Etching composition for semiconductor substrate for memory element and method for manufacturing semiconductor substrate for memory element using same

Abstract

Provided is an etching composition for a semiconductor substrate for a memory element capable of providing a semiconductor substrate for a memory element having improved performance.　The etching composition for a semiconductor substrate for a memory element comprises: (A) an oxidizing agent; (B) a fluorine compound; and (C) a metal tungsten corrosion inhibitor, wherein (C) the metal tungsten corrosion inhibitor contains at least one selected from the group consisting of an ammonium salt represented by formula (1) and a heteroaryl salt having a C14-C30 alkyl group.　

Description

Etching composition for semiconductor substrate for memory device and method for manufacturing semiconductor substrate for memory device using the same

[0001] The present invention relates to an etching composition for a semiconductor substrate for a memory device and a method for manufacturing a semiconductor substrate for a memory device using the same.

[0002] In recent years, there has been an increasing demand for further miniaturization and higher performance of memory elements, and technological developments such as miniaturization of semiconductor substrates and three-dimensional integration are progressing.

[0003] Metallic tungsten is a suitable material for semiconductor substrates, which enable the miniaturization and high performance of such memory elements. Metallic tungsten can be deposited by CVD (chemical vapor deposition) and has characteristics such as low electromigration, low electrical resistance, and high heat resistance. For this reason, metallic tungsten is used for buried word lines in memory elements such as DRAMs.

[0004] It is known that the buried word line can be manufactured, for example, by the following method. Specifically, a silicon dioxide film, a titanium-containing film (barrier film) containing titanium and / or a titanium alloy, and a metallic tungsten film are sequentially formed on a silicon substrate having a recess formed by etching. The surface is then planarized by CMP (chemical mechanical polishing), and the titanium-containing film and the metallic tungsten film, or the metallic tungsten film, are selectively etched by dry etching or the like (CMP may be omitted). The titanium-containing film is then selectively etched to manufacture the buried word line of the memory element (Non-Patent Document 1).

[0005] Thus, the method for manufacturing a semiconductor substrate for a memory element includes a step of selectively removing titanium or a titanium alloy without damaging the tungsten metal (a selective etching step of titanium and titanium alloy). Therefore, when manufacturing a small, highly functional memory element using tungsten metal, an etching composition that etches the titanium and titanium alloy (having a high Ti / W etching selectivity) without etching the tungsten metal is required.

[0006] SPCC 2019 Technical Program, "Wet Etchant for DRAM Word-line Titanium Nitride Recess with Selectivity to Tungsten", Wilson et al., [https: / / www.linx-consulting.com / wp-content / uploads / 2019 / 04 / 03-15-W_Yeh-Dupont-Wet_Etchant_for_DRAM_Word_line_TiN_Recess_with_Selectivity_to_W.pdf]

[0007] However, it has been found that even if a semiconductor substrate for a memory element using metallic tungsten as a material is manufactured using a conventional etching composition, a memory element with the desired performance may not be obtained.

[0008] Therefore, the present invention provides an etching composition that can provide a semiconductor substrate for a memory device with improved performance.

[0009] The present invention provides, for example, the following etching composition.

[0010] [1] An etching composition for a semiconductor substrate for a memory element, comprising (A) an oxidizing agent, (B) a fluorine compound, and (C) a metal tungsten corrosion inhibitor, wherein the metal tungsten corrosion inhibitor (C) is represented by the following formula (1): (In the above formula (1), R １ is a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms; R ２[2] An etching composition for a semiconductor substrate for a memory element, comprising at least one selected from the group consisting of ammonium salts represented by the formula (I) and heteroaryl salts having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, wherein each of R is independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and X is a halide ion, a hydroxide ion, an organic sulfonate ion, a tetrafluoroborate anion, or a hexafluorophosphate anion. １ is a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms. [3] The etching composition for a semiconductor substrate for a memory element according to the above [1]. １ is a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 20 carbon atoms. [4] The etching composition for a semiconductor substrate for a memory element according to any one of [1] to [3] above, having a surface tension of 50 mN / m or less. [5] The etching composition for a semiconductor substrate for a memory element according to any one of [1] to [4] above, further comprising (D) a pH adjuster. [6] The etching composition for a semiconductor substrate for a memory element according to any one of [1] to [5] above, having a pH of 0.1 to 5.0. [7] The etching composition for a semiconductor substrate for a memory element according to any one of [1] to [6] above, further comprising (E) an organic solvent. [8] The etching composition for a semiconductor substrate for a memory element according to [7] above, wherein the (E) organic solvent is an alcohol. [9] A method for producing a semiconductor substrate for a memory element, comprising a step of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy and a metal tungsten film with the etching composition for a semiconductor substrate for a memory element according to any one of [1] to [8] above, to remove at least a portion of the titanium-containing film.

[0011] According to the present invention, there is provided an etching composition for a semiconductor substrate for a memory device, which can provide a semiconductor substrate for a memory device with improved performance.

[0012] It is a schematic diagram of an etching process of a semiconductor substrate for a memory element, a schematic diagram of an evaluation sample (before etching) used in Examples, and a schematic diagram of an evaluation sample (after etching) used in Examples.

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] <Etching Composition for Memory Element Semiconductor Substrates> The etching composition for memory element semiconductor substrates according to the present invention comprises (A) an oxidizing agent, (B) a fluorine compound, and (C) a metal tungsten corrosion inhibitor, wherein (C) the metal tungsten corrosion inhibitor comprises at least one selected from the group consisting of ammonium salts represented by the following formula (1) and heteroaryl salts having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms:

[0015]

[0016] In the above formula (1), R １ is a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms. ２ are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. Furthermore, X is a halide ion, a hydroxide ion, an organic sulfonate ion, a tetrafluoroborate anion, or a hexafluorophosphate anion.

[0017] By using the etching composition, a semiconductor substrate for a memory device having improved performance can be provided. The present invention will be described below with reference to the drawings. Note that the drawings may be exaggerated for illustrative purposes and may differ from the actual dimensions.

[0018] FIG. 1 is a schematic diagram of an etching process for a semiconductor substrate for a memory device. The semiconductor substrate for a memory device (before etching) 10 includes a silicon substrate 11 having a recess, an insulating film 12 made of silicon dioxide, a barrier film (before etching) 13 made of titanium nitride, and a metallic tungsten film 14. Such a semiconductor substrate for a memory device (before etching) 10 can be manufactured by sequentially depositing an insulating film made of silicon dioxide, a barrier film made of titanium nitride, and a metallic tungsten film on a silicon substrate having a recess, followed by planarization by CMP (chemical mechanical polishing) and selective etching of the barrier film and the metallic tungsten film by dry etching or the like (CMP may be omitted). While the semiconductor substrate for a memory device (before etching) 10 shown in FIG. 1 has both the barrier film and the metallic tungsten film selectively etched by dry etching, it is also possible to configure the semiconductor substrate for a memory device (before etching) 10 by selectively etching only the metallic tungsten film by dry etching.

[0019] By applying an etching composition for a semiconductor substrate for a memory device to a semiconductor substrate for a memory device (before etching) 10, a semiconductor substrate for a memory device (after etching) 20 can be obtained. Specifically, when the etching composition for a semiconductor substrate for a memory device is applied to the semiconductor substrate for a memory device (before etching) 10, the barrier film (before etching) 13 made of titanium nitride is selectively etched to form a barrier film 23 made of titanium nitride. On the other hand, the metallic tungsten film 14 is not etched (corroded) or is barely etched (corroded) to form a metallic tungsten film 24.

[0020] However, when a conventional etching composition for a semiconductor substrate for a memory device is used, the above-described semiconductor substrate for a memory device (after etching) 20 cannot be obtained, and instead, a semiconductor substrate for a memory device (after etching) 30 may be obtained. Specifically, when the etching composition for a semiconductor substrate for a memory device is applied to a semiconductor substrate for a memory device (before etching) 10 for a memory device, etching (corrosion) of the metallic tungsten film 14 may proceed along with etching of the barrier film (before etching) 13 made of titanium nitride. As a result, the metallic tungsten film 34 of the semiconductor substrate for a memory device (after etching) 30 has a corroded metallic tungsten film surface 34c. A memory device manufactured using a semiconductor substrate for a memory device (after etching) 30 in which the corroded metallic tungsten film has occurred may not exhibit the desired physical properties.

[0021] The reason for the progression of the etching (corrosion) of the metal tungsten film described above is not entirely clear, but the following reason is considered. That is, conventional etching compositions for semiconductor substrates for memory devices typically contain a metal tungsten anticorrosive. Therefore, it is believed that the titanium nitride barrier film (before etching) 13 can be selectively etched without etching (corroding) the metal tungsten film 14. However, as the selective etching of the titanium nitride barrier films 13, 23 progresses, the side surface 24b of the metal tungsten film is exposed. In this case, a small gap (e.g., approximately 1 to 5 nm) is formed between the side surface 24b of the metal tungsten film, the surface of the insulating film 22, and the top surface of the barrier film 23. Compared to the oxidizer and fluorine compound, which are involved in etching and have relatively small molecular sizes, the metal tungsten anticorrosive, which has a large molecular size, is expected to have difficulty penetrating the gap. That is, in this gap, the concentration of the metal tungsten anticorrosive is relatively lower than the concentrations of the oxidizer and the fluorine compound, so that before the anti-etching function of the metal tungsten anticorrosive contained in the etching composition is exerted, etching (corrosion) of the metal tungsten film side surface 24b can proceed. As such, it is presumed that etching (corrosion) from the direction of the metal tungsten film side surface 24b occurs, and the metal tungsten film 34 of the memory element semiconductor substrate (after etching) 30 has a metal tungsten film corroded surface 34c with a sloped shape. That is, although the conventional etching composition for memory element semiconductor substrates can suppress or prevent etching (corrosion) from the direction of the metal tungsten film surface 24a by the contained metal tungsten anticorrosive, it sometimes cannot sufficiently prevent etching (corrosion) from the direction of the metal tungsten film side surface 24b exposed by selective etching of the barrier film 13 made of titanium nitride.

[0022] In contrast, the etching composition for semiconductor substrates for memory devices according to the present invention contains a predetermined metal tungsten anticorrosive, which prevents not only etching (corrosion) from the metal tungsten film surface 24a but also etching (corrosion) from the metal tungsten film side surface 24b. Specifically, the predetermined metal tungsten anticorrosive can be adsorbed to the metal tungsten film side surface 24b, which becomes exposed as the selective etching of the titanium nitride barrier film 13 progresses, faster than etching (corrosion) occurs. As a result, a semiconductor substrate for memory devices can be manufactured that has no or almost no corroded metal tungsten film surface 34c.

[0023] In this specification, the term "titanium alloy" refers to a material having metallic properties, which is titanium alloyed with one or more metal or nonmetal elements other than titanium. The titanium alloy contains 20 atomic weight percent or more, preferably 30 atomic weight percent or more, more preferably 35 atomic weight percent or more, and even more preferably 40 to 99.9 atomic weight percent of the total atomic weight of the titanium alloy. Elements other than titanium that can be contained in titanium alloys include aluminum, oxygen, nitrogen, carbon, molybdenum, vanadium, niobium, iron, chromium, nickel, tin, hafnium, zirconium, palladium, ruthenium, and platinum. These elements other than titanium may be contained alone or in combination.

[0024] Hereinafter, the etching composition for semiconductor substrates for memory devices according to the present invention will be described in detail.

[0025] [(A) Oxidizing Agent] The (A) oxidizing agent has a function of changing the oxidation number of titanium in titanium or titanium alloys to tetravalent.

[0026] (A) The oxidizing agent is not particularly limited, but includes peracids, halogen oxoacids, and salts thereof.

[0027] Examples of the peracid include hydrogen peroxide, persulfuric acid, percarbonic acid, perphosphoric acid, peracetic acid, perbenzoic acid, and metachloroperbenzoic acid.

[0028] Examples of the halogen oxoacids include oxoacids of chlorine such as hypochlorous acid, chlorous acid, chloric acid, and perchloric acid; oxoacids of bromine such as hypobromous acid, bromous acid, bromic acid, and perbromic acid; and oxoacids of iodine such as hypoiodous acid, iodous acid, iodic acid, and periodic acid.

[0029] Examples of the salts include alkali metal salts of the peracids or halogen oxoacids, such as lithium salts, sodium salts, potassium salts, rubidium salts, and cesium salts; alkaline earth metal salts of the peracids or halogen oxoacids, such as beryllium salts, magnesium salts, calcium salts, strontium salts, and barium salts; metal salts of the peracids or halogen oxoacids, such as aluminum salts, copper salts, zinc salts, and silver salts; and ammonium salts of the peracids or halogen oxoacids.

[0030] The oxidizing agent (A) is preferably hydrogen peroxide or an oxoacid of iodine, more preferably hydrogen peroxide, iodic acid, or periodic acid, still more preferably iodic acid or periodic acid, and is particularly preferably iodic acid from the viewpoint of being able to further increase the Ti / W etching selectivity (etching amount of titanium / titanium alloy / etching amount (amount of corrosion) of metallic tungsten).

[0031] The oxidizing agent (A) may be used alone or in combination of two or more. That is, in one embodiment, the oxidizing agent (A) preferably contains at least one selected from the group consisting of peracids, halogen oxoacids, and salts thereof, more preferably contains at least one selected from the group consisting of hydrogen peroxide and iodine oxoacids, further preferably contains at least one selected from the group consisting of hydrogen peroxide, iodic acid, and periodic acid, particularly preferably contains at least one selected from the group consisting of iodic acid and periodic acid, and most preferably contains periodic acid.

[0032] The addition rate of the oxidizing agent (A) is preferably 0.0001 to 10 mass %, more preferably 0.001 to 5 mass %, even more preferably 0.003 to 3 mass %, and particularly preferably 0.01 to 2 mass %, relative to the total mass of the etching composition for semiconductor substrates for memory elements.

[0033] [(B) Fluorine Compound] (B) Fluorine compound has a function of promoting etching of tetravalent titanium and titanium alloys.

[0034] The (B) fluorine compound is not particularly limited, but examples thereof include hydrogen fluoride (HF), tetrafluoroboric acid (HBF ４ ), hexafluorosilicic acid (H ２ SiF ６ ), hexafluorozirconate (H ２ ZrF ６ ), hexafluorotitanic acid (H ２ TiF ６ ), hexafluorophosphate (HPF ６ ), hexafluoroaluminic acid (H ２ AlF ６ ), hexafluorogermanic acid (H ２ GeF ６ ), and salts thereof.

[0035] In this case, the salt is ammonium fluoride (NH ４ F), ammonium fluoride (NH ４ F HF), ammonium tetrafluoroborate (NH ４ BF ４ ), ammonium hexafluorosilicate ((NH ４ ) ２ SiF ６ ), tetramethylammonium tetrafluoroborate (N(CH ３ ) ４ BF ４ ) and the like.

[0036] Among the above, (B) fluorine compounds include hydrogen fluoride (HF), tetrafluoroboric acid (HBF ４ ), hexafluorosilicic acid (H ２ SiF ６ ), and salts thereof, and hydrogen fluoride (HF), ammonium fluoride (NH ４ F), ammonium fluoride (NH ４ F HF), hexafluorosilicic acid (H ２ SiF６ ) is more preferable, and from the viewpoints of being able to further prevent corrosion of metallic tungsten and to further increase the Ti / W etching selectivity, acid ammonium fluoride (NH ４ F HF), hexafluorosilicic acid (H ２ SiF ６ ) is more preferred, and hexafluorosilicic acid (H ２ SiF ６ ) is particularly preferred.

[0037] The fluorine compound (B) may be used alone or in combination of two or more. That is, in a preferred embodiment, the fluorine compound (B) is hydrogen fluoride (HF), tetrafluoroboric acid (HBF ４ ), hexafluorosilicic acid (H ２ SiF ６ ), hexafluorozirconate (H ２ ZrF ６ ), hexafluorotitanic acid (H ２ TiF ６ ), hexafluorophosphate (HPF ６ ), hexafluoroaluminic acid (H ２ AlF ６ ), hexafluorogermanic acid (H ２ GeF ６ ), and salts thereof, and ４ ), hexafluorosilicic acid (H ２ SiF ６ ), and salts thereof, and more preferably contains at least one selected from the group consisting of hydrogen fluoride (HF), ammonium fluoride (NH ４ F), ammonium fluoride (NH ４ F HF), and hexafluorosilicic acid (H ２ SiF ６ ), and ammonium fluoride (NH ４ F HF) and hexafluorosilicic acid (H ２ SiF ６) and hexafluorosilicic acid (H ２ SiF ６ ) is most preferred.

[0038] The addition rate of the (B) fluorine compound is preferably 0.005 to 10 mass %, more preferably 0.01 to 3 mass %, even more preferably 0.01 to 1 mass %, and particularly preferably 0.03 to 0.5 mass %, relative to the total mass of the etching composition for semiconductor substrates for memory elements.

[0039] [(C) Metallic Tungsten Corrosion Inhibitor] The (C) metallic tungsten corrosion inhibitor has the function of rapidly adsorbing not only to ordinary metallic tungsten but also to the side surfaces of metallic tungsten exposed as a result of etching of an adjacent titanium-containing film containing titanium and / or a titanium alloy, thereby reducing the reactivity of the side surfaces of the metallic tungsten and suitably preventing or suppressing etching (corrosion) from the side surfaces of the metallic tungsten.

[0040] The (C) metallic tungsten corrosion inhibitor is not particularly limited, but includes at least one selected from the group consisting of ammonium salts represented by the following formula (1) and heteroaryl salts having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms:

[0041]

[0042] In the above formula (1), R １ is a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms.

[0043] Examples of the alkyl group having 14 to 30 carbon atoms include, but are not limited to, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a docosyl group, a tetracosyl group, a hexacosyl group, an octacosyl group, and a triacontyl group.

[0044] When a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms has a substituent (a substituted alkyl group having 14 to 30 carbon atoms), the substituent is not particularly limited, but examples include halogen atoms such as fluorine, chlorine, bromine, and iodine; aryl groups having 6 to 20 carbon atoms such as phenyl and naphthyl; alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, and propyloxy; hydroxy groups; cyano groups; and nitro groups. The substituent may be one or more. Furthermore, a substituted alkyl group having 14 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the alkyl group is 14 to 30. That is, in the case of a substituted alkyl group having 14 to 30 carbon atoms, the number of carbon atoms in the alkyl group can be 14 or less, depending on the number of carbon atoms in the substituent (for example, an alkyl group having 8 to 13 carbon atoms such as an octyl group, a decyl group, or a dodecyl group).

[0045] The alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms is —(C ｎ H ２ｎ -Z-) ｍ -R ３ In this case, n is independently 1 to 5, preferably 1 to 3, and more preferably 1 to 2. m is independently 1 to 5, preferably 1 to 2. Z is independently an oxygen atom (O), a sulfur atom (S), or a phosphorus atom (P), and is preferably an oxygen atom (O). R ３ is an alkyl group having 1 to 30 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group.

[0046] When the substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms has a substituent (a substituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms), the substituent is not particularly limited, and examples thereof include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; aryl groups having 6 to 20 carbon atoms such as phenyl group and naphthyl group; alkoxy groups having 1 to 6 carbon atoms such as methoxy group, ethoxy group, and propyloxy group; hydroxy group; cyano group; and nitro group. The substituent is usually R ３ and a hydrogen atom of the alkyl(poly)heteroalkylene group is substituted with the hydrogen atom of the substituent. The group may have one or more substituents. Furthermore, a substituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the alkyl(poly)heteroalkylene group is 14 to 30. That is, in the case of a substituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, the number of carbon atoms in the alkyl(poly)heteroalkylene group can be 14 or less (for example, an alkyl group having 8 to 13 carbon atoms such as an octyl group, a decyl group, or a dodecyl group) depending on the number of carbon atoms in the substituent.

[0047] The aryl(poly)heteroalkylene group having 14 to 30 carbon atoms is —(C ｎ H ２ｎ -Z-) ｍ -Ar. In this case, each n is independently 1 to 5, preferably 1 to 3, and more preferably 1 or 2. m is 1 to 5, and preferably 1 or 2. Each Z is independently an oxygen atom (O), a sulfur atom (S), or a phosphorus atom (P), and is preferably an oxygen atom (O). Ar is an aryl group having 6 to 18 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group.

[0048] When a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms has a substituent (a substituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms), the substituent is not particularly limited, and examples thereof include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; alkyl groups having 1 to 10 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, and 1,1,3,3-tetramethylbutyl; alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, and propyloxy; hydroxy groups; cyano groups; and nitro groups. The substituents typically replace hydrogen atoms in Ar. The group may have one or more substituents. Furthermore, a substituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the aryl(poly)heteroalkylene group is 14 to 30. That is, in the case of a substituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms, the number of carbon atoms in the aryl(poly)heteroalkylene group can be 14 or less (for example, an alkyl group having 8 to 13 carbon atoms such as an octyl group, a decyl group, or a dodecyl group) depending on the number of carbon atoms in the substituent.

[0049] In one embodiment, R １ is preferably a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms, more preferably a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 20 carbon atoms, still more preferably a substituted or unsubstituted aryl(poly)heteroalkylene group having 16 to 20 carbon atoms, particularly preferably a substituted or unsubstituted aryl(poly)heteroalkylene group having 18 to 20 carbon atoms, and is preferably p-(1,1,3,3-tetramethylbutyl)phenyldi(oxyethylene)(p-CH ３ C(CH ３ ) ２ CH ２ C(CH ３ ) ２ -Ph-(O-C ２ H ４ ) ２-) group is most preferred.

[0050] In another embodiment, R １ is preferably a substituted or unsubstituted alkyl group having 14 to 25 carbon atoms or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 25 carbon atoms, more preferably a substituted or unsubstituted alkyl group having 14 to 20 carbon atoms or a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 20 carbon atoms, and is preferably a tetradecyl group, a hexadecyl group, an octadecyl group, p-(1,1,3,3-tetramethylbutyl)phenyldi(oxyethylene)(p-CH ３ C(CH ３ ) ２ CH ２ C(CH ３ ) ２ -Ph-(O-C ２ H ４ ) ２ -) group is more preferred, and a hexadecyl group, an octadecyl group, a p-(1,1,3,3-tetramethylbutyl)phenyldi(oxyethylene) (p-CH ３ C(CH ３ ) ２ CH ２ C(CH ３ ) ２ -Ph-(O-C ２ H ４ ) ２ -) group is particularly preferred, and p-(1,1,3,3-tetramethylbutyl)phenyldi(oxyethylene) (p-CH ３ C(CH ３ ) ２ CH ２ C(CH ３ ) ２ -Ph-(O-C ２ H ４ ) ２ -) group is most preferred.

[0051] Also, R ２ are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.

[0052] Examples of the alkyl group having 1 to 30 carbon atoms include, but are not limited to, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group.

[0053] When a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms has a substituent (a substituted alkyl group having 1 to 30 carbon atoms), examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; aryl groups having 6 to 20 carbon atoms such as a phenyl group and a naphthyl group; alkoxy groups having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, and a propyloxy group; a hydroxy group; a cyano group; and a nitro group. The number of substituents may be one or two or more. Furthermore, a substituted alkyl group having 1 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the alkyl group is 1 to 30.

[0054] The aryl group having 6 to 30 carbon atoms is not particularly limited, but examples thereof include a phenyl group, a naphthyl group, and a biphenyl group.

[0055] When a substituted or unsubstituted aryl group having 6 to 30 carbon atoms has a substituent (a substituted aryl group having 6 to 30 carbon atoms), examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, and an isopropyl group; alkoxy groups having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, and a propyloxy group; a hydroxy group; a cyano group; and a nitro group. The number of substituents may be one or two or more. Furthermore, a substituted aryl group having 6 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the alkyl group is 6 to 30.

[0056] Of these, R ２is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, more preferably a methyl group, ethyl group, propyl group, isopropyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, benzyl group, hydroxymethyl group, or 2-hydroxyethyl group, even more preferably a methyl group, ethyl group, benzyl group, or 2-hydroxyethyl group, particularly preferably a methyl group or a benzyl group, and most preferably a methyl group. ２ is preferably an alkyl group having 1 to 10 carbon atoms substituted with an aryl group having 6 to 20 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms substituted with a phenyl group, further preferably a benzyl group or a phenylethyl group, and particularly preferably a benzyl group.

[0057] X is a halide ion (fluoride ion, chloride ion, bromide ion, iodide ion, etc.), hydroxide ion, organic sulfonate ion (methanesulfonate ion, p-toluenesulfonate ion, etc.), tetrafluoroborate anion, or hexafluorophosphate anion. Of these, X is preferably a halide ion, and more preferably a chloride ion or bromide ion.

[0058] R １is a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, specific examples of the ammonium salt represented by formula (1) include ammonium salts having a tetradecyl group, such as tetradecyltrimethylammonium bromide and benzyldimethyltetradecylammonium chloride; ammonium salts having a hexadecyl group, such as hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium p-toluenesulfonate, hexadecyltrimethylammonium hydroxide, ethylhexadecyldimethylammonium chloride, ethylhexadecyldimethylammonium bromide and benzyldimethylhexadecylammonium chloride; and ammonium salts having an octadecyl group, such as trimethyloctadecylammonium chloride, trimethyloctadecylammonium bromide, dimethyldioctadecylammonium chloride, dimethyldioctadecylammonium bromide and benzyldimethyloctadecylammonium chloride.

[0059] R １ Specific examples of the ammonium salt represented by formula (1), in which is a substituted or unsubstituted alkyl(poly)heteroalkylene group having 14 to 30 carbon atoms, include trimethylpropyldi(oxyethylene)ammonium chloride, trimethylpropyloxyethylenethioethyleneammonium chloride, etc.

[0060] R １ Specific examples of the ammonium salt represented by formula (1), in which is a substituted or unsubstituted aryl(poly)heteroalkylene group having 14 to 30 carbon atoms, include benzyldimethyl-2-{2-[4-(1,1,3,3-tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride (benzethonium chloride), benzyldimethylphenyldi(oxyethylene)ammonium chloride, and the like.

[0061] Furthermore, examples of heteroaryl salts having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms include, but are not limited to, salts of heteroaryl cations in which at least one nitrogen atom in a substituted or unsubstituted nitrogen-atom-containing heteroaryl ring is bonded to a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms.

[0062] The nitrogen atom-containing heteroaryl ring is not particularly limited, but examples thereof include imidazole, pyrazole, oxazole, isoxazole (isoxazole), thiazole, isothiazole, pyridine, pyrazine, pyridazine, pyrimidine, quinoline, and isoquinoline rings.

[0063] In this case, when the nitrogen atom-containing heteroaryl ring has a substituent, examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group, and isopropyl group; aryl groups having 6 to 20 carbon atoms such as phenyl group and naphthyl group; alkoxy groups having 1 to 6 carbon atoms such as methoxy group, ethoxy group, and propyloxy group; hydroxy group; cyano group; and nitro group.

[0064] Examples of the alkyl group having 14 to 30 carbon atoms include, but are not limited to, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a docosyl group, a tetracosyl group, a hexacosyl group, an octacosyl group, and a triacontyl group.

[0065] When a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms has a substituent (a substituted alkyl group having 14 to 30 carbon atoms), examples of the substituent include halogen atoms such as fluorine, chlorine, bromine, and iodine; alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, propyl, and isopropyl; aryl groups having 6 to 20 carbon atoms such as phenyl and naphthyl; alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, and propyloxy; hydroxy groups; cyano groups; and nitro groups. The substituent may be one or more. Furthermore, a substituted alkyl group having 14 to 30 carbon atoms means that the total number of carbon atoms in the substituent and the alkyl group is 14 to 30. That is, in the case of a substituted alkyl group having 14 to 30 carbon atoms, the number of carbon atoms in the alkyl group can be 14 or less, depending on the number of carbon atoms in the substituent (for example, an alkyl group having 8 to 13 carbon atoms such as an octyl group, a decyl group, or a dodecyl group).

[0066] Of these, the substituted or unsubstituted alkyl group having 14 to 30 carbon atoms is preferably a substituted or unsubstituted alkyl group having 14 to 20 carbon atoms, more preferably an alkyl group having 14 to 20 carbon atoms, further preferably a tetradecyl group, a hexadecyl group, or an octadecyl group, and particularly preferably a hexadecyl group or an octadecyl group.

[0067] The counter anion of a heteroaryl cation having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms is not particularly limited, and examples thereof include halide ions such as fluoride ion, chloride ion, bromide ion, and iodide ion; hydroxide ion; organic sulfonate ions such as methanesulfonate ion and p-toluenesulfonate ion; tetrafluoroborate anion; and hexafluorophosphate anion. Among these, the counter anion is preferably a halide ion, and more preferably a chloride ion or a bromide ion.

[0068] Specific examples of heteroaryl salts having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms include imidazolium salts such as 1-tetradecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium bromide, 1-hexadecyl-3-methylimidazolium chloride, 1-hexadecyl-3-methylimidazolium bromide, 1-octadecyl-3-methylimidazolium chloride, and 1-octadecyl-3-methylimidazolium bromide; oxazolium salts such as 3-tetradecyloxazolium chloride, 3-hexadecyloxazolium chloride, and 3-octadecyloxazolium chloride; and 3-tetradecylthiazolium chloride, 3-hexadecylthiazolium chloride, and 3-octadecylthiazolium chloride. Examples of suitable thiazolium salts include pyridinium salts such as 1-tetradecylpyridinium chloride, 1-tetradecylpyridinium bromide, 1-hexadecylpyridinium chloride, 1-hexadecylpyridinium bromide, 1-octadecylpyridinium chloride, and 1-octadecylpyridinium bromide; pyrimidinium salts such as 1-tetradecylpyrimidinium chloride, 1-hexadecylpyrimidinium chloride, and 1-octadecylpyrimidinium chloride; quinolinium salts such as tetradecylquinolinium chloride, hexadecylquinolinium chloride, and octadecylquinolinium chloride; and isoquinolinium salts such as tetradecylisoquinolinium chloride, hexadecylisoquinolinium chloride, and octadecylisoquinolinium chloride. These may also be used as hydrates.

[0069] Among these, (C) the metal tungsten corrosion inhibitor is preferably an ammonium salt represented by formula (1) from the viewpoint of being able to further increase the Ti / W etching selectivity, and the ammonium salt represented by formula (1) (wherein R １ is a substituted or unsubstituted alkyl group having 15 to 20 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group having 15 to 20 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 15 to 20 carbon atoms), and more preferably an ammonium salt represented by formula (1) (wherein R １is an alkyl group having 17 to 20 carbon atoms, or a substituted aryl(poly)heteroalkylene group having 17 to 20 carbon atoms), and an ammonium salt represented by formula (1) (where R １ is a substituted aryl(poly)heteroalkylene group having 17 to 20 carbon atoms), and benzethonium chloride and benzethonium bromide are most preferred.

[0070] The above-mentioned (C) metallic tungsten corrosion inhibitor may be used alone or in combination of two or more thereof. That is, in a preferred embodiment, the (C) metallic tungsten corrosion inhibitor preferably contains at least one ammonium salt represented by formula (1), and the ammonium salt represented by formula (1) (wherein R １ is a substituted or unsubstituted alkyl group having 15 to 20 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group having 15 to 20 carbon atoms, or a substituted or unsubstituted aryl(poly)heteroalkylene group having 15 to 20 carbon atoms), and more preferably contains at least one of the ammonium salts represented by formula (1) (wherein R １ is an alkyl group having 17 to 20 carbon atoms, or a substituted aryl(poly)heteroalkylene group having 17 to 20 carbon atoms), and １ is a substituted aryl(poly)heteroalkylene group having 17 to 20 carbon atoms), and most preferably includes at least one of benzethonium chloride and benzethonium bromide.

[0071] The addition rate of the (C) metal tungsten anticorrosive is preferably 0.0001 to 5 mass %, more preferably 0.001 to 1 mass %, even more preferably 0.003 to 0.5 mass %, and particularly preferably 0.004 to 0.08 mass %, relative to the total mass of the etching composition for semiconductor substrates for memory elements.

[0072] [(D) pH Adjuster] The etching composition for a semiconductor substrate for a memory element may contain (D) a pH adjuster as necessary. In one embodiment, the etching composition for a semiconductor substrate for a memory element preferably further contains (D) a pH adjuster.

[0073] As the (D) pH adjuster, for example, an acid or alkali other than the (A) oxidizing agent and the (B) fluorine compound can be used.

[0074] Examples of the acid include hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 10-camphorsulfonic acid, and salts thereof. In this case, examples of the salt include ammonium salts such as ammonium chloride, ammonium bromide, ammonium iodide, ammonium sulfate, and ammonium nitrate; and alkylammonium salts such as methylamine hydrochloride, dimethylamine hydrochloride, dimethylamine hydrobromide, and methylamine sulfate.

[0075] Examples of the alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, ammonia, and triethylamine.

[0076] Of the above, the (D) pH adjuster is preferably hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, methanesulfonic acid, or ammonia, more preferably hydrogen chloride, sulfuric acid, or methanesulfonic acid, and from the viewpoints of being able to further prevent corrosion of metallic tungsten and to further increase the Ti / W etching selectivity, etc., hydrogen chloride or methanesulfonic acid is even more preferable, and methanesulfonic acid is particularly preferable.

[0077] The pH adjusters (D) may be used alone or in combination of two or more. That is, in a preferred embodiment, the pH adjuster (D) preferably contains at least one selected from the group consisting of hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, methanesulfonic acid, and ammonia, more preferably contains at least one selected from the group consisting of hydrogen chloride, sulfuric acid, and methanesulfonic acid, further preferably contains at least one selected from the group consisting of hydrogen chloride and methanesulfonic acid, and particularly preferably contains methanesulfonic acid.

[0078] The addition rate of the (D) pH adjuster varies depending on the pH of the etching composition for semiconductor substrates for memory elements before adjustment, but is preferably 0.0001 to 5 mass %, more preferably 0.01 to 3 mass %, even more preferably 0.1 to 1 mass %, and particularly preferably 0.3 to 0.75 mass %, relative to the total mass of the etching composition for semiconductor substrates for memory elements.

[0079] [Water] The etching composition for a semiconductor substrate for a memory element preferably contains water. The water has the function of uniformly dispersing each component contained in the etching composition for a semiconductor substrate for a memory element, the function of diluting the component, etc.

[0080] The water is not particularly limited, but is preferably water from which metal ions, organic impurities, particle particles, etc. have been removed by distillation, ion exchange treatment, filtration, various adsorption treatments, etc., more preferably pure water, and particularly preferably ultrapure water.

[0081] The water addition rate is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 90 to 99.5% by mass, based on the total mass of the etching composition for semiconductor substrates for memory elements.

[0082] [(E) Organic Solvent] The etching composition for a semiconductor substrate for a memory element may contain an organic solvent (E) as needed. In one embodiment, the etching composition for a semiconductor substrate for a memory element preferably further contains an organic solvent (E). The organic solvent (E) further reduces the surface tension of the etching composition for a semiconductor substrate for a memory element, thereby making it easier for the metal tungsten anticorrosive to penetrate into minute spaces on the side of the metal tungsten film that are generated as the selective etching of a titanium-containing film (barrier film) containing titanium or a titanium alloy progresses, and is thought to have the function of suitably preventing or suppressing etching (corrosion) from the side of the metal tungsten.

[0083] The organic solvent (E) is not particularly limited, but examples thereof include alcohols such as monoalcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, tert-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, etc.), diols (ethylene glycol, propylene glycol, neopentyl glycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethylhexane-1,3-diol, etc.), and polyhydric alcohols (glycerin, etc.); ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, and 1,4-dioxane; diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Examples of the glycol ether include glycol ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether, tripropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, and propylene glycol phenyl ether; and amides such as dimethylformamide, diethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0084] Of these, the organic solvent (E) is preferably an alcohol from the viewpoint of a high boiling point and stability, more preferably a monoalcohol or a diol, more preferably 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1,2-hexanediol, 1,6-hexanediol, or 2-ethylhexane-1,3-diol, still more preferably 1-hexanol, 1-heptanol, 1-octanol, or 2-ethylhexane-1,3-diol, and particularly preferably 1-hexanol, 1-heptanol, or 1-octanol.

[0085] The organic solvent (E) may be used alone or in combination of two or more thereof. That is, in a preferred embodiment, the organic solvent (E) preferably contains at least one alcohol, more preferably contains at least one selected from the group consisting of monoalcohols and diols, further preferably contains at least one selected from the group consisting of 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1,2-hexanediol, 1,6-hexanediol, and 2-ethylhexane-1,3-diol, particularly preferably contains at least one selected from the group consisting of 1-hexanol, 1-heptanol, 1-octanol, and 2-ethylhexane-1,3-diol, and most preferably contains at least one selected from the group consisting of 1-hexanol, 1-heptanol, and 1-octanol.

[0086] The addition rate of (E) the organic solvent varies depending on the composition, surface tension, etc. of the etching composition for semiconductor substrates for memory elements before adjustment, but is preferably 50 mass % or less, more preferably 10 mass % or less, still more preferably 0.01 to 7.5 mass %, particularly preferably 0.05 to 5 mass %, and most preferably 0.5 to 3 mass %, relative to the total mass of the etching composition for semiconductor substrates for memory elements.

[0087] [Iodine Scavenger] When the oxidizing agent (A) contains an oxoacid of iodine, the etching composition for a semiconductor substrate for a memory element preferably further contains an iodine scavenger.

[0088] The iodine scavenger is not particularly limited, but examples thereof include acetone, butanone, 2-methyl-2-butanone, 3,3-dimethyl-2-butanone, 4-hydroxy-2-butanone, 2-pentanone, 3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone, 2-methyl-3-pentanone, 5-methyl-3-pentanone, 2,4-dimethyl-3-pentanone, 5-hydroxy-2-pentanone, 4-hydroxy-4-methyl-2-pentanone, 2-hexanone, 3-hexanone, 2-heptanone, 3-heptanone, 4 Examples of the iodine scavenger include aliphatic ketones such as 4-heptanone, 5-methyl-2-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone, 2-octanone, 3-octanone, 4-octanone, cyclohexanone, 2,6-dimethylcyclohexanone, 2-acetylcyclohexanone, menthone, cyclopentanone, and dicyclohexyl ketone; aliphatic diketones such as 2,5-hexanedione, 2,4-pentanedione, and acetylacetone; and aromatic ketones such as acetophenone, 1-phenylethanone, and benzophenone. Among these, the iodine scavenger is preferably an aliphatic ketone, more preferably 4-methyl-2-pentanone, 5-methyl-3-pentanone, 2,4-dimethyl-3-pentanone, or cyclohexanone, and even more preferably 4-methyl-2-pentanone. These iodine scavenger agents may be used alone or in combination of two or more.

[0089] [Low-Dielectric-Constant Passivator] The etching composition for a semiconductor substrate for a memory element may further contain a low-dielectric-constant passivator, which has the function of preventing or suppressing etching of a low-dielectric-constant film, such as an insulating film.

[0090] The low dielectric constant passivator is not particularly limited, but examples thereof include boric acid; borates such as ammonium pentaborate and sodium tetraborate; and carboxylic acids such as 3-hydroxy-2-naphthoic acid, malonic acid, and iminodiacetic acid.

[0091] These low dielectric constant passivators may be used alone or in combination of two or more.

[0092] The addition rate of the low dielectric constant passivator is preferably 0.01 to 2 mass %, more preferably 0.02 to 1 mass %, and even more preferably 0.03 to 0.5 mass %, based on the total mass of the etching composition for semiconductor substrates for memory elements.

[0093] [Additives] The etching composition for a semiconductor substrate for a memory element may further contain additives, such as surfactants, chelating agents, antifoaming agents, and silicon-containing compounds.

[0094] [Physical Properties] The surface tension of the etching composition for memory element semiconductor substrates is preferably 50 mN / m or less, more preferably 40 mN / m or less, even more preferably 10 to 35 mN / m, particularly preferably 20 to 32 mN / m, and most preferably 25 to 30 mN / m. When the surface tension of the etching composition for memory element semiconductor substrates is 50 mN / m or less, the metal tungsten anticorrosive agent can easily penetrate into minute spaces on the side of the metal tungsten film that arise as selective etching of a titanium-containing film (barrier film) containing titanium or a titanium alloy progresses, thereby favorably preventing or suppressing etching (corrosion) from the side of the metal tungsten. In this specification, the surface tension is measured by the method described in the Examples. The surface tension of the etching composition for memory element semiconductor substrates can be adjusted, for example, by using a metal tungsten anticorrosive agent (C) with a larger carbon number or by adding a more hydrophobic organic solvent (E).

[0095] The pH of the etching composition for semiconductor substrates for memory devices is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, even more preferably 0.8 to 1.5, and particularly preferably 0.8 to 1.3. The pH of the etching composition for semiconductor substrates for memory devices within the above range is preferred because it can reduce the amount of etching (corrosion) of metallic tungsten. In this specification, the pH is measured by the method described in the Examples. The pH of the etching composition for semiconductor substrates for memory devices can be adjusted, for example, by adding a pH adjuster (D).

[0096] <Method for manufacturing a semiconductor substrate for a memory device> According to one aspect of the present invention, there is provided a method for manufacturing a semiconductor substrate for a memory device, which includes the step of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy and a metallic tungsten film with the etching composition for the semiconductor substrate for a memory device described above to remove at least a portion of the titanium-containing film.

[0097] [Semiconductor Substrate] The semiconductor substrate has a titanium-containing film containing at least one of titanium and a titanium alloy, and a metal tungsten film. The configuration of the semiconductor substrate is not particularly limited, and a known configuration can be appropriately adopted.

[0098] For example, when used in a buried word line of a memory device, the semiconductor substrate may have a structure in which an insulating film, a barrier film made of titanium and / or a titanium alloy, and a metallic tungsten film are stacked in this order on a silicon substrate having a recess, with the barrier film and the metallic tungsten film usually being adjacent to each other.

[0099] [Etching composition for semiconductor substrate for memory element] As the etching composition for semiconductor substrate for memory element, the above-mentioned compounds are used.

[0100] [Contact] The method of contacting the semiconductor substrate with the etching composition for memory element semiconductor substrates is not particularly limited, and known techniques can be appropriately adopted. Specifically, the semiconductor substrate may be immersed in the etching composition for memory element semiconductor substrates, or the etching composition for memory element semiconductor substrates may be sprayed or dripped onto the semiconductor substrate (single wafer spin treatment, etc.). In this case, the immersion may be repeated two or more times, the spraying may be repeated two or more times, the dripping may be repeated two or more times, or immersion, spraying, and dripping may be combined.

[0101] The contact temperature is not particularly limited, but is preferably 0 to 90°C, more preferably 15 to 70°C, and even more preferably 20 to 60°C.

[0102] The contact time is not particularly limited, but is preferably from 10 seconds to 3 hours, more preferably from 30 seconds to 1 hour, even more preferably from 1 to 45 minutes, and particularly preferably from 1 to 5 minutes.

[0103] By contacting the semiconductor substrate with the etching composition for semiconductor substrates for memory devices, selective etching of titanium and titanium alloys can be performed.

[0104] (Semiconductor substrate for memory device) The obtained semiconductor substrate for memory device can be used for memory devices such as DRAM, etc. The memory device can be made smaller and more highly functional.

[0105] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0106] [Example 1] (A) Iodic acid (HIO) as an oxidizing agent ３ (B) hydrogen fluoride (HF), a fluorine compound; and (C) benzethonium chloride (BZT), a metal tungsten (W) corrosion inhibitor, were added to pure water and stirred to produce an etching composition for memory element semiconductor substrates. The addition rates of iodic acid, hydrogen fluoride, and benzethonium chloride (BZT) were 0.018 mass%, 0.05 mass%, and 0.02 mass%, respectively, relative to the total mass of the etching composition for memory element semiconductor substrates. The pH and surface tension of the etching composition for memory element semiconductor substrates were 2.4 and 38 mN / m, respectively. The pH of the etching composition for memory element semiconductor substrates was measured at 23°C using a benchtop pH meter (F-71) and a pH electrode (9615S-10D) manufactured by Horiba, Ltd. The surface tension of the etching composition for the semiconductor substrate for memory elements was measured at 23° C. using an automatic surface tensiometer DY-300 (manufactured by Kyowa Interface Science Co., Ltd.).

[0107] [Examples 2 to 17 and Comparative Example 1] Etching compositions for semiconductor substrates for memory elements were produced by changing the components to be added as shown in the following Table 1. The pH and surface tension were measured in the same manner as in Example 1.

[0108]

[0109] The structures of BZT, BOctDAC, BZC, HexDMIC, OctDMIC, HexDPC, BTetDAC, and DPC, which are the metal tungsten corrosion inhibitors (C) used in Examples 1 to 17 and Comparative Example 1, are shown below.

[0110]

[0111] [Evaluation] The etching compositions for the semiconductor substrates for memory elements produced in Examples 1 to 17 and Comparative Example 1 were evaluated for the amount of corrosion of a metal tungsten film, the amount of etching of a titanium nitride film, the etching selectivity (TiN / W etching selectivity) which is the ratio of the amount of etching of a titanium nitride film to the amount of corrosion of a metal tungsten film, and the etching rate of a thermal oxide film (th-Ox) made of silicon dioxide.

[0112] (Preparation of Evaluation Samples) A ​​thermally oxidized film (100 nm) made of silicon dioxide was formed on a silicon substrate. A titanium nitride film (5 nm), a metallic tungsten film (50 nm), and a silicon dioxide film (50 nm) were sequentially formed on the surface of this thermally oxidized film by CVD (chemical vapor deposition) to prepare a wafer.

[0113] A trench (groove) was formed on the fabricated wafer from the silicon dioxide film formed by CVD to the thermal oxide film made of silicon dioxide on the silicon substrate surface to prepare an evaluation sample (before etching). Specifically, the fabricated wafer was cut into 1 cm × 1 cm pieces, and a carbon protective film was formed in the trench formation area using a focused ion beam (FIB) device (Helios G4 UX, manufactured by Thermo Scientific). Next, a trench (groove) was formed in the wafer from the surface of the carbon protective film using the FIB. The resulting trench-processed body was treated with a dilute hydrofluoric acid solution (prepared by diluting 50% hydrogen fluoride with water 1000 times (volume ratio)) at 70 °C for 5 minutes to prepare an evaluation sample (before etching).

[0114] A schematic diagram of the fabricated evaluation sample (before etching) is shown in FIG. The evaluation sample (before etching) 40 includes a silicon substrate 41 and a thermally oxidized silicon dioxide film 42 (100 nm), a titanium nitride film 43 (5 nm), a metal tungsten film 44 (50 nm), a silicon dioxide film 45 (50 nm), and a carbon protective film 46, in this order. A trench was formed by FIB from the silicon dioxide film 45 to the thermally oxidized silicon dioxide film 42, with the carbon protective film 46 interposed therebetween. The formed trench had a trapezoidal shape, with a width of 40 nm at the interface between the silicon dioxide film 45 and the metal tungsten film 44, and a width of 20 nm at the interface between the titanium nitride film 43 and the thermally oxidized silicon dioxide film 42.

[0115] (Etching Treatment) The evaluation sample (before etching) was immersed in an etching composition for semiconductor substrates for memory elements and allowed to stand for 30 minutes at 50° C. The evaluation sample was removed from the etching composition for semiconductor substrates for memory elements and subjected to FIB processing to obtain an evaluation sample (after etching) having a smooth cross section.

[0116] (Amount of Corrosion of Metal Tungsten Film) A TEM image of the evaluation sample (after etching) was obtained using Helios G4 UX (manufactured by Thermo Scientific).

[0117] 3 is a schematic diagram of the evaluation sample (after etching). In the evaluation sample (after etching), the titanium nitride film 53 is etched. Furthermore, the metal tungsten film 54 can be etched (corroded).

[0118] The amount of corrosion of the metallic tungsten film was calculated using Image J (image processing software developed by Wayne Rasband of the National Institutes of Health) for the TEM image obtained above. Specifically, the corroded area 57 of the metallic tungsten film in FIG. 3 was quantified (unit: nm ２ The results are shown in Table 2 below.

[0119] (Etching Amount of Titanium Nitride Film) The etching amount of the titanium nitride film was calculated using Image J (image processing software developed by Wayne Rasband of the National Institutes of Health) for the TEM images obtained in calculating the corrosion amount of the metal tungsten film. Specifically, the etching depth 58 of the titanium nitride film in FIG. 3 was quantified (unit: nm). The etching amount of the titanium nitride film was calculated (unit: nm) by multiplying the etching depth of the titanium nitride film (unit: nm) by the contact area of ​​the titanium nitride film with the etching composition of the semiconductor substrate for memory devices (5 nm: see FIG. 2). ２ The results are shown in Table 2 below.

[0120] (Calculation of TiN / W etching selectivity) Etching amount of titanium nitride film (nm ２ ) is the corrosion amount of the metal tungsten film (nm ２ The TiN / W etching selectivity was calculated by dividing the result by the value of the etching selectivity of TiN / W. The results are shown in Table 2 below.

[0121] (Etching Rate of Thermal Oxide Film (th-Ox) Made of Silicon Dioxide) Using an optical film thickness meter n&k1280 (manufactured by n&k Technology), the film thickness of the thermal oxide film (th-Ox) made of silicon dioxide of the evaluation sample (before etching) and the film thickness of the thermal oxide film (th-Ox) made of silicon dioxide of the evaluation sample (after etching) were measured. The etching rate of the thermal oxide film (th-Ox) made of silicon dioxide was calculated by dividing the difference in film thickness before and after the etching process by the treatment time (30 minutes). The obtained results are shown in Table 2 below.

[0122]

[0123] The results in Table 2 show that the etching compositions for semiconductor substrates for memory devices in Examples 1 to 17 caused less corrosion of the metal tungsten film, and as a result, the resulting semiconductor substrates for memory devices are believed to exhibit improved performance.

[0124] REFERENCE SIGNS LIST 10 Semiconductor substrate (before etching) 11, 21, 31 Silicon substrate having recess 12, 22, 32 Insulating film 13 Barrier film (before etching) 14 Metallic tungsten film 20, 30 Semiconductor substrate (after etching) 23, 33 Barrier film (after etching) 24, 34 Metallic tungsten film 24a Metallic tungsten film surface 24b Metallic tungsten film side surface 34c Corroded surface of metal tungsten film 40 Evaluation sample (before etching) 41 Silicon substrate 42 Thermal oxide film made of silicon dioxide 43 Titanium nitride film (before etching) 44 Metallic tungsten film 45 Silicon dioxide film 46 Carbon protective film 52 Thermal oxide film made of silicon dioxide 53 Titanium nitride film (after etching) 54 Metallic tungsten film 55 Silicon dioxide film 57 Corroded area of ​​metal tungsten film 58 Etching depth of titanium nitride film

Claims

1. An etching composition for a semiconductor substrate for a memory element, comprising: (A) an oxidizing agent; (B) a fluorine compound; and (C) a metal tungsten corrosion inhibitor, The (C) metallic tungsten corrosion inhibitor is represented by the following formula (1): 【Chemistry 1】 (In the above formula (1), R １ is a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms, a substituted or unsubstituted alkyl (poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl (poly)heteroalkylene group having 14 to 30 carbon atoms, R ２ each independently represents a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms; X - is a halide ion, a hydroxide ion, an organic sulfonate ion, a tetrafluoroborate anion, or a hexafluorophosphate anion. and a heteroaryl salt having a substituted or unsubstituted alkyl group having 14 to 30 carbon atoms.

2. The R １ The etching composition for semiconductor substrates for memory elements according to claim 1, wherein is a substituted or unsubstituted alkyl (poly)heteroalkylene group having 14 to 30 carbon atoms, or a substituted or unsubstituted aryl (poly)heteroalkylene group having 14 to 30 carbon atoms.

3. The R １ 3. The etching composition for a semiconductor substrate for a memory element according to claim 2, wherein is a substituted or unsubstituted aryl (poly)heteroalkylene group having 14 to 20 carbon atoms.

4. 2. The etching composition for a semiconductor substrate for a memory element according to claim 1, wherein the etching composition has a surface tension of 50 mN / m or less.

5. The etching composition for a semiconductor substrate for a memory element according to claim 1 , further comprising (D) a pH adjuster.

6. 2. The etching composition for a semiconductor substrate for a memory element according to claim 1, wherein the pH is 0.1 to 5.

0.

7. The etching composition for a semiconductor substrate for a memory element according to claim 1 , further comprising: (E) an organic solvent.

8. 8. The etching composition for a semiconductor substrate for a memory element according to claim 7, wherein the organic solvent (E) is an alcohol.

9. A method for producing a semiconductor substrate for a memory element, comprising the step of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy and a metal tungsten film with the etching composition for a semiconductor substrate for a memory element according to any one of claims 1 to 8, thereby removing at least a part of the titanium-containing film.

Images