Etching composition, etching method, and method for producing semiconductor device

Abstract

Provided are an etching composition suitable for manufacturing BSPDN, an etching method using the etching composition, a method for manufacturing a semiconductor device, and a method for manufacturing a transistor having a BSPDN structure.　This etching composition contains an alkaline compound (A) and an azo compound (B1), and selectively etches silicon with respect to silicon germanium.

Description

Etching Composition, Etching Method, and Method of Manufacturing Semiconductor Device

[0001] The present invention relates to an etching composition, an etching method, and a method of manufacturing a semiconductor device.

[0002] In semiconductor integrated circuits, the integration rate of transistors is advancing at a rate such that it doubles in two years (Moore's law), and circuit miniaturization, which is a fundamental technology for improving the integration rate, is also being advanced by various methods. In recent years, not only reducing the size of conventional planar transistors, but also further miniaturization and integration for improving performance by changing the structure from planar to three-dimensional, such as Fin-type transistors (Fin-type FETs) and gate-all-around transistors (GAA-type FETs), have been studied. As a transistor structure that can be expected to be further miniaturized, a vertical transistor (VFET) has been studied, in which the structure is changed from a conventional planar transistor to a vertical one, enabling further miniaturization and performance improvement.

[0003] In a GAA-type FET, a nano-sheet or nano-wire-shaped channel is covered with a gate electrode, and the performance of transistors per unit area is improved by increasing the contact area between the channel and the gate electrode.

[0004] In a VFET, a structure in which nano-sheet or nano-wire-shaped channels are stacked in the vertical direction, and the area of the standard cell layout is smaller than that of a planar transistor (HFET), thereby improving the performance of transistors per unit area.

[0005] To form GAA-type FETs and VFETs, an etching composition that dissolves silicon is required in the etching process. As an etching composition that dissolves silicon, for example, Patent Document 1 and Patent Document 2 disclose an etching composition containing an alkaline compound.

[0006] Japanese Patent Application Laid-Open No. 2017-108122 Japanese Patent Application Laid-Open No. 2021-136429

[0007] In recent years, a structure called a backside power delivery network (hereinafter referred to as "BSPDN") has been considered in order to achieve further miniaturization. In conventional transistors, the wiring network for supplying power was formed on top of the transistor. However, as the level of integration increased, these wiring networks hindered the improvement of transistor integration density per unit area. Therefore, the BSPDN is a structure that aims to improve integration density by supplying power from the back side.

[0008] The manufacturing process for BSPDN includes a step of bonding a silicon wafer with a device surface formed on it to another silicon wafer, and then etching and thinning the silicon layer on the wafer opposite to the side with the device surface. In this process, a SiGe layer is provided in advance as a stop layer to halt the etching. Therefore, in the manufacturing of BSPDN, an etching composition that selectively dissolves Si in SiGe is required. Furthermore, in order to improve the productivity of the etching process after the thinning of the silicon layer, an etching composition with excellent flatness of the silicon surface after etching is required.

[0009] This invention has been made in view of the above problems, and an object of this invention is to provide an etching composition suitable for the manufacture of BSPDN. Another object of this invention is to provide an etching method using the etching composition, a method for manufacturing a semiconductor device, and a method for manufacturing a transistor having a BSPDN structure. Furthermore, an object of this invention is to provide a composition that can be used for etching and the like, which contains an azo compound (B2) in which the carbon atom adjacent to the nitrogen atom forming the azo bond is a tertiary carbon.

[0010] As a result of diligent research, the inventors have found that etching compositions containing an alkaline compound (A) and a radical generator (B), and etching compositions containing an alkaline compound (A) and a radical (B'), exhibit excellent selective solubility of silicon in silicon germanium. They have also found that etching compositions containing an alkaline compound (A) and a radical generator (B) or a radical (B') exhibit excellent flatness of the silicon surface after etching. The inventors have also found that etching compositions containing an azo compound (B1) as the radical generator (B) exhibit excellent selective solubility of silicon in silicon germanium. These findings have led to the completion of the present invention.

[0011] In other words, the gist of the present invention is as follows: [1] An etching composition comprising an alkaline compound (A) and an azo compound (B1) that selectively etches silicon with respect to silicon germanium. [2] The etching composition according to [1], wherein the alkaline compound (A) comprises at least one compound selected from the group consisting of quaternary ammonium hydroxide compounds, amine compounds, and metal hydroxides. [3] The etching composition according to [1] or [2], wherein the alkaline compound (A) comprises a quaternary ammonium hydroxide compound. [4] The etching composition according to claim 1, wherein the azo compound (B1) is represented in the form of the following general formula (1). (In the above general formula (1), R １ R ２ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ２ R １ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ４ R ５ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ５ R４ It may combine to form a ring, and is a functional group selected from hydrocarbon groups which may have substituents, cyano groups, carboxyl groups, ester groups, amide groups and amidine groups, R ３ and R ６ are each independently a functional group selected from hydrocarbon groups which may have substituents, cyano groups, carboxyl groups, ester groups, amide groups and amidine groups. ) [5] The etching composition according to [4], wherein the azo compound (B1) is an azo initiator. [6] The etching composition according to [5], wherein the azo initiator is represented by the following general formula (2) or (3). (In the above general formula (2), R １ , R ４ are each independently a functional group selected from hydrocarbon groups which may have substituents, cyano groups, carboxyl groups, ester groups, amide groups and amidine groups. ) (In the above general formula (3), R １ , R ３ , R ４ , R ６Each of these is independently a functional group selected from a hydrocarbon group which may have substituents, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group.) [7] The etching composition according to any one of [1] to [6], wherein the content of the alkaline compound (A) in 100% by mass of the etching composition is 0.01% by mass to 40% by mass. [8] The etching composition according to any one of [1] to [7], wherein the content of the azo compound (B1) in 100% by mass of the etching composition is 0.01% by mass to 20% by mass. [9] The etching composition according to any one of [1] to [8], wherein the ratio of the content (by mass) of the azo compound (B1) to the content (by mass) of the alkaline compound (A) is 0.2 to 5.

[10] The etching composition according to any one of [1] to [9], further comprising water.

[11] The etching composition according to any one of [1] to

[10] , wherein the pH of the etching composition is 8.0 to 14.

[12] The etching composition according to any one of [1] to

[11] , wherein the etching composition has a temperature of 20°C to 95°C.

[13] A composition comprising a quaternary ammonium compound (A2) and an azo compound (B2), wherein the azo compound (B2) has a tertiary carbon atom adjacent to the nitrogen atom forming the azo bond, and has a pH of 10 or higher.

[14] An etching method for selectively etching a silicon surface from a structure including a silicon surface and a silicon germanium surface using the etching composition according to any one of [1] to

[12] .

[15] A method for manufacturing a semiconductor device, comprising the step of etching a silicon-containing structure using the etching composition according to any one of [1] to

[12] .

[16] A method for manufacturing a transistor, comprising the step of etching a silicon-containing structure using the etching composition according to any one of [1] to

[12] .

[17] A method for manufacturing a transistor having a BSPDN structure, comprising the step of etching a silicon-containing structure using the etching composition according to any one of [1] to

[12] .

[18] An etching method for selectively etching silicon with respect to silicon germanium using a composition comprising an alkaline compound (A) and an azo compound (B1).

[19] Use of a composition comprising an alkaline compound (A) and an azo compound (B1) for etching, which selectively etches silicon with respect to silicon germanium.

[0012] According to the present invention, it is possible to provide an etching composition suitable for the manufacture of BSPDNs, and an etching method using the etching composition, a method for manufacturing a semiconductor device, and a method for manufacturing a transistor having a BSPDN structure.

[0013] The present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be implemented with various modifications within the scope of its gist. In this specification, when the expression "~" is used, it is used to include the numerical values ​​or physical properties before and after it.

[0014] [Etching composition according to the first embodiment] The etching composition according to the first embodiment of the present invention is characterized by comprising an alkaline compound (A) (hereinafter sometimes referred to as "component (A)") and a radical generator (B) (hereinafter sometimes referred to as "component (B)"). Preferably, the etching composition of the present invention further comprises water (hereinafter sometimes referred to as "component (C)").

[0015] (Component (A)) Component (A) is an alkaline compound. The etching composition of the present invention contains alkaline compound (A), which provides excellent silicon solubility.

[0016] Examples of component (A) include organic alkali compounds such as quaternary ammonium hydroxide compounds like tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and ethyltrimethylammonium hydroxide; amine compounds such as ethanolamine, trimethyleneamine, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, diethylenetriaminepentakis(methylphosphonic acid), ethylenediamine-N,N'-bis[2-(2-hydroxyphenyl)acetic acid], N,N'-bis(3-aminopropane)ethylenediamine, N-methyl-1,3-diaminopropane, 2-aminoethanol, N-methyldiethanolamine, and 2-amino-2-methyl-1-propanol; and inorganic alkali compounds such as metal hydroxides like sodium hydroxide, potassium hydroxide, and calcium hydroxide. These components (A) may be used individually or in combination of two or more. Among these components (A), quaternary ammonium hydroxide compounds, amine compounds, and metal hydroxides are preferred due to their low sodium content, which is likely to affect transistor performance. Quaternary ammonium hydroxide compounds are more preferred, and tetramethylammonium hydroxide, tetraethylammonium hydroxide, and ethyltrimethylammonium hydroxide are even more preferred.

[0017] The content (mass%) of component (A) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, particularly preferably 3% by mass or more, and most preferably 5% by mass or more, based on 100% by mass of the etching composition, due to its excellent solubility in silicon. The content (mass%) of component (A) is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the etching composition, due to its excellent solubility in water.

[0018] (Component (B)) Component (B) in the present invention refers to a substance (excluding hydrogen peroxide) that generates radicals in the etching composition of the present invention. The inclusion of radical generator (B) in the etching composition of the present invention promotes the protection of silicon germanium. Hydrogen peroxide also exhibits strong properties as an oxidizing and reducing agent and can cause a different reaction with the etching substrate than radical generator (B) in the present invention; therefore, hydrogen peroxide is not included in radical generator (B) in the present invention.

[0019] Component (B) is not particularly limited as long as it is a radical generator, but it is preferable to include at least one compound selected from the group consisting of azo compounds, dihalogens, peroxides, benzoin ethers, and acylphosphine oxides. These components (B) may be used individually or in combination of two or more. Among these components (B), a radical generator in which the radicals generated by component (B) become organic radicals is preferred due to its high protective power against silicon germanium, and it is more preferable to use an azo compound (B1) (hereinafter sometimes referred to as "component (B1)").

[0020] (Azo compound (B1)) The azo compound (B1) used in the present invention is not particularly limited, but it is preferable that the azo compound (B1) generates organic radicals upon decomposition, and more preferably an azo compound represented by the following general formula (1).

[0021] (In the above general formula (1), R １ R ２ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ２ R １ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ４ R ５A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ５ R ４ A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R ３ and R ６ Each of these is an independently selected functional group from a hydrocarbon group (which may have substituents), a cyano group, a carboxyl group, an ester group, an amide group, and an amidine group.

[0022] Because silicon germanium has high protective power, in the above general formula (1), R １ The alkyl group is preferably a C1-C6 alkyl group, and is a methyl group, an ethyl group, R ２ A cyclohexyl group or cyclopentyl group bonded to it is more preferable, and a methyl group or ethyl group is particularly preferred. １ R may have substituents, and if so, the substituents are preferably functional groups selected from cyano, carboxyl, ester, amide, and amidine groups. ２ R １ For the same reasons as described above, alkyl groups having 1 to 6 carbon atoms are preferred, including methyl groups, ethyl groups, propyl groups, and R １ A cyclohexyl group or cyclopentyl group bonded to it is more preferable. ２ R may have substituents, and if so, the substituents are preferably functional groups selected from cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, and are particularly preferably nitrogen-containing functional groups such as cyano groups, amide groups, and amidine groups. ３ R １For the same reasons as described above, it is preferable that the functional group is selected from C1-C6 alkyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may have substituents; more preferably, it is selected from methyl groups, ethyl groups, propyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups; and particularly preferably, it is a methyl group or a cyano group. ３ R may have substituents, and if so, the substituents are preferably functional groups selected from cyano, carboxyl, ester, amide, and amidine groups. ４ R １ For the same reasons as described above, alkyl groups having 1 to 6 carbon atoms are preferred, including methyl groups, ethyl groups, and R ５ A cyclohexyl group or cyclopentyl group bonded to it is more preferable, and a methyl group or ethyl group is particularly preferred. ４ R may have substituents, and if so, the substituents are preferably functional groups selected from cyano, carboxyl, ester, amide, and amidine groups. ５ R １ For the same reasons as described above, alkyl groups having 1 to 6 carbon atoms are preferred, including methyl groups, ethyl groups, propyl groups, and R ４ A cyclohexyl group or cyclopentyl group bonded to it is more preferable. ５ R may have substituents, and if it does, it is preferably a functional group selected from cyano group, carboxyl group, ester group, amide group, and amidine group, and is particularly preferably a nitrogen-containing functional group such as a cyano group, amide group, or amidine group. ６ R １ For the same reasons as described above, it is preferable that the functional group is selected from C1-C6 alkyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may have substituents; more preferably, it is selected from methyl groups, ethyl groups, propyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups; and particularly preferably, it is a methyl group or a cyano group. ６R may have substituents, and if so, the substituents are preferably functional groups selected from cyano, carboxyl, ester, amide, and amidine groups. １ ~R ６ Although they are independent of each other, R is used because it facilitates the synthesis of azo compounds. １ and R 4 , R ２ and R ５ , R ３ and R ６ It is preferable that these are the same. Here, the azo compound (B1) described above, which becomes an organic radical as a radical generator (B), is a compound having an azo group (R-N=N-R') that decomposes upon heat or light to generate a carbon radical, and is known as an azo initiator.

[0023] In the present invention, as the azo compound (B1) used, an azo compound represented by the following general formula (2) or (3), i.e., an azo initiator, is also preferred.

[0024] (In the above general formula (2), R １ , R ４ These are functional groups selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, each of which may independently have substituents. (In the above general formula (3), R １ , R ３ , R ４ , R ６ Each of these is independently a functional group selected from a hydrocarbon group (which may have substituents), a cyano group, a carboxyl group, an ester group, an amide group, and an amidine group.

[0025] By using the azo compound represented by formula (2) or (3) above as component (B1) of the etching composition of the present invention, the protective power of silicon germanium is further enhanced, and an etching composition that can selectively etch the silicon surface is more easily obtained.

[0026] Examples of azo compounds represented by the above general formula (1) include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (V-65), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), 1,1'-azobis(cyclohexane-1-carbonitride) (V-40), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086), 2,2' Examples include -azobis(N-butyl-2-methylpropionamide) (VAm-110), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine], 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride.

[0027] The etching composition of the present invention preferably contains water (component (C)) as described later. Therefore, the radical generator (B) is preferably water-soluble. Examples of water-soluble azo initiators include 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine], 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride.

[0028] Here, a water-soluble radical initiator means one in which, according to JIS K8001:2017 General Rules for Reagent Testing Methods, 1 g of radical initiator powder is placed in water and shaken vigorously for 30 seconds every 5 minutes at 20°C ± 5°C, and the volume of water required to dissolve it within 30 minutes is less than 1000 mL (classified as "difficult to dissolve" to "very easily soluble" in the terms used to describe the degree of solubility in the aforementioned JIS standard). It is more preferable that the volume of water is less than 100 mL, even more preferable that it is less than 30 mL, and particularly preferable that it is less than 10 mL.

[0029] (Dihalogens) In the present invention, any halogen can be used as a dihalogen, as long as it is a substance having a halogen-halogen bond, such as a compound or halogen molecule having a halogen-halogen bond.

[0030] (Peroxide) The peroxides used in the present invention are not particularly limited, except for hydrogen peroxide, but examples include organic peroxides such as percarboxylic acids such as metachloroperbenzoic acid, diacyl peroxides such as t-butylperoxybenzoate, benzoyl peroxide, lauroyl peroxide, bis(3,5,5-trimethylhexanoyl) peroxide, diacetyl peroxide, and dipropionyl peroxide, peroxydicarbonates such as diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di(2-ethoxyethyl)peroxydicarbonate, peroxyesters such as t-butylperoxybenzoate and t-butyl peroxypivalate, and hydroperoxides such as t-butyl hydroperoxide, t-amyl hydroperoxide, p-diisopropylbenzene hydroperoxide, cumene hydroperoxide, pinan hydroperoxide, p-menthane hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide.

[0031] (Benzoin ethers) The benzoin ethers used in the present invention are not particularly limited, but examples include isobutyl benzoin ether and isopropyl benzoin ether.

[0032] (Acylphosphine Oxides) The acylphosphine oxides used in the present invention are not particularly limited, but examples include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0033] The radical generators (B) described above include those classified as thermal radical generators, photoradical generators, and redox-type radical generators. Among these, thermal radical generators and photoradical generators are preferred because they exhibit excellent selective solubility of silicon in silicon germanium.

[0034] In the present invention, as described above, it is more preferable to use an azo compound (B1) as a radical generator in which the radicals generated by component (B) become organic radicals. Therefore, an etching composition comprising an alkaline compound (A) and an azo compound (B1) is preferred. Furthermore, since the etching composition exhibits excellent selective solubility of silicon in silicon germanium, an etching composition comprising an alkaline compound (A) and an azo compound (B1) that selectively etches silicon in silicon germanium is more preferred.

[0035] The content of component (B), such as component (B1), is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, and particularly preferably 5% by mass, based on 100% by mass of the etching composition, as it is excellent in protecting silicon germanium. The content of component (B), such as component (B1), is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the etching composition, as it is excellent in dissolving silicon.

[0036] (Component (C)) The etching composition of the present invention preferably contains water (component (C)) in addition to components (A) and (B).

[0037] The content of component (C) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the etching composition, because it facilitates the manufacture of the etching composition and provides excellent solubility for components (A) and (B). The content of component (C) is preferably 99.5% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less, based on 100% by mass of the etching composition, because it provides excellent solubility for silicon.

[0038] (Other Components) The etching composition of the present invention may contain other components in addition to components (A), (B), and (C), as long as they do not impair the effects of the present invention. Examples of other components include chelating agents, water-miscible solvents, surfactants, and the like.

[0039] <Chelating agent> The etching composition of the present invention contains a chelating agent, which provides a protective effect on silicon germanium.

[0040] Examples of chelating agents include amino acids and organic acids. These chelating agents may be used individually or in combination of two or more. Among these chelating agents, amino acids and organic acids are preferred, and amino acids are more preferred, due to their excellent chelating effect.

[0041] Examples of amino acids include glycine, arginine, histidine, and (2-dihydroxyethyl)glycine. These amino acids may be used individually or in combination of two or more. Among these amino acids, (2-dihydroxyethyl)glycine is more preferred due to its excellent chelating effect.

[0042] Examples of organic acids include oxalic acid, citric acid, tartaric acid, malic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid. These organic acids may be used individually or in combination of two or more. Among these organic acids, citric acid and 2-phosphonobutane-1,2,4-tricarboxylic acid are more preferred due to their excellent chelating effect.

[0043] When the etching composition of the present invention contains a chelating agent, the chelating agent content is preferably 0.0010% by mass or more, more preferably 0.0050% by mass or more, and even more preferably 0.010% by mass or more, based on 100% by mass of the etching composition, due to its excellent chelating effect. When the etching composition of the present invention contains a chelating agent, the chelating agent content is preferably 25% by mass or less, more preferably 10% by mass or less, and even more preferably 6.0% by mass or less, based on 100% by mass of the etching composition, due to its excellent solubility in water.

[0044] <Water-miscible solvent> The etching composition of the present invention contains a water-miscible solvent, which exhibits the effect of making hydrophobic substances that are not miscible with water miscible with water.

[0045] As a water-miscible solvent, any solvent with excellent solubility in water is acceptable, and a solvent with a solubility parameter (SP value) of 7.0 or higher is preferred, with a solvent with a value of 9.0 or higher being more preferred.

[0046] Examples of water-miscible solvents include polar protic solvents such as isopropanol, ethylene glycol, propylene glycol, methanol, ethanol, propanol, butanol, glycerol, and 2-(2-aminoethoxyethanol); polar aprotic solvents such as acetone, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and acetonitrile; and nonpolar solvents such as hexane, benzene, toluene, and diethyl ether. These water-miscible solvents may be used individually or in combination of two or more.

[0047] In the etching composition of the present invention, the content of the water-miscible solvent is preferably 5.0% by mass or less, more preferably 1.0% by mass or less, of 100% by mass of the etching composition, and it is most preferable that the water-miscible solvent is not included, as this provides excellent solubility for components (A) and (B).

[0048] (Mass ratio of each component) The mass ratio of component (B) such as component (B1) to component (A) in the etching composition of the present invention (mass of component (B) (mass%) / mass of component (A) (mass%), hereinafter referred to as "(B) / (A)") is preferably 0.0010 to 2.0, more preferably 0.0050 to 1.5, and even more preferably 0.010 to 1.1, as it is excellent in protecting silicon germanium. Furthermore, from the viewpoint of selectivity, it may also be 0.2 to 5, more preferably 0.25 to 3, and even more preferably 0.3 to 1.1.

[0049] The ratio of the content (mol / L) of the azo compound (B) to the content (mol / L) of the alkaline compound (A) in the etching composition of the present invention is preferably 0.0010 to 2.0, more preferably 0.0050 to 1.5, even more preferably 0.010 to 1.0, and particularly preferably 0.05 to 0.41, as this provides excellent protection for silicon germanium.

[0050] When the etching composition of the present invention contains component (C), the mass ratio of component (A) to component (C) (mass of component (A) / mass of component (C), hereinafter referred to as "(A) / (C)") is preferably 0.0010 to 0.70, more preferably 0.0030 to 0.60, and even more preferably 0.0050 to 0.50, due to its excellent silicon solubility.

[0051] When the etching composition of the present invention contains component (C), the mass ratio of component (B), such as component (B1), to component (C) (mass of component (B) / mass of component (C), hereinafter referred to as "(B) / (C)") is preferably 0.0010 to 0.70, more preferably 0.0030 to 0.60, and even more preferably 0.0050 to 0.50, as this provides excellent protection for silicon germanium.

[0052] When etching is performed using the etching composition of the present invention, the reason for the excellent selective solubility of silicon in silicon germanium is not clear, but it is presumed to be due to the following reasons. In the etching composition, the alkali compound (A) dissolves silicon, but as a side reaction, silicon germanium is also dissolved at the same time. Radicals generated from the radical generator (B) in the etching composition extract electrons from hydrogen-terminated Si atoms in silicon germanium, generating Si radicals. The generated Si radicals are thought to react with hydroxide radicals or radicals derived from the radical generator (B) present in the etching composition, forming a film of Si oxide or the like. In this case, it is thought that the film is preferentially formed on the silicon germanium surface compared to silicon. Furthermore, since the film functions as a protective film for the etching composition, it is presumed that silicon, which does not have the film formed on it, is more selectively dissolved by the etching composition of the present invention compared to silicon germanium. In particular, when using an azo compound (B1) such as an azo initiator, it is thought that tertiary carbon radicals represented by the general formula (4) described later are generated from the azo compound (B1), and rapidly react with Si radicals on the silicon germanium surface to form a coating derived from tertiary carbon. Furthermore, it is hypothesized that the coating derived from tertiary carbon exhibits strong resistance to dissolution by alkali compounds (A) due to the high steric hindrance inherent in tertiary carbon, resulting in superior selective solubility of silicon in silicon germanium compared to other radical generators (B).

[0053] (Method for manufacturing the etching composition) The method for manufacturing the etching composition of the present invention is not particularly limited, and it can be manufactured by mixing component (A), component (B), and optionally component (C), and other components. The order of mixing is not particularly limited, and all components may be mixed at once, or some components may be mixed in advance and then the remaining components may be mixed.

[0054] (Physical properties of the etching composition) The pH of the etching composition of the present invention at 25°C is preferably 8.0 to 14, more preferably 9.0 to 14, and even more preferably 10 to 14, due to its excellent silicon solubility.

[0055] The etch rate ER of silicon in the etching composition of the present invention Ｓｉ Because it exhibits excellent selective solubility of silicon in silicon germanium, an etch rate of 50 nm / min or more is preferred, and 100 nm / min or more is more preferred. Here, the etch rate ER of silicon Ｓｉ This refers to the etch rate in single-crystal silicon, and is the value at 60°C. The etch rate of silicon can be controlled, for example, by the pH of the etching composition.

[0056] Etching rate ER of silicon germanium in the etching composition of the present invention ＳｉＧｅ Because it exhibits excellent selective solubility of silicon in silicon germanium, a flux density of 10 nm / min or less is preferred, more preferably 8.0 nm / min or less, and even more preferably 5.0 nm / min or less.

[0057] The dissolution selectivity ratio (ER) of silicon and silicon germanium in the etching composition of the present invention Ｓｉ / ER ＳｉＧｅ ) is preferable to have a value of 35 or higher because it exhibits excellent selective solubility of silicon in silicon germanium. That is, it is preferable to satisfy the following formula (7). ER Ｓｉ / ER ＳｉＧｅ ≥35 (7) The solubility selectivity ratio is more preferably 50 or higher, and even more preferably 70 or higher.

[0058] Etch rate ER Ｓｉ , Etch rate ER ＳｉＧｅ The solubility selectivity ratio is measured and calculated by the method described in the examples below.

[0059] (Etching target of the etching composition) The etching composition of the present invention suppresses the dissolution of silicon germanium, promotes the dissolution of silicon, and exhibits excellent selective dissolution of silicon relative to silicon germanium. For this reason, the etching composition of the present invention is suitable as an etching target for structures containing silicon and silicon germanium, such as semiconductor devices, and is particularly suitable for structures in which silicon and silicon germanium are laminated and used in the formation of BSPDN structures.

[0060] The silicon content in the silicon germanium to be etched is preferably 10% by mass or more, and more preferably 20% by mass or more, out of 100% by mass of silicon germanium, as this is suitable for etching with the etching composition of the present invention. The silicon content in the silicon germanium to be etched is preferably 98% by mass or less, and more preferably 95% by mass or less, out of 100% by mass of silicon germanium, as this is suitable for etching with the etching composition of the present invention.

[0061] The germanium content in the silicon germanium to be etched is preferably 2.0% by mass or more, and more preferably 5.0% by mass or more, per 100% by mass of silicon germanium, as this is suitable for etching with the etching composition of the present invention. The germanium content in the silicon germanium to be etched is preferably 90% by mass or less, and more preferably 80% by mass or less, per 100% by mass of silicon germanium, as this is suitable for etching with the etching composition of the present invention.

[0062] Silicon germanium alloy films can be manufactured by deposition using known methods. However, due to their excellent electron and hole mobility after transistor formation, silicon germanium alloy films are preferably manufactured by deposition using crystal growth methods.

[0063] Structures containing silicon and silicon germanium, or structures in which silicon and silicon germanium are layered, may have exposed silicon oxide.

[0064] (Etching Method) The etching method of the present invention is a method for etching a structure containing silicon and silicon germanium using the etching composition of the present invention.

[0065] Any known etching method can be used. Examples include batch etching and sheet etching.

[0066] The etching temperature is preferably 15°C or higher, and more preferably 20°C or higher, as this can improve the etch rate. From the viewpoint of reducing damage to the substrate and ensuring etching stability, the etching temperature is preferably 95°C or lower, and more preferably 80°C or lower. Here, the etching temperature refers to the temperature of the etching composition during etching. The lower and upper limits of the etching temperature (temperature of the etching composition) described above can be combined arbitrarily. For example, it may be 15°C to 95°C, or 20°C to 95°C.

[0067] [Etching composition according to the second embodiment] The etching composition according to the second embodiment of the present invention is an etching composition comprising an alkaline compound (A) ("component (A)") and a radical (B') ("component (B')").

[0068] (Component (B')) Component (B') in the present invention is a radical generated from component (B) described above, and component (B') is preferably an organic radical because of its high protective power for silicon germanium, and more preferably represented by the following general formula (4).

[0069] (In the above general formula (4), R 7 R 8 A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R 8 R 7 A functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may be bonded to form a ring and may have substituents, R 9(This is a functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may have substituents.)

[0070] Because silicon germanium has high protective power and is easy to use as an etching composition, in the above general formula (4), R 7 The alkyl group is preferably a C1-C6 alkyl group, and is a methyl group, an ethyl group, R 8 A cyclohexyl group or cyclopentyl group bonded to it is more preferable. 8 R 7 For the same reasons as described above, alkyl groups having 1 to 6 carbon atoms are preferred, including methyl groups, ethyl groups, propyl groups, and R 7 A cyclohexyl group or cyclopentyl group bonded to it is more preferable. 9 R 7 For the same reasons as described above, it is preferable that the functional group be selected from alkyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups having 1 to 6 carbon atoms, and more preferably that it be selected from methyl groups, ethyl groups, propyl groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups.

[0071] In the present invention, component (B') is preferably represented in the form of the following general formula (5) or (6).

[0072] (In the above general formula (5), R 7 (This is a functional group selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, which may have substituents.) (In the above general formula (6), R 7 , R 8 Each of these is independently a functional group selected from a hydrocarbon group (which may have substituents), a cyano group, a carboxyl group, an ester group, an amide group, and an amidine group.

[0073] By using the radical represented by formula (5) or (6) above as component (B') of the etching composition of the present invention, the protective power of silicon germanium is further enhanced, and an etching composition that can selectively etch silicon surfaces is more easily obtained. In the etching composition according to the second embodiment of the present invention, the details of the component (A) and optional component (C) and other components, the mass ratio of each component, the method for manufacturing the etching composition, the physical properties of the etching composition, the target of etching, the etching method, etc., can be the same as those of the etching composition according to the first embodiment of the present invention described above.

[0074] <Applications> The etching compositions and etching methods according to the first and second embodiments of the present invention can be suitably used in the manufacture of semiconductor devices that include a step of etching a structure containing silicon and silicon germanium. In particular, because they suppress the dissolution of silicon germanium, promote the dissolution of silicon, and exhibit excellent selective dissolution of silicon to silicon germanium, they are suitable for methods of manufacturing transistors that include a step of etching a structure containing silicon, and are especially suitable for methods of manufacturing transistors that include a step of etching a structure containing silicon, and are particularly suitable for the manufacture of devices having a BSPDN structure that includes a step of etching a structure containing silicon. Furthermore, because the compositions containing the alkaline compound (A) and azo compound (B1) of the present invention exhibit excellent selective dissolution of silicon to silicon germanium, it is preferable to use the compositions in etching methods that selectively etch silicon with respect to silicon germanium. Moreover, it is preferable to use compositions containing the alkaline compound (A) and azo compound (B1) in etching that selectively etches silicon with respect to silicon germanium.

[0075] The etching composition of the present invention exhibits excellent flatness of the silicon surface after etching, and can therefore be widely used as an etching composition for various applications. In particular, the etching composition of the present invention exhibits excellent selective solubility of silicon in silicon germanium. Due to these properties, the etching composition of the present invention can be suitably used in the manufacture of BSPDN. The etching method of the present invention, the semiconductor device manufacturing method of the present invention, and the transistor manufacturing method having a BSPDN structure of the present invention enable high-precision etching in the etching process, allowing for the production of desired products with a high yield.

[0076] [Composition] Embodiments of the present invention include a composition comprising a quaternary ammonium compound (A2) (hereinafter sometimes referred to as "component (A2)") and an azo compound (B2) (hereinafter sometimes referred to as "component (B2)"), wherein the azo compound (B2) has a tertiary carbon atom adjacent to the nitrogen atom forming the azo bond, and the pH is 10 or higher.

[0077] (Component (A2)) As component (A2) in the composition of the present invention, the alkaline compound (A) described in the etching composition of the first embodiment can be used in the same form. The mass ratio of component (A2) in the composition of the present invention to each of the components described below, and the method for manufacturing the composition can be the same as those used for the etching composition of the first embodiment of the present invention described above.

[0078] (Component (B2)) Component (B2) in the composition of the present invention is an azo compound in which the carbon atom adjacent to the nitrogen atom forming the azo bond is a tertiary carbon. An example of component (B2) is an azo compound represented in the form of the above general formula (1).

[0079] The pH of the composition of the present invention at 25°C is not particularly limited as long as it is 10 or higher, but is preferably 10.5 or higher, more preferably 11 or higher, and even more preferably 11.5 or higher. There is no particular upper limit to the pH of the composition of the present invention, but it should be 14 or lower.

[0080] (Component (C) and other components) In the composition of the present invention, the details of component (C) and other components that may be included as optional components, the mass ratio of each component, etc., can be the same as those of the etching composition according to the first embodiment of the present invention described above.

[0081] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples without departing from its essence.

[0082] (Raw Materials) The following materials were used as raw materials for the etching compositions in the examples and comparative examples. Ingredient (A-1): Ethyltrimethylammonium hydroxide (ETMAH) Ingredient (A-2): Tetramethylammonium hydroxide (TMAH) Ingredient (B1-1): 4,4'-Azobis(4-cyanovaleric acid) (V-501) Ingredient (B1-2): 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] (VA-061) Ingredient (B1-3): 2,2'-Azobis(2-methylpropionamidine) dihydrochloride (V-50) Ingredient (B1-4): 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate (VA-057) Ingredient (B1-5): 2,2'-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) Ingredient (B1-6): 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) Ingredient: Hydrogen peroxide (Comparative example)

[0083] <Etch Rate and Surface Flatness of Silicon> A silicon substrate with a film thickness of 0.75 mm was immersed in a 0.5% by mass hydrofluoric acid aqueous solution for 60 seconds, then rinsed with ultrapure water, and after masking half of the substrate, it was immersed at 60°C in the etching composition obtained in the examples and comparative examples. The immersion time was 5 minutes for the examples and 3 minutes for the comparative examples. The film thickness with and without masking was measured using a contact step gauge (Dektak 150, Veeco), and the etch rate ER of silicon was calculated using the following formula (8). Ｓｉ The value [nm / min] was calculated. ER Ｓｉ[nm / min] = (Silicon film thickness with masking - Silicon film thickness without masking) ÷ Immersion time (8) The surface roughness of the silicon after immersion was measured with a contact profilometer. The surface flatness was indicated by the average value of the surface roughness when measured on line segments of 1 mm in length arranged in parallel at intervals of 0.5 cm on the silicon surface.

[0084] <Etch rate of silicon germanium>A substrate with a 50-nm-thick silicon germanium layer was immersed in a 0.5 mass% hydrofluoric acid aqueous solution for 60 seconds, then rinsed with ultrapure water, and then immersed in the etching compositions obtained in the examples and comparative examples at 60 °C. The immersion time was 5 minutes for the examples and 3 minutes for the comparative examples. The film thickness before and after immersion was measured with an ellipsometer (UNISEL manufactured by Horiba), and the etch rate ER ＳｉＧｅ [nm / min] of the silicon germanium layer was calculated using the following formula (9). ER ＳｉＧｅ [nm / min] = (Silicon germanium film thickness before immersion - Silicon germanium film thickness after immersion) ÷ Immersion time (9)

[0085] <Dissolution selectivity ratio of silicon and silicon germanium>The dissolution selectivity ratio of silicon and silicon germanium was calculated using the following formula (10). Dissolution selectivity ratio = ER Ｓｉ [nm / min] ÷ ER ＳｉＧｅ [nm / min] (10)

[0086] [Example 1] In 100 mass% of the etching composition, the components were mixed so that component (A-1) was 10.5 mass%, component (B1-1) was 8.4 mass%, and water was the remainder, to obtain an etching composition. Etching was performed at 60 °C using the obtained etching composition. The evaluation results are shown in Table 1.

[0087] [Example 2] to [Example 11] The same operations as in Example 1 were performed except that the conditions such as the type and content of the components of the etching composition were changed as shown in Table 1 (Examples 2 to 7) or Table 2 (Examples 8 to 11), to obtain an etching composition. The evaluation results of the obtained etching compositions are shown in Table 1 or Table 2.

[0088] [Comparative Examples 1-2] Except for changing the types and content of the components of the etching composition as shown in Table 1, the procedure was the same as in Example 1 to obtain etching compositions. The evaluation results of the obtained etching compositions are shown in Table 1.

[0089]

[0090]

[0091] As can be seen from Table 1, the etching compositions obtained in the examples showed remarkably excellent selective solubility of silicon in silicon germanium. Furthermore, the etching compositions obtained in the examples showed excellent flatness of the silicon (100) surface after etching. On the other hand, the etching compositions obtained in the comparative examples showed poor selective solubility of silicon in silicon germanium. Furthermore, the etching compositions obtained in the comparative examples showed poor flatness of the silicon (100) surface after etching.

[0092] The etching composition of the present invention exhibits excellent selective solubility of silicon in silicon germanium. Furthermore, the etching composition of the present invention exhibits excellent flatness of the silicon (100) surface after etching. For these reasons, it is particularly suitable as an etching composition for manufacturing BSPDN structures.

Claims

1. An etching composition comprising an alkaline compound (A) and an azo compound (B1), which selectively etches silicon with respect to silicon germanium.

2. The etching composition according to claim 1, wherein the alkaline compound (A) comprises at least one compound selected from the group consisting of quaternary ammonium hydroxide compounds, amine compounds, and metal hydroxides.

3. The etching composition according to claim 2, wherein the alkaline compound (A) comprises a quaternary ammonium hydroxide compound.

4. The etching composition according to claim 1, wherein the azo compound (B1) is represented by the following general formula (1). (In the above general formula (1), R １ is a functional group selected from a hydrocarbon group which may combine with R ２ to form a ring and may have a substituent, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group, R ２ is a functional group selected from a hydrocarbon group which may combine with R １ to form a ring and may have a substituent, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group, R ４ is a functional group selected from a hydrocarbon group which may combine with R ５ to form a ring and may have a substituent, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group, R ５ is a functional group selected from a hydrocarbon group which may combine with R ４ to form a ring and may have a substituent, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group, R ３ and R ６ are each independently a functional group selected from a hydrocarbon group which may have a substituent, a cyano group, a carboxyl group, an ester group, an amide group and an amidine group.) 5. The etching composition according to claim 4, wherein the azo compound (B1) is an azo initiator.

6. The etching composition according to claim 5, wherein the azo initiator is represented in the form of the following general formula (2) or (3). (In the above general formula (2), R １ , R ４ These are functional groups selected from hydrocarbon groups, cyano groups, carboxyl groups, ester groups, amide groups, and amidine groups, each of which may independently have substituents. (In the above general formula (3), R １ , R ３ , R ４ , R ６ Each of these is independently a functional group selected from a hydrocarbon group (which may have substituents), a cyano group, a carboxyl group, an ester group, an amide group, and an amidine group.

7. The etching composition according to claim 1, wherein the content of the alkaline compound (A) in 100% by mass of the etching composition is 0.01% by mass to 40% by mass.

8. The etching composition according to claim 1, wherein the content of the azo compound (B1) in 100% by mass of the etching composition is 0.01% by mass to 20% by mass.

9. The etching composition according to claim 1, wherein the ratio of the content (mass%) of the azo compound (B1) to the content (mass%) of the alkaline compound (A) is 0.2 to 5.

10. The etching composition according to claim 1, further comprising water.

11. The etching composition according to claim 1, wherein the pH of the etching composition is 8.0 to 14.

12. The etching composition according to claim 1, wherein the temperature of the etching composition is 20°C to 95°C.

13. A composition comprising a quaternary ammonium compound (A2) and an azo compound (B2), wherein the azo compound (B2) has a tertiary carbon atom adjacent to the nitrogen atom forming the azo bond, and has a pH of 10 or higher.

14. An etching method for selectively etching a silicon surface from a structure including a silicon surface and a silicon germanium surface, using the etching composition described in claim 1.

15. A method for manufacturing a semiconductor device, comprising the step of etching a silicon-containing structure using the etching composition described in claim 1.

16. A method for manufacturing a transistor, comprising the step of etching a silicon-containing structure using the etching composition described in claim 1.

17. A method for manufacturing a transistor having a BSPDN structure, comprising the step of etching a silicon-containing structure using the etching composition described in claim 1.

18. An etching method for selectively etching silicon with respect to silicon germanium using a composition containing an alkaline compound (A) and an azo compound (B1).

19. Use of a composition containing an alkaline compound (A) and an azo compound (B1) for etching, which selectively etches silicon relative to silicon germanium.

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