamine, monopropylamine, ethylpropylamine, isopropylamine, ethylisopropylamine, 1,1,1-trifluorodimethylamine, 2,2,2-trifluoroethylamine, bis(2,2,2-trifluoroethyl)amine, and preferably prepared by mixing at least two of these compounds to form the organic amine mixture of the present invention.

[0038] Furthermore, regarding the faster etching rate of silicon oxide, the aforementioned organic amine compounds are preferably secondary and tertiary amines. Specific examples of secondary amines include: dimethylamine, diethylamine, ethylisopropylamine, ethylpropylamine, di-n-propylamine, diisopropylamine, dibutylamine, and di-tert-butylamine. Specific examples of tertiary amines include: trimethylamine, dimethylethylamine, diethylmethylamine, and triethylamine.

[0039] The organic amine mixture of the present invention is not particularly limited, and may contain two kinds of organic amines shown in the above general formula (1), or may contain three or more kinds. Examples of specific combinations of organic amines constituting the organic amine mixture include: trimethylamine and dimethylamine, trimethylamine and monomethylamine, trimethylamine and dimethylethylamine, trimethylamine and dimethylamine and monomethylamine and dimethylethylamine, triethylamine and ethylisopropylamine, triethylamine and diethylamine, etc. Furthermore, the organic amine mixture may further contain ammonia.

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

[0041] In the dry etching method of the present invention, 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. More preferably, the secondary amine is dimethylamine, and the tertiary amine is trimethylamine. In this case, the organic amine mixture preferably contains 10 vol ppm to 10 vol% dimethylamine relative to the combined amount of trimethylamine and dimethylamine, and more preferably, it contains 100 vol ppm to 5000 vol ppm dimethylamine relative to the combined amount of trimethylamine and dimethylamine.

[0042] The dry etching gas composition of the present invention is characterized in that it is a dry etching gas composition comprising a mixture of hydrogen fluoride and an organic amine, wherein the organic amine mixture is a mixture of at least two organic amines comprising the compounds shown in the following general formula (1). [Chemical 3] (In general formula (1), N is a nitrogen atom. R1 is a hydrocarbon group with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. R2 and R3 are hydrogen atoms or hydrocarbon groups with 1 to 10 carbon atoms that may have a ring, heteroatom, or halogen atom. When the hydrocarbon group has 3 or more carbon atoms, it can form a branched 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, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure. Furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed. Also, R1, R2, and R3 may be the same hydrocarbon group or different hydrocarbon groups.)

[0043] Furthermore, in the dry etching gas composition of the present invention, the organic amine mixture preferably includes at least a secondary amine and a tertiary amine, 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 even more preferably the secondary amine is dimethylamine and the tertiary amine is trimethylamine. The dry etching gas composition of the present invention may substantially consist only of hydrogen fluoride and the above-mentioned organic amine mixture. Furthermore, the above-mentioned 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 10 vol ppm to 10 vol% of the secondary amine relative to the total amount of the tertiary amine and the secondary amine, and more preferably 100 vol ppm to 5000 vol ppm relative to the total amount of the tertiary amine and the secondary amine.

[0045] The inert gas is preferably selected from at least one of the group consisting of N2, He, Ne, Ar, Kr and Xe, more preferably Ar and N2. The ratio of the inert gas contained in the dry etching gas composition, calculated by dividing the mole number of the inert gas by the mole number of hydrogen fluoride, is preferably 0 to 100, more preferably 10 or less, and even more preferably 5 or less.

[0046] The contact temperature between the dry etching gas composition and silicon oxide (the temperature of silicon oxide) should be above the temperature at which the reaction products of silicon oxide, hydrogen fluoride, and the organic amine mixture sublimate or thermally decompose. Specifically, considering productivity and damage to the substrate being processed, the contact temperature is preferably below 200°C, more preferably below 150°C, and even more preferably below 120°C. Alternatively, for example, the contact temperature is preferably above 20°C, more preferably above 50°C, and even more preferably above 80°C.

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

[0048] Furthermore, during the contact process between the dry etching gas composition and silicon oxide, the temperature and pressure do not need to be constant; they can be changed at fixed intervals. For example, time periods of increasing temperature or decreasing pressure can be set at fixed intervals to promote the sublimation of reaction products.

[0049] Furthermore, as described in Patent Document 5, the following steps can be performed: a COR step, which involves contacting the dry etching gas composition with silicon oxide; and a PHT step, which involves sublimating the reaction product without supplying the dry etching gas composition. In this embodiment, the PHT step may be performed at a temperature of 200°C or below.

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

[0051] In particular, by using the dry etching method of this embodiment on a substrate with both exposed silicon oxide and silicon nitride films, 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, and even more preferably 8 or higher, and most preferably 10 or higher. 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. Furthermore, the etching rate refers to 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 ratio of silicon oxide etched relative to silicon nitride.

[0052] When forming a semiconductor device on a semiconductor substrate, the dry etching method of the present invention can be applied in the step of selectively dry etching only SiO2 from the structure adjacent to SiO2 and SiN. Such structures include structures where a SiN film covers a SiO2 film, or structures where a SiO2 film and a SiN film are sequentially stacked. For example, in the manufacturing process of 3D memory, a stacked film of SiO2 and SiN is formed on a semiconductor substrate, through-holes are formed in the stacked film, and etching gas is supplied to the stacked film through the through-holes. The dry etching method of the present invention is applied to retain SiN and selectively etch SiO2, thereby manufacturing a semiconductor device with a structure in which multiple SiN layers are spaced apart and arranged in parallel.

[0053] The semiconductor device manufacturing method of the present invention can also be applied to other semiconductor device manufacturing methods that involve etching of a silicon oxide film formed on a substrate, rather than only to the semiconductor device manufacturing method described above.

[0054] [Second Embodiment] The second embodiment of the dry etching method of the present invention is a method in which a processing gas containing an organic amine mixture and a processing gas containing hydrogen fluoride are separately supplied to an etching apparatus for etching. That is, in the second embodiment, after the step of supplying the processing gas containing the organic amine mixture to the etching apparatus, the step of supplying the 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-mentioned organic amine mixture, an organic amine mixture comprising at least two compounds of general formula (1) as shown in the first embodiment can be used. The organic amine mixture comprising at least two compounds of general formula (1) has been described in the first embodiment, and therefore a detailed description is omitted here. Preferably, the organic amine mixture comprises a secondary amine and a tertiary amine; more preferably, the secondary amine is any one of dimethylamine, diethylamine, ethylisopropylamine, or ethylpropylamine, and the tertiary amine is any one of trimethylamine, triethylamine, or dimethylethylamine; and most preferably, the organic amine mixture comprises trimethylamine and dimethylamine. By using this organic amine mixture, dry etching of silicon oxide can be performed at a faster speed than previously described.

[0056] In the second embodiment, it is believed that if the organic amine mixture is first introduced into the etching apparatus, and the gaseous organic amine mixture comes into contact with silicon oxide, at least two organic amine compounds constituting the organic amine mixture are adsorbed on the surface of the silicon oxide. It is also believed that if gaseous hydrogen fluoride is subsequently introduced into the etching apparatus, and the hydrogen fluoride comes into contact with the silicon oxide on which the adsorbed organic amine compounds constituting the organic amine mixture are located, the at least two adsorbed organic amine compounds constituting the organic amine mixture are converted into reaction products such as organic amine salts of hexafluorosilicic acid. Therefore, the final reaction product is an organic amine salt of hexafluorosilicic acid, the same as in the first embodiment, which sublimates into a gas or thermally decomposes into a gas upon generation.

[0057] The initial 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 or hydrogen fluoride may or may not contain an inert gas. As an inert gas, at least one gas selected from the group consisting of N2, He, Ne, Ar, Kr, and Xe may be used. The ratio of the inert gas contained in the processing gas, expressed as the mole number of the inert gas divided by the mole number of the hydrogen fluoride, is preferably 0 to 100, more preferably 10 or less, and even more preferably 5 or less.

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

[0059] The pressure when the organic amine mixture comes into contact with silicon oxide and the pressure when hydrogen fluoride comes into contact with silicon oxide are preferably 0.1 Pa to 100 kPa or less, more preferably 0.5 Pa to 50 kPa or less, and even more preferably 1 Pa to 10 kPa or less.

[0060] Preferably, the morphology of the silicon oxide to be etched is the same as in the first embodiment. By means of the dry etching method of the second embodiment, the silicon oxide film can be selectively etched relative to the silicon nitride film. The silicon oxide / silicon nitride etching ratio is preferably 2.5 or higher, more preferably 5 or higher, and even more preferably 10 or higher.

[0061] Furthermore, in the dry etching method of the present invention, after the step of supplying the processing gas containing hydrogen fluoride gas, the step of supplying the organic amine mixture can be performed. Furthermore, the steps of supplying the processing gas containing hydrogen fluoride gas and supplying the organic amine mixture can be performed alternately and repeatedly.

[0062] [Etching Apparatus] In the dry etching method of this embodiment, dry etching can be performed using an etching apparatus, which includes: a processing container having a mounting section for holding a substrate having a silicon oxide film; 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 depressurizing the processing container; and a heating section for heating the mounting section. Furthermore, the etching apparatus may, if necessary, include an inert gas supply section for supplying an inert gas to the processing container.

[0063] FIG1 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 invention. A stage (placement part) 3, heated by a heater (heating part) 8, is provided inside the chamber (processing container) 2 constituting the reaction apparatus 1. A heater (not shown) is also provided around the chamber 2 to heat the chamber walls. Processing gas is introduced from a hydrogen fluoride gas supply part 5a and an organic amine mixture supply part 5b provided at the upper part of the chamber 2, so that the dry etching gas composition comes into contact with the sample (substrate to be processed) 4 placed on the stage 3. The gas inside the chamber 2 is discharged through a gas discharge line 6. The chamber 2 is equipped with an inert gas supply part 5c, which can supply inert gas as needed. Furthermore, a vacuum exhaust pump (vacuum exhaust part) (not shown) is connected to the gas discharge line, which can create a reduced pressure environment inside the chamber 2, and a pressure gauge 7 is provided in the chamber 2. Alternatively, a hydrogen fluoride salt gas supply unit for organic amine mixtures can be provided instead of hydrogen fluoride gas supply unit 5a and organic amine mixture supply unit 5b.

[0064] The operation for removing silicon oxide from sample 4 (the substrate with a silicon oxide film) in this embodiment will also be briefly described. After the stage 3 is heated to a specific temperature by heater 8, processing gas is introduced into chamber 2 from hydrogen fluoride gas supply unit 5a and organic amine mixture supply unit 5b according to the conditions of the first embodiment or the second embodiment, so that sample 4 comes into contact with the processing gas. At this time, the reaction product sublimates while being generated during the reaction and is removed from chamber 2 through gas discharge line 6.

[0065] Furthermore, the reaction apparatus 1 includes a control unit. This control unit includes, for example, a computer, and includes a program, memory, and a CPU (Central Processing Unit). The program is incorporated into the step group in a manner that implements a series of actions in the first or second embodiment. According to 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 in the chamber 2 is adjusted. The program is stored in a computer memory medium, such as a compressed optical disc, hard disk, magneto-optical disc, or memory card, and is installed in the control unit.

[0066] [Effects of this embodiment] By using the dry etching method of the first embodiment or the dry etching method of the second embodiment described above, silicon oxide can be etched at a higher speed without using plasma, even at low temperatures below 200°C.

[0067] In the dry etching method of the first embodiment or the dry etching method of the second embodiment, etching can be performed even at low temperatures below 200°C without leaving residues from the formation of the reaction product layer on the silicon oxide surface. Therefore, silicon oxide can be etched in one step without performing the PHT treatment used to sublimate the reaction products. As a result, silicon oxide can be etched more efficiently than in cyclic etching that involves switching between COR treatment and PHT treatment.

[0068] In the dry etching method of the first embodiment or the dry etching method of the second embodiment, silicon oxide can be etched even when the substrate is not heated to a high temperature of more than 200°C. Therefore, it can be better applied to substrates using materials with low heat resistance.

[0069] In the dry etching method of the first embodiment or the dry etching method of 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, a higher silicon oxide / silicon nitride etching selectivity ratio can be achieved compared to the previous method using ammonia, thus etching silicon oxide. Furthermore, in the dry etching method of this embodiment, compared to the cases where water or alcohol is added, and the cases where only one organic amine is used, silicon oxide can be etched at a higher speed. [Example]

[0070] The following are examples of embodiments and comparative examples of the present invention, but the present invention is not limited to the following embodiments.

[0071] In Examples 1 to 4 and Comparative Examples 1 to 3 below, a reaction apparatus substantially the same as the reaction apparatus shown in FIG1 was used to perform dry etching. Furthermore, a silicon wafer with a silicon oxide film formed thereon was placed in the reaction apparatus as the substrate to be processed, and the amount of silicon oxide etched was measured.

[0072] [Examples 1-4, Comparative Examples 1-3] First, a substrate to be processed was placed on a stage in the chamber. After evacuating the chamber, the temperature of the stage was set to the temperature of the first processing as shown in Table 1 below. Then, as the first processing, the processing gas, such as the organic amine mixture shown in Table 1, was supplied to the chamber at a pressure of 30 Torr and maintained for 30 seconds. Then, the chamber was evacuated to 1 Torr, and as the second processing, hydrogen fluoride (HF) gas was supplied at a pressure of 30 Torr and maintained for 30 seconds. Then, 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 interferometer (F20 manufactured by FILMETRICS Corporation), and compared with the thickness of the silicon oxide film measured before etching, thereby calculating the etching amount.

[0073] Table 1 below shows the types of processing gases (amine 1 and amine 2) such as the organic amine mixture in the first processing, the concentration of amine 2 (the content ratio of amine 2 relative to the total amount of amine 1 and amine 2 (volume ppm)), the temperature of the silicon wafer during the first processing, the processing gas (HF) in the second processing, the temperature of the silicon wafer during the second processing, and the etching amount of the silicon oxide film etched by these processes. Furthermore, in Examples 1 to 4, as shown in Table 1, the content ratio of amine 2 relative to the total amount of amine 1 and amine 2 (volume ppm) was changed, but other conditions were performed under the same conditions as described above. On the other hand, as shown in Table 1, under the above conditions, in Comparative Example 1, only dimethylamine and HF were introduced into the chamber; in Comparative Example 2, only trimethylamine and HF were introduced into the chamber; and in Comparative Example 3, only ammonia and HF were introduced into the chamber for dry etching, instead of introducing the organic amine mixture.

[0074] [Table 1] First processing Second processing Etching depth (nm) Types of organic amine mixed gases Amine 2 concentration [Amine 2 / (Amine 1 + Amine 2)] (volume ppm) Processing temperature (°C) gas Processing temperature (°C) Amine 1 Amine 2 Example 1 Trimethylamine dimethylamine 38 120 HF 120 143 Example 2 Trimethylamine dimethylamine 670 120 HF 120 183 Example 3 Trimethylamine dimethylamine 9500 120 HF 120 143 Example 4 Triethylamine Diethylamine 180 120 HF 120 123 Comparative Example 1 - dimethylamine dimethylamine only 120 HF 120 77 Comparative Example 2 Trimethylamine - Trimethylamine 100 HF 100 99 Comparative Example 3 ammonia - Ammonia only 120 HF 120 38

[0075] As can be seen from the comparison results of Examples 1-3 in Table 1 and Comparative Examples 1 and 2, by using dimethylamine and trimethylamine as two organic amine compounds, the etching amount is significantly increased compared with the cases where only dimethylamine (1,000,000 volume ppm = 100 volume%) and only trimethylamine are used. 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 is used as amine 2 in Examples 1-3 and Comparative Examples 1 and 2. It can be seen that the etching amount is significantly increased compared with the concentration of dimethylamine being 100 volume% (1,000,000 volume ppm) and the concentration of dimethylamine being 0 volume ppm.

[0076] Furthermore, referring to the above embodiments, it is speculated that even when using the two organic amine compounds (diethylamine + triethylamine) shown in Example 4, the etching amount is increased compared to using the organic amine alone. Therefore, it can be confirmed that even with only one organic amine compound, etching occurs, but by using two organic amine compounds (secondary amine + tertiary amine), the etching effect is further improved.

[0077] Specifically, in Examples 1 to 3, in which dimethylamine was used and a mixed gas of trimethylamine and dimethylamine was present in a ratio of 38 ppm, 670 ppm, and 9500 ppm, the etching amount of the silicon oxide film was about 140 to 180 nm, which was significantly increased compared with Comparative Example 1, which used only dimethylamine gas, and Comparative Example 2, in which dimethylamine / (dimethylamine + trimethylamine) = 0 ppm.

[0078] Furthermore, 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, observing the overall picture in Figure 2, it was observed that in the range of dimethylamine content ratio of 10 volume ppm to 10 volume % (100,000 ppm), there is a trend of increasing etching amount compared with dimethylamine alone and trimethylamine alone. It can be seen that, especially when the dimethylamine content ratio is about 100 volume ppm to about 5000 volume ppm, the etching amount is about 160 nm or more. In this range, the etching rate increases significantly. [Simplified Explanation of the Diagram]

[0081] Figure 1 is a schematic diagram of a reaction apparatus as an example of an etching apparatus used in a dry etching method according to an embodiment of the present invention. 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 is used as amine 2 in Examples 1 to 3 and Comparative Examples 1 and 2.

Claims

1. A dry etching method, characterized in that: it is a dry etching method for silicon oxide in which gaseous hydrogen fluoride and gaseous organic amine compounds, hydrogen fluoride salts of gaseous organic amine compounds, or gaseous hydrogen fluoride, gaseous organic amine compounds and hydrogen fluoride salts of gaseous organic amine compounds react with silicon oxide, and the aforementioned organic amine compounds are a mixture of at least two organic amines containing compounds of the following general formula (1), (in general formula (1), N is a nitrogen atom; R1 is a hydrocarbon group having 1 to 10 carbon atoms and may have rings, heteroatoms or halogen atoms; R2, R3 are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms and may have rings, heteroatoms or halogen atoms; wherein, When the hydrocarbon group has 3 or more carbon atoms, it can form a branched structure or a cyclic structure; the heteroatoms of the hydrocarbon group are nitrogen, oxygen, sulfur, or phosphorus atoms; furthermore, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure; furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed; also, R1, R2, and R3 can be the same hydrocarbon group or different hydrocarbon groups.

2. The dry etching method of claim 1, wherein the organic amine mixture contains at least secondary and tertiary amines.

3. The dry etching method of claim 2, wherein the composition ratio of the organic amine mixture relative to the total amount of the tertiary amine and the secondary amine comprises 10 vol ppm to 10 vol% of the secondary amine.

4. The dry etching method of claim 3, wherein the composition ratio of the organic amine mixture, relative to the total amount of the tertiary amine and the secondary amine, includes 100 to 5000 ppm by volume of the secondary amine.

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

7. The dry etching method of any one of claims 1 to 4, wherein the reaction is carried out without plasma when gaseous hydrogen fluoride and a mixture of gaseous organic amines, a hydrogen fluoride salt of a mixture of gaseous organic amines, or gaseous hydrogen fluoride, a mixture of gaseous organic amines and a hydrogen fluoride salt of a mixture of gaseous organic amines react with silicon oxide.

8. The dry etching method of any one of claims 1 to 4, wherein the temperature of the silicon oxide during the above reaction is below 200°C.

9. The dry etching method of claim 1, wherein the reaction comprises the following steps: contacting the silicon oxide with a processing gas containing the above-mentioned hydrogen fluoride and the above-mentioned organic amine mixture, a processing gas containing the above-mentioned organic amine mixture and a hydrogen fluoride salt, or a processing gas containing the above-mentioned hydrogen fluoride, the above-mentioned organic amine mixture and the above-mentioned organic amine mixture and a hydrogen fluoride salt.

10. The dry etching method of claim 9, wherein the ratio of hydrogen fluoride contained in the processing gas to the organic amine mixture is calculated as a value obtained by dividing the total mole number of the organic amine compounds contained in the organic amine mixture by the mole number of hydrogen fluoride, and is 0.001 to 100.

11. The dry etching method of claim 1, wherein the above reaction includes: The steps of contacting the processing gas containing the above-mentioned organic amine mixture with silicon oxide; and the steps of contacting the processing gas containing hydrogen fluoride with the above-mentioned silicon oxide.

12. The dry etching method of any one of claims 1 to 4, wherein the silicon oxide film is selectively etched on the substrate to be treated, where both the silicon oxide film and the silicon nitride film are exposed.

13. The dry etching method of claim 12, wherein the selection ratio of silicon oxide film to silicon nitride film is 2.5 or higher.

14. The dry etching method of any one of claims 1 to 4, wherein the organic amine mixture further comprises ammonia.

15. The dry etching method of claim 9 or 11, wherein the above reaction further includes the step of removing the reaction products generated by the above contact without supplying any of hydrogen fluoride, organic amine compound and hydrogen fluoride salt of organic amine compound.

16. The dry etching method of claim 15, wherein in the step of removing the reaction products generated by the above contact, the reaction products are removed by heating and / or reducing pressure.

17. A method for manufacturing a semiconductor device, characterized by comprising the following steps: etching the silicon oxide film on a semiconductor substrate having a silicon oxide film by applying a dry etching method as described in any one of claims 1 to 16.

18. A dry etching gas composition, characterized in that: it comprises a mixture of hydrogen fluoride and an organic amine, wherein the organic amine mixture is a mixture of at least two organic amines comprising a compound of the following general formula (1), (in general formula (1), N is a nitrogen atom; R1 is a hydrocarbon group having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; R2 and R3 are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; wherein, When the hydrocarbon group has 3 or more carbon atoms, it can form a branched structure or a cyclic structure; the heteroatoms of the hydrocarbon group are nitrogen, oxygen, sulfur, or phosphorus atoms; furthermore, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure; furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed; also, R1, R2, and R3 can be the same hydrocarbon group or different hydrocarbon groups.

19. The dry etching gas composition of claim 18, wherein the organic amine mixture comprises at least a secondary amine and a tertiary amine.

20. The dry etching gas composition of claim 19, wherein the organic amine mixture contains 10 vol ppm to 10 vol% of the secondary amine relative to the combined amount of the tertiary amine and the secondary amine.

21. The dry etching gas composition of claim 19 or 20, 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.

22. The dry etching gas composition of claim 21, wherein the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

23. The dry etching gas composition of any one of claims 18 to 20, wherein the organic amine mixture further comprises ammonia.

24. A dry etching gas composition as claimed in any one of claims 18 to 20, wherein the dry etching gas composition further comprises an inert gas, wherein the inert gas system is selected from at least one of the group consisting of N2, He, Ne, Ar, Kr and Xe.

25. Use of a composition for dry etching, characterized in that: the composition comprises a mixture of gaseous hydrogen fluoride and a gaseous organic amine, wherein the gaseous organic amine mixture is a mixture of at least two of the compounds represented by the following general formula (1), (in general formula (1), N is a nitrogen atom; R1 is a hydrocarbon group having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; R2, R3 are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; wherein, When the hydrocarbon group has 3 or more carbon atoms, it can form a branched structure or a cyclic structure; the heteroatoms of the hydrocarbon group are nitrogen, oxygen, sulfur, or phosphorus atoms; furthermore, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure; furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed; also, R1, R2, and R3 can be the same hydrocarbon group or different hydrocarbon groups.

26. Use of an organic amine mixture in a dry etching method according to any one of claims 1 to 16, characterized in that: the organic amine mixture comprises at least two compounds of the following general formula (1), (in general formula (1), N is a nitrogen atom; R1 is a hydrocarbon group having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; R2 and R3 are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms and may have a ring, heteroatom, or halogen atom; wherein, When the hydrocarbon group has 3 or more carbon atoms, it can form a branched structure or a cyclic structure; the heteroatoms of the hydrocarbon group are nitrogen, oxygen, sulfur, or phosphorus atoms; furthermore, when both R1 and R2 are hydrocarbon groups with 1 or more carbon atoms, R1 and R2 can be directly bonded to form a cyclic structure; furthermore, when R1 or R2 are directly bonded by a double bond to form a cyclic structure, R3 may be absent and an aromatic ring may be formed; also, R1, R2, and R3 can be the same hydrocarbon group or different hydrocarbon groups.

27. As claimed in claim 26, wherein the organic amine mixture comprises at least a secondary amine and a tertiary amine.

28. As claimed in claim 27, wherein the organic amine mixture comprises 10 vol ppm to 10 vol% of the secondary amine relative to the total amount of the tertiary amine and the secondary amine.

29. As claimed in claim 27 or 28, wherein the secondary amine is any one of dimethylamine, diethylamine, ethylisopropylamine, or ethylpropylamine, and the tertiary amine is any one of trimethylamine, triethylamine, or dimethylethylamine.

30. As claimed in claim 29, wherein the secondary amine is dimethylamine and the tertiary amine is trimethylamine.

31. The use of any of claims 26 to 28, wherein the aforementioned organic amine mixture further comprises ammonia.

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