Method for manufacturing semiconductor substrate for memory device

Abstract

The present invention provides a method for producing a semiconductor substrate for highly functional memory elements with high production efficiency.　A method for producing a semiconductor substrate for memory elements, the method comprising: a step (1) in which a semiconductor substrate that has a titanium-containing film that contains at least one of titanium and a titanium alloy, a tungsten metal film, and a tungsten oxide film is brought into contact with a pretreatment agent, thereby removing at least a part of the tungsten oxide film; and a step (2) in which the semiconductor substrate after the step (1) is brought into contact with an etching agent, thereby removing at least a part of the titanium-containing film. With respect to this method for producing a semiconductor substrate for memory elements, the pretreatment agent contains at least one tungsten oxide etchant that is selected from the group consisting of acids, ammonia, and ammonium salts.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a semiconductor substrate for a memory device. [Background technology]

[0002] In recent years, there has been an increasing demand for smaller and more functional 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 chemical vapor deposition (CVD) 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 DRAM.

[0004] It is known that the buried word line can be manufactured, for example, by the following method. That is, a silicon oxide film, a titanium-containing film (barrier film) containing titanium or a titanium alloy, and a metallic tungsten film are sequentially formed on a silicon substrate having a recess formed by etching. Next, the surface is 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). Thereafter, the titanium-containing film is selectively etched to manufacture the buried word line of the memory element (Non-Patent Document 1).

[0005] Thus, the manufacturing method for semiconductor substrates for memory devices includes a step of selectively removing titanium and titanium alloys without damaging metallic tungsten (selective etching step for titanium and titanium alloys). Therefore, when manufacturing small, high-performance memory devices using metallic tungsten, an etching agent that etches titanium and titanium alloys (with a high Ti / W etching selectivity) without etching metallic tungsten is required. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] 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] Summary of the Invention [Problem to be solved by the invention]

[0007] However, it has been found that even when semiconductor substrates for memory devices using metallic tungsten are manufactured using conventional etching agents, memory devices with the desired performance may not be obtained. One possible reason for this is the influence of a tungsten oxide film formed by oxidation of the surface of the metallic tungsten film during the manufacturing process of the semiconductor substrate for memory devices. For example, in buried word lines, if a tungsten oxide film exists covering at least a portion of the surface of a titanium-containing film, the etching agent may not be able to contact the titanium or titanium alloy, making it impossible to etch the titanium or titanium alloy.

[0008] Therefore, it is possible to remove tungsten oxide using a pretreatment agent before the selective etching process of titanium nitride using an etching agent. In this case, if the pretreatment agent's tungsten oxide film removal rate is slow, the pretreatment process using the pretreatment agent will take longer, reducing the production efficiency (throughput) of semiconductor substrates for memory devices. Therefore, it is preferable to use a pretreatment agent with a high tungsten oxide removal rate. Using such a pretreatment agent allows for rapid removal of the tungsten oxide film, and then the selective etching process of titanium and titanium alloys using an etching agent can be performed, resulting in the production of high-performance semiconductor substrates for memory devices with high production efficiency.

[0009] That is, the present invention provides a method for manufacturing a semiconductor substrate for a high-performance memory device with high production efficiency. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems. As a result, they have discovered that the above problems can be solved by removing the tungsten oxide film using a specific pretreatment agent before the selective etching process of titanium and titanium alloys using an etching agent, and have completed the present invention. That is, the present invention is, for example, as follows.

[0011] [1] A step (1) of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film with a pretreatment agent to remove at least a portion of the tungsten oxide film; (2) contacting the semiconductor substrate after step (1) with an etching agent to remove at least a portion of the titanium-containing film; Including, The method for manufacturing a semiconductor substrate for a memory element, wherein the pretreatment agent contains at least one tungsten oxide etchant selected from the group consisting of acid, ammonia, and ammonium salt. [2] The method according to the above [1], wherein the pH of the pretreatment agent is 0.1 to 13. [3] The manufacturing method according to [1] or [2] above, wherein the tungsten oxide etchant comprises at least one selected from the group consisting of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, and phosphoric acid. [4] The semiconductor substrate further includes a titanium oxide film; The manufacturing method according to any one of the above [1] to [3], wherein the step (1) further comprises removing at least a portion of the titanium oxide film. [5] The etching agent comprises (A) an oxidizing agent, (B) a fluorine compound, and (C) a metal tungsten corrosion inhibitor; the addition rate of the (A) oxidizing agent is 0.0001 to 10 mass% relative to the total mass of the etching agent, the content of the (B) fluorine compound is 0.005 to 10 mass% relative to the total mass of the etching agent, The manufacturing method according to any one of the above [1] to [4], wherein the content of the (C) metal tungsten corrosion inhibitor is 0.0001 to 5 mass % relative to the total mass of the etching agent. [6] The method according to [5] above, wherein the (A) oxidizing agent comprises at least one selected from the group consisting of peracids, halogen oxoacids, and salts thereof. [7] The manufacturing method according to [5] or [6] above, wherein the (B) fluorine compound comprises at least one selected from the group consisting of hydrogen fluoride (HF), tetrafluoroboric acid (HBF4), hexafluorosilicic acid (H2SiF6), hexafluorozirconic acid (H2ZrF6), hexafluorotitanic acid (H2TiF6), hexafluorophosphoric acid (HPF6), hexafluoroaluminic acid (H2AlF6), hexafluorogermanic acid (H2GeF6), and salts thereof. [8] The (C) metal tungsten corrosion inhibitor is represented by the following formula (1): [ka] (In the above formula (1), R 1represents an alkyl group having 5 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group, a substituted or unsubstituted aryl(poly)heteroalkylene group, a group represented by the following formula (2): [ka] (In the above formula, Cy is a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 2 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 15 carbon atoms; Each A is independently an alkylene having 1 to 5 carbon atoms, r is 0 or 1, Z is represented by the following formula: [ka] ) is a group represented by R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, X is a halide ion, a hydroxide ion, an organic sulfonate ion, tetrafluoroborate, or hexafluorophosphate. and heteroaryl salts having an alkyl group having 5 to 30 carbon atoms. [Effects of the Invention]

[0012] According to the present invention, a method for manufacturing a semiconductor substrate for a high-performance memory element with high production efficiency is provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of step (1) according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] <Method of manufacturing semiconductor substrate for memory element> The method for manufacturing a semiconductor substrate for a memory element according to the present invention includes the steps of: (1) contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film with a pretreatment agent to remove at least a portion of the tungsten oxide film; and (2) contacting the semiconductor substrate after step (1) with an etching agent to remove at least a portion of the titanium-containing film, wherein the pretreatment agent contains at least one tungsten oxide etchant selected from the group consisting of acid, ammonia, and ammonium salt.

[0016] The pretreatment agent has a high etching rate for tungsten oxide formed on the surface of a tungsten-containing material in a semiconductor substrate, and can effectively remove tungsten oxide, thereby preventing a decrease in throughput. Furthermore, the etching rate for tungsten metal during pretreatment is sufficiently slow, allowing for the production of high-performance semiconductor substrates for memory devices with high production efficiency.

[0017] The titanium alloy is not particularly limited as long as it is titanium to which one or more metal or nonmetal elements other than titanium have been added and has metallic properties. Examples include alloys of titanium and at least one element selected from the group consisting of aluminum, nitrogen, carbon, molybdenum, vanadium, niobium, iron, chromium, nickel, tin, hafnium, zirconium, palladium, ruthenium, and platinum. Among these, titanium nitride is preferred. In this specification, the term "titanium alloy" refers to a titanium alloy containing 20 atomic percent or more of titanium, based on the total atomic weight of the titanium alloy. The titanium content in the titanium alloy is preferably 20 atomic percent or more, more preferably 30 atomic percent, even more preferably 35 atomic percent, and particularly preferably 40 to 99.9 atomic percent, based on the total atomic weight of the titanium alloy.

[0018] In addition, in this specification, "tungsten oxide" refers to a substance formed by oxidizing metallic tungsten, and generally means tungsten (VI) oxide (WO3).

[0019] The present invention will be described below with reference to the drawings. Note that the drawings may be exaggerated for the purpose of explanation and may differ from the actual dimensions.

[0020] FIG. 1 is a schematic diagram of step (1) according to the present invention. A semiconductor substrate (before step (1)) 10 includes a silicon substrate 11 having a recess, an insulating film 12 made of silicon oxide, a barrier film 13 made of titanium nitride, and a metallic tungsten film 14. This semiconductor substrate (before step (1)) 10 can be manufactured by sequentially depositing an insulating film made of silicon oxide, a barrier film made of titanium nitride, and a metallic tungsten film on a silicon substrate having a recess, followed by planarization by chemical mechanical polishing (CMP) and selective etching of the barrier film and the metallic tungsten film by dry etching or the like (CMP may be omitted). Here, the semiconductor substrate (before cleaning) 10 includes a tungsten oxide film 15 formed by oxidation of the metallic tungsten on the barrier film 13 and the metallic tungsten film 14. Because the tungsten oxide film 15 covers the surface of the barrier film 13, selective etching of the titanium nitride barrier film 13 may prevent the etchant from properly contacting the barrier film 13, making it impossible to etch the barrier film 13. 1, a titanium oxide film 16 is formed on the surface of a barrier film 13 made of titanium nitride. The titanium oxide film 16 can be formed by oxygen passing through the tungsten oxide film 15 due to the low film density of the tungsten oxide film 15 and oxidizing the titanium nitride on the surface of the barrier film 13. Alternatively, the titanium oxide film 16 can be formed by oxidizing titanium nitride in an ashing process that is optionally performed in the manufacturing process of a semiconductor substrate for a memory device.

[0021] By applying a pretreatment agent to a semiconductor substrate (before cleaning) 10 having such a configuration, the tungsten oxide film 15 can be removed. Since the pretreatment agent has a high etching rate for tungsten oxide, high production efficiency can be achieved without reducing throughput. Furthermore, etching of metallic tungsten during pretreatment can be prevented or suppressed. As a result, the semiconductor substrate (after step (1)) 20 obtained by pretreatment has a structure in which a silicon substrate 21 having a recess, an insulating film 22 made of silicon oxide, a barrier film 23 made of titanium nitride, and a metallic tungsten film 24 are stacked. Therefore, when an etching agent is applied in step (2), the etching agent can be favorably contacted with the barrier film 23. As a result, titanium nitride can be selectively etched, and the resulting semiconductor substrate (after step (2)) 30 has a structure in which a silicon substrate 31 having a recess, an insulating film 32, an etched barrier film 33, and a metallic tungsten film 34 are stacked.

[0022] In a preferred embodiment, the pretreatment agent does not or barely causes galvanic corrosion (galvanic corrosion). When titanium or titanium alloys come into contact with metallic tungsten, depending on the processing environment, galvanic corrosion is more likely to occur in metallic tungsten, which has a relatively low natural potential compared to titanium or titanium alloys. However, in a preferred embodiment of the present invention, galvanic corrosion can be prevented or suppressed by using a suitable pretreatment agent.

[0023] In a preferred embodiment, the pretreatment agent can remove at least a portion of the titanium oxide film 16 along with the tungsten oxide film 15. This allows the etching agent to more effectively contact the titanium or titanium alloy. As a result, the titanium or titanium alloy can be more selectively etched, resulting in the production of a high-performance semiconductor substrate.

[0024] Each step will be described in detail below.

[0025] [Process (1)] Step (1) is a step of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film with a pretreatment agent to remove at least a portion of the tungsten oxide film.

[0026] (semiconductor substrate) The semiconductor substrate includes a titanium-containing film containing at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film. The configuration of the semiconductor substrate is not particularly limited, and a known configuration can be appropriately adopted.

[0027] 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.

[0028] The semiconductor substrate further includes a tungsten oxide film formed by oxidation of the tungsten metal on the surface of the tungsten metal film. The shape of the tungsten oxide film is not particularly limited. For example, the tungsten oxide film may be formed to have a uniform thickness or a non-uniform thickness. The tungsten oxide film may be formed as a single continuous film or as a plurality of discontinuous films. Since the volume of tungsten oxide increases as the tungsten metal oxidizes, the tungsten oxide film may be present on the surface of a film adjacent to the tungsten metal film, such as a barrier film. The tungsten oxide film is preferably removed by a pretreatment agent in step (1).

[0029] The semiconductor substrate may further include a titanium oxide film formed by oxidation of titanium or a titanium alloy on the surface of the titanium-containing film. The titanium oxide film may be formed by natural oxidation of the titanium or titanium alloy on the surface of the titanium-containing film. Even if the surface of the titanium-containing film is covered with a tungsten oxide film, natural oxidation of the surface of the titanium-containing film may occur if the tungsten oxide film has a low film density because oxygen can pass through the tungsten oxide film. The titanium oxide film may also be formed by oxidation of titanium or a titanium alloy during an ashing step, which is optionally performed in the manufacturing process of a semiconductor substrate for memory devices. The shape of the titanium oxide film is not particularly limited. For example, the titanium oxide film may be formed with a uniform thickness or a non-uniform thickness. It may also be a single continuous film or a plurality of discontinuous films. The titanium oxide film is preferably removed by a pretreatment agent in step (1). That is, in a preferred embodiment, the semiconductor substrate further includes a titanium oxide film, and step (1) preferably further includes removing at least a portion of the titanium oxide film. In this specification, "titanium oxide" refers to a substance formed by oxidizing titanium nitride, and is usually titanium oxide (IV) (TiO2), titanium oxynitride (TiO x N y ) (wherein x is 0.01 to 2 and y is 0 to 1), and combinations thereof.

[0030] (Pretreatment agent) The pretreatment agent contains a tungsten oxide etchant. By using the pretreatment agent, at least a portion of the tungsten oxide film can be removed. Therefore, the pretreatment agent can be said to be a treatment agent for removing a tungsten oxide film.

[0031] Tungsten Oxide Etchant The tungsten oxide etchant includes at least one selected from the group consisting of an acid, ammonia, and an ammonium salt.

[0032] The acid is not particularly limited, but examples thereof include inorganic acids such as hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, and phosphoric acid; and organic acids such as acetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 10-camphorsulfonic acid.

[0033] The ammonium salt is not particularly limited, but examples thereof include ammonium fluoride (NHF); ammonium hydrogen fluoride (NHF·HF); tetraalkylammonium hydroxides such as tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMAH), ethyltrimethylammonium hydroxide, diethyldimethylammonium hydroxide, triethylmethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; aryl group-containing ammonium hydroxides such as benzyltrimethylammonium hydroxide and benzyltriethylammonium hydroxide; and hydroxy group-containing ammonium hydroxides such as trimethyl(2-hydroxyethyl)ammonium hydroxide, triethyl(2-hydroxyethyl)ammonium hydroxide, tripropyl(2-hydroxyethyl)ammonium hydroxide, and trimethyl(1-hydroxypropyl)ammonium hydroxide.

[0034] Of the above, the tungsten oxide etchant is preferably an acid, ammonium fluoride, or ammonium hydrogen fluoride from the viewpoint of preventing or suppressing galvanic corrosion, more preferably an inorganic acid, still more preferably hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, or phosphoric acid, particularly preferably hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, or nitric acid, and most preferably hydrogen fluoride from the viewpoint of suitably removing titanium oxide.

[0035] The above-mentioned tungsten oxide etchants may be used alone or in combination of two or more. That is, in one embodiment, from the viewpoint of preventing or suppressing galvanic corrosion, the tungsten oxide etchant preferably contains at least one selected from the group consisting of acid, ammonium fluoride, and ammonium hydrogen fluoride, more preferably contains at least one inorganic acid, further preferably contains at least one selected from the group consisting of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, and phosphoric acid, particularly preferably contains at least one selected from the group consisting of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, and nitric acid, and most preferably contains hydrogen fluoride from the viewpoint of being able to suitably remove titanium oxide.

[0036] The content of the tungsten oxide etchant is preferably 0.001 to 50 mass% relative to the total mass of the pretreatment agent, more preferably 0.01 to 10 mass%, even more preferably 0.03 to 3 mass%, and particularly preferably 0.05 to 1 mass%. A tungsten oxide etchant content of 0.001 mass% or more is preferred because it increases the etching rate of tungsten oxide. On the other hand, a tungsten oxide etchant content of 50 mass% or less is preferred because it can prevent or suppress etching of metallic tungsten in step (1).

[0037] solvent The pretreatment agent preferably contains a solvent, which has the functions of uniformly dispersing the components contained in the pretreatment agent, diluting the pretreatment agent, and the like.

[0038] The solvent includes water and organic solvents.

[0039] 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.

[0040] The organic solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and tert-butanol; polyhydric alcohols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethylhexane-1,3-diol, and glycerin; and glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl 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.

[0041] Of the above, the solvent is more preferably water. The solvents may be used alone or in combination of two or more.

[0042] The content of the solvent, particularly water, relative to the total mass of the pretreatment agent is preferably 50 mass% or more, more preferably 80 mass% or more, even more preferably 90 mass% or more, and particularly preferably 95 mass% or more.

[0043] additives The pretreatment agent may further contain an additive. Examples of the additive include, but are not limited to, pH adjusters such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. These additives may be used alone or in combination of two or more.

[0044] Pretreatment agent properties The pH of the pretreatment agent is preferably 0.1 to 13, and from the viewpoint of preventing or suppressing galvanic corrosion, it is more preferably 0.5 to 10, even more preferably 0.5 to 5, and particularly preferably 0.4 to 2.5.

[0045] The etching rate of the tungsten oxide in the pretreatment agent is preferably 15 Å / min or higher, more preferably 20 to 500 Å / min, even more preferably 20 to 100 Å / min, and particularly preferably 20 to 50 Å / min. An etching rate of the tungsten oxide in the pretreatment agent of 15 Å / min or higher is preferable because it prevents a decrease in throughput and can prevent etching of metallic tungsten during pretreatment. The etching rate of the tungsten oxide in the pretreatment agent refers to a value measured by the method in the Examples.

[0046] The etching rate of the tungsten metal in the pretreatment agent is preferably 10 Å / min or less, more preferably 7.5 Å / min or less, even more preferably 5.0 Å / min or less, particularly preferably 3.0 Å / min or less, and most preferably 0.1 to 2.8 Å / min. A pretreatment agent having an etching rate of 10 Å / min or less is preferred because etching of the tungsten metal in step (1) (pretreatment) can be prevented. The etching rate of the tungsten metal in the pretreatment agent refers to a value measured by the method in the Examples.

[0047] The etching rate of titanium and titanium alloys in the pretreatment agent is preferably 10 Å / min or less, more preferably 6 Å / min or less, and even more preferably 2 Å / min or less. A pretreatment agent with an etching rate of 10 Å / min or less is preferred because etching in step (2) described below can be carried out efficiently. The etching rate of titanium and titanium alloys in the pretreatment agent refers to a value measured by the method in the Examples.

[0048] The etching rate of the insulating layer material of the pretreatment agent is preferably 3.0 Å / min or less, more preferably 1.0 Å / min or less, even more preferably 0.3 Å / min or less, particularly preferably 0.2 Å / min or less, and most preferably 0.1 Å / min or less. An etching rate of the insulating layer material of the pretreatment agent of 3.0 Å / min or less is preferable because it maintains the shape of the semiconductor substrate and improves the performance of the semiconductor device. The insulating layer material is not particularly limited, but examples include silicon oxide (e.g., th-Ox). The etching rate of the insulating layer material of the pretreatment agent refers to a value measured by the method in the Examples.

[0049] The WO3 / W etching selectivity of the pretreatment agent is preferably 5 or greater, more preferably 10 to 100, even more preferably 15 to 100, particularly preferably 30 to 100, and most preferably 50 to 90. A WO3 / W etching selectivity of 5 or greater is preferable because it allows for the production of high-performance semiconductor substrates for memory elements. In this specification, the term "WO3 / W etching selectivity" refers to the etching selectivity between tungsten oxide and metallic tungsten, and more specifically, refers to the ratio of the etching rate of tungsten oxide to the etching rate of metallic tungsten (etching rate of tungsten oxide / etching rate of metallic tungsten).

[0050] The corrosion potential of the metallic tungsten (W) in the pretreatment agent is preferably −1000 to −50 mV, more preferably −500 to −50 mV, even more preferably −300 to −50 mV, particularly preferably −150 to −60 mV, and most preferably −115 to −70 mV. The corrosion potential of the metallic tungsten (W) in the pretreatment agent is a value measured by the method in the examples.

[0051] The corrosion potential of titanium and titanium alloys in the pretreatment agent is preferably −500 to −20 mV, more preferably −350 to −20 mV, even more preferably −200 to −20 mV, particularly preferably −130 to −30 mV, and most preferably −100 to −40 mV. The corrosion potential of titanium and titanium alloys in the pretreatment agent refers to a value measured by the method in the Examples.

[0052] The corrosion potential difference between metallic tungsten (W) and titanium / titanium alloy (corrosion potential difference of metallic tungsten (W) - corrosion potential of titanium / titanium alloy) in the pretreatment agent is not particularly limited, but is preferably -50 to 300 mV, more preferably -50 to 200 mV, even more preferably -30 to 100 mV, particularly preferably -30 to 50 mV, and most preferably -10 to 40 mV. A corrosion potential difference within the above range is preferable because it can prevent or suppress the occurrence of galvanic corrosion of metallic tungsten (W).

[0053] (contact) The method for contacting the semiconductor substrate with the pretreatment agent is not particularly limited, and known techniques can be appropriately adopted. Specifically, the semiconductor substrate may be immersed in the pretreatment agent, or the pretreatment agent may be sprayed or dripped onto the semiconductor substrate (e.g., single-wafer spin treatment). In this case, the immersion may be repeated two or more times, the spraying may be repeated two or more times, or the dripping may be repeated two or more times, or immersion, spraying, and dripping may be combined.

[0054] The contact temperature is not particularly limited, but is preferably 0 to 90°C, more preferably 15 to 80°C, and even more preferably 20 to 70°C.

[0055] The contact time is not particularly limited, but is preferably from 10 seconds to 3 hours, more preferably from 10 seconds to 1 hour, even more preferably from 10 seconds to 45 minutes, and particularly preferably from 20 seconds to 5 minutes.

[0056] By bringing the semiconductor substrate into contact with the pretreatment agent, at least a portion of the tungsten oxide film can be removed.

[0057] [Process (2)] Step (2) is a step of contacting the semiconductor substrate after step (1) with an etching agent to remove at least a portion of the titanium-containing film.

[0058] (Semiconductor substrate after step (1)) The semiconductor substrate after step (1) has a titanium-containing film and a metallic tungsten film. The tungsten oxide film is preferably completely removed in step (1), but a portion may remain. Furthermore, if the semiconductor substrate before step (1) contains a titanium oxide film, the titanium oxide film is preferably completely removed in step (1), but a portion or all of the film may remain. By performing step (1), at least a portion of the tungsten oxide film is removed from the semiconductor substrate after step (1), allowing the titanium-containing film to be favorably contacted with an etching agent in step (2), and thus allowing favorable selective etching of titanium and titanium alloys.

[0059] (etching agent) The etching agent is not particularly limited as long as it etches metallic tungsten slowly and etches titanium and titanium alloys (having a high Ti / W etching selectivity), and known etching agents can be used. Among these, the etching agent preferably contains (A) an oxidizing agent, (B) a fluorine compound, and (C) a metallic tungsten corrosion inhibitor. In this case, the addition rate of the oxidizing agent (A) is preferably 0.0001 to 10 mass% based on the total mass of the etching agent. Furthermore, the addition rate of the fluorine compound (B) is preferably 0.005 to 10 mass% based on the total mass of the etching agent. Furthermore, the addition rate of the metallic tungsten corrosion inhibitor (C) is preferably 0.0001 to 5 mass% based on the total mass of the etching agent. The preferred etching agents are described in detail below. In this specification, the term "Ti / W etching selectivity" refers to the etching selectivity between titanium and titanium alloys and metallic tungsten, and more specifically, refers to the ratio of the etching rate of titanium and titanium alloys to the etching rate of metallic tungsten (etching rate of titanium and titanium alloys / etching rate of metallic tungsten).

[0060] (A) Oxidizing agent (A) The oxidizing agent has a function of changing the oxidation number of titanium in titanium and titanium alloys to tetravalent, thereby dissolving the titanium in the etching agent.

[0061] (A) The oxidizing agent is not particularly limited, but includes peracids, halogen oxoacids, and salts thereof.

[0062] Examples of the peracid include hydrogen peroxide, persulfuric acid, percarbonic acid, perphosphoric acid, peracetic acid, perbenzoic acid, and metachloroperbenzoic acid.

[0063] 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.

[0064] 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.

[0065] The oxidizing agent (A) is preferably hydrogen peroxide or an oxoacid of iodine, more preferably hydrogen peroxide, iodic acid, or periodic acid, and further preferably hydrogen peroxide or periodic acid, since this increases the Ti / W etching selectivity, and particularly preferably periodic acid.

[0066] 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, still more 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 hydrogen peroxide and periodic acid, and most preferably contains periodic acid.

[0067] The addition rate of the (A) oxidizing agent 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 agent.

[0068] (B) Fluorine compounds (B) Fluorine compounds have the function of accelerating the etching of titanium and titanium alloys.

[0069] The (B) fluorine compound is not particularly limited, but examples thereof include hydrogen fluoride (HF), tetrafluoroboric acid (HBF), hexafluorosilicic acid (HSiF), hexafluorozirconic acid (HZrF), hexafluorotitanic acid (HTiF), hexafluorophosphoric acid (HPF), hexafluoroaluminic acid (HAlF), hexafluorogermanic acid (HGeF), and salts thereof.

[0070] In this case, examples of the salt include ammonium salts such as ammonium fluoride (NH4F), ammonium hydrogen fluoride (NH4F·HF), ammonium tetrafluoroborate (NH4BF4), ammonium hexafluorosilicate ((NH4)2SiF6), and tetramethylammonium tetrafluoroborate (N(CH3)4BF4).

[0071] Of the above, (B) the fluorine compound is preferably hydrogen fluoride (HF), tetrafluoroboric acid (HBF), hexafluorosilicic acid (H2SiF6), or a salt thereof, more preferably hydrogen fluoride (HF), ammonium fluoride (NH4F), ammonium hydrogen fluoride (NH4F·HF), or hexafluorosilicic acid (H2SiF6), and from the viewpoint of a high etching rate for titanium and titanium alloys, hydrogen fluoride (HF) or ammonium hydrogen fluoride (NH4F·HF) is even more preferable, with ammonium hydrogen fluoride (NH4F·HF) being particularly preferable.

[0072] The above-mentioned (B) fluorine compound may be used alone or in combination of two or more. That is, in a preferred embodiment, the (B) fluorine compound preferably includes at least one selected from the group consisting of hydrogen fluoride (HF), tetrafluoroboric acid (HBF4), hexafluorosilicic acid (H2SiF6), hexafluorozirconic acid (H2ZrF6), hexafluorotitanic acid (H2TiF6), hexafluorophosphoric acid (HPF6), hexafluoroaluminic acid (H2AlF6), hexafluorogermanic acid (H2GeF6), and salts thereof. It is more preferable that the solvent contains at least one selected from the group consisting of silicic acid (H2SiF6) and salts thereof, and even more preferable that the solvent contains at least one selected from the group consisting of hydrogen fluoride (HF), ammonium fluoride (NH4F), ammonium hydrogen fluoride (NH4F HF), and hexafluorosilicic acid (H2SiF6), and it is particularly preferable that the solvent contains at least one selected from the group consisting of hydrogen fluoride (HF) and ammonium hydrogen fluoride (NH4F HF), and it is most preferable that the solvent contains ammonium hydrogen fluoride (NH4F HF).

[0073] The addition rate of (B) the fluorine compound is preferably 0.005 to 10 mass %, more preferably 0.01 to 5 mass %, even more preferably 0.01 to 3 mass %, and particularly preferably 0.03 to 1 mass %, relative to the total mass of the etching agent.

[0074] (C) Metallic tungsten corrosion inhibitor (C) The metallic tungsten corrosion inhibitor adsorbs to metallic tungsten to form a protective film, and has the function of preventing or suppressing etching by an etching agent.

[0075] The (C) metallic tungsten corrosion inhibitor is not particularly limited, but examples thereof include ammonium salts represented by the following formula (1) and heteroaryl salts having an alkyl group having 5 to 30 carbon atoms.

[0076] [ka]

[0077] In the above formula, R 1 represents an alkyl group having 5 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group, a substituted or unsubstituted aryl(poly)heteroalkylene group, a group represented by the following formula (2):

[0078] [ka]

[0079] In formula (2), Cy is a substituted or unsubstituted (hetero)cycloalkyl group or a substituted or unsubstituted (hetero)aryl group, A is each independently an alkylene having 1 to 5 carbon atoms, r is 0 or 1, and Z is a group represented by the following formula:

[0080] [ka]

[0081] In this case, * indicates the position where it bonds with the nitrogen (N) atom in formula (1). This makes it easier for the compound to adsorb to metallic tungsten, enhancing the corrosion prevention function of metallic tungsten.

[0082] The alkyl group having 5 to 30 carbon atoms is not particularly limited, but examples thereof include 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.

[0083] The alkyl(poly)heteroalkylene group is -(C n H 2n -Z-) m -R 3In this case, n is independently 1 to 5, preferably 1 to 3, and more preferably 1 to 2. m is independently 1 to 5, and preferably 1 to 2. Z is independently an oxygen atom (O), a sulfur atom (S), or a phosphorus atom (P), and 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.

[0084] The alkyl(poly)heteroalkylene group may have a substituent. The substituent is usually R 3 In the case where the alkyl(poly)heteroalkylene group has a substituent, the substituent is not particularly limited, but examples thereof include aryl groups having 6 to 20 carbon atoms such as phenyl groups and naphthyl groups; alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, and propyloxy groups; hydroxy groups; cyano groups; and nitro groups. The alkyl(poly)heteroalkylene group may have one or more substituents.

[0085] The aryl(poly)heteroalkylene group 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 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.

[0086] The aryl(poly)heteroalkylene group may have a substituent. The substituent usually replaces a hydrogen atom of Ar. When the aryl(poly)heteroalkylene group has a substituent, the substituent is not particularly limited, and examples thereof include 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 number of substituents may be one or more.

[0087] In formula (2), Cy represents a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 2 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 15 carbon atoms. Examples of the cycloalkyl group having 3 to 10 carbon atoms include, but are not limited to, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Examples of the heterocycloalkyl group having 2 to 10 carbon atoms include, but are not limited to, a pyrrolidinyl group, a piperidyl group, a tetrahydrofuranyl group, a tetrahydropyranyl group, and a tetrahydrothienyl group. Examples of the aryl group having 6 to 15 carbon atoms include, but are not limited to, a phenyl group. The heteroaryl group having 2 to 15 carbon atoms is not particularly limited, and examples thereof include a pyrrolyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, an isoxazolyl group (an isoxazolyl group), a thiazolyl group, an isothiazolyl group, a pyridyl group, a pyrazyl group, a pyridazyl group, a pyrimidyl group, a quinolyl group, and an isoquinolyl group.

[0088] When the cycloalkyl group having 3 to 10 carbon atoms, the heterocycloalkyl group having 2 to 10 carbon atoms, the aryl group having 6 to 15 carbon atoms, and the heteroaryl group having 2 to 15 carbon atoms have a substituent, the substituent is not particularly limited, and examples thereof include alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group; alkoxy groups having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, and a propyloxy group; a vinyloxy group, a buten-1-eneoxy group, -OC(CF3)= Examples of the substituent include alkenyloxy groups such as a group represented by CF{(CF3)2}; aryl groups having 6 to 10 carbon atoms such as a phenyl group and a tolyl group; heteroaryl groups having 3 to 10 carbon atoms such as a pyrrolyl group, a pyridyl group, an imidazolyl group, an oxazolyl group, an isoxazolyl group, a pyrimidyl group and a 4-amino-2-oxo-1,2-dihydropyrimidin-1-yl group; a hydroxy group; a cyano group; a nitro group; and alkoxy groups having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group and a propyloxy group. The number of substituents may be one or more.

[0089] Each A is independently an alkylene having 1 to 5 carbon atoms. The alkylene having 1 to 5 carbon atoms is not particularly limited, but examples thereof include methylene (-CH2-), ethylene (-C2H4-), propylene (-C3H6-), and isopropylene (-CH(CH3)CH2-).

[0090] Also, r is 0 or 1.

[0091] Furthermore, Z is one of the following formulae:

[0092] [ka]

[0093] In this case, one or two of the hydroxy groups in the structure derived from monophosphate or diphosphate may be in the form of an anion. Specifically, it may have the following structure:

[0094] [ka]

[0095] In this case, in formula (1), R 1 Since there is a counter ion of the ammonium cation in the ammonium salt X - may not have.

[0096] Preferred examples of the group represented by formula (2) include the following structures: [ka]

[0097] Of these, R 1 is preferably an alkyl group having 6 to 20 carbon atoms or a substituted or unsubstituted aryl(poly)oxyalkylene group, more preferably an alkyl group having 8 to 18 carbon atoms or a substituted or unsubstituted phenyl(poly)oxyalkylene group, and even more preferably an octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, phenyloxyethyl (Ph-O-C2H4-) group, phenyldi(oxyethylene) (Ph-(O-C2H4)2-) group, or p-(1,1,3,3-tetramethylbutyl)phenyldi(oxyethylene) (p-CH3C(CH3)2CH2C(CH3)2-Ph-(O-C2H4)2-) group.

[0098] R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

[0099] Examples of the alkyl group having 1 to 18 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, and an octadecyl group.

[0100] When the alkyl group having 1 to 18 carbon atoms has a substituent, examples of the substituent include an aryl group having 6 to 20 carbon atoms, such as a phenyl group or a naphthyl group; an alkoxy group having 1 to 6 carbon atoms, such as a methoxy, ethoxy, or propyloxy group; a hydroxy group; a cyano group; and a nitro group.

[0101] The aryl group having 6 to 20 carbon atoms is not particularly limited, but examples thereof include a phenyl group, a naphthyl group, and a biphenyl group.

[0102] When the aryl group having 6 to 20 carbon atoms has a substituent, examples of the substituent include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, propyl, and isopropyl groups; alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, and propyloxy groups; hydroxy groups; cyano groups; and nitro groups.

[0103] Of these, R 2 is preferably a substituted or unsubstituted alkyl group having 1 to 18 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.

[0104] The 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, or hexafluorophosphate. Of these, X is preferably a halide ion, and more preferably a chloride ion or a bromide ion.

[0105] Specific examples of ammonium salts having an alkyl group having 5 to 30 carbon atoms include ammonium salts having a hexyl group such as hexyltrimethylammonium bromide; ammonium salts having a heptyl group such as tetraheptylammonium bromide; ammonium salts having an octyl group such as octyltrimethylammonium chloride and octyldimethylbenzylammonium chloride; ammonium salts having a decyl group such as decyltrimethylammonium chloride and decyldimethylbenzylammonium chloride; and ammonium salts having a dodecyl group such as dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecylethyldimethylammonium chloride, dodecylethyldimethylammonium bromide, benzyldodecyldimethylammonium chloride, benzyldodecyldimethylammonium bromide, tridodecylmethylammonium chloride, and tridodecylmethylammonium bromide. 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.

[0106] Specific examples of ammonium salts having a substituted or unsubstituted alkyl(poly)heteroalkylene group include trimethylpropyldi(oxyethylene)ammonium chloride, trimethylpropyloxyethylenethioethyleneammonium chloride, and the like.

[0107] Specific examples of ammonium salts having a substituted or unsubstituted aryl(poly)heteroalkylene group include benzyldimethyl-2-{2-[4-(1,1,3,3-tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride (benzethonium chloride) and benzyldimethylphenyldi(oxyethylene)ammonium chloride.

[0108] Specific examples of ammonium salts having a group represented by formula (2) include compounds represented by the following structures.

[0109] [ka]

[0110] The heteroaryl salt having an alkyl group having 5 to 30 carbon atoms is not particularly limited, but examples thereof include salts of a heteroaryl cation in which at least one nitrogen atom in a substituted or unsubstituted nitrogen-atom-containing heteroaryl ring is bonded to an alkyl group having 5 to 30 carbon atoms.

[0111] 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.

[0112] When the nitrogen atom-containing heteroaryl ring has a substituent, examples of the substituent include alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, and an isopropyl group; 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.

[0113] The alkyl group having 5 to 30 carbon atoms is not particularly limited, but examples thereof include 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.

[0114] Of these, the alkyl group having 5 to 30 carbon atoms is preferably an alkyl group having 6 to 20 carbon atoms, more preferably an alkyl group having 8 to 18 carbon atoms, and even more preferably an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, or an octadecyl group.

[0115] The counter anion of the heteroaryl cation having an alkyl group having 5 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; and hexafluorophosphate. Among these, the counter anion is preferably a halide ion, and more preferably a chloride ion or a bromide ion.

[0116] Specific examples of heteroaryl salts having an alkyl group having 5 to 30 carbon atoms include 1-methyl-3-hexylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium bromide, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium bromide, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium chloride, and 1-dodecyl-3-methylimidazolium chloride. Imidazolium salts such as 1-hexyl-3-methylimidazolium bromide, 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; 3-dodecyloxazolium chloride, 3-dodecyloxazolium bromide, 3-tetradecyloxazolium chloride, and 3-hexadecyloxazolium bromide. Oxazolium salts such as 3-dodecyloxazolium chloride; thiazolium salts such as 3-dodecylthiazolium chloride, 3-dodecylthiazolium bromide, 3-dodecyl-4-methylthiazolium chloride, 3-tetradecylthiazolium chloride, and 3-hexadecylthiazolium chloride; 1-hexylpyridinium chloride, 1-octylpyridinium chloride, 1-decylpyridinium chloride, 1-dodecylpyridinium chloride, 1-dodecylpyridinium bromide, 1-tetradecylpyridinium chloride, and 1-tetradecylpyridinium chloride. Pyridinium salts such as pyridinium bromide, 1-hexadecylpyridinium chloride, 1-hexadecylpyridinium bromide, 1-octadecylpyridinium chloride, and 1-octadecylpyridinium bromide; pyrimidinium salts such as 1-hexylpyrimidinium chloride, 1-hexylpyrimidinium hexafluorophosphate, 1-octylpyrimidinium chloride, 1-decylpyrimidinium chloride, 1-dodecylpyrimidinium chloride, 1-tetradecylpyrimidinium chloride, and 1-hexadecylpyrimidinium chloride;Examples of the quinolinium salts include dodecylquinolinium chloride, dodecylquinolinium bromide, tetradecylquinolinium chloride, and hexadecylquinolinium chloride; and isoquinolinium salts include dodecylisoquinolinium chloride, dodecylisoquinolinium bromide, tetradecylisoquinolinium chloride, and hexadecylisoquinolinium chloride. These may also be used as hydrates.

[0117] Among these, (C) the metal tungsten corrosion inhibitor is an ammonium salt represented by formula (1) (where R 1 is an alkyl group having 6 to 20 carbon atoms, and R 2 is an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms substituted with an aryl group having 6 to 20 carbon atoms), an ammonium salt having a substituted or unsubstituted aryl (poly)heteroalkylene group, or a heteroaryl salt having an alkyl group having 5 to 30 carbon atoms, and the ammonium salt represented by formula (1) (wherein R 1 is an alkyl group having 8 to 20 carbon atoms, and R 2is an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms substituted with a phenyl group), an ammonium salt having a substituted or unsubstituted phenyl(poly)oxyalkylene group, or an imidazolium salt having an alkyl group having 8 to 20 carbon atoms is more preferred, and examples thereof include octyltrimethylammonium salt, octyldimethylbenzylammonium salt, decyltrimethylammonium salt, decyldimethylbenzylammonium salt, dodecyltrimethylammonium salt, dodecyldimethylbenzylammonium salt, tetradecyltrimethylammonium salt, tetradecyldimethylbenzylammonium salt, hexadecyltrimethylammonium salt, hexadecyldimethylbenzylammonium salt, octadecyltrimethylammonium salt, octadecyldimethylbenzylammonium salt, octyltriethylammonium salt, octyldiethylbenzylammonium salt, and decyltriethylammonium salt. , decyldiethylbenzylammonium salt, dodecyltriethylammonium salt, dodecyldiethylbenzylammonium salt, tetradecyltriethylammonium salt, tetradecyldiethylbenzylammonium salt, hexadecyltriethylbenzylammonium salt, hexadecyldiethylbenzylammonium salt, octadecyltriethylammonium salt, octadecyldiethylbenzylammonium salt, octylethylmethylbenzylammonium salt, decylethylmethylbenzylammonium salt, dodecylethylmethylbenzylammonium salt, tetradecylethylmethylbenzylammonium salt, hexadecylethylmethylbenzylammonium salt, octadecylethylmethylbenzylammonium salt, trimethyl-2-{2-[4-(1,1,3,3-tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride, benzyldimethyl-2-{2-[4-(1,1,3,3-Tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride (benzethonium chloride), 1-octylimidazolium chloride, 1-decylimidazolium chloride, 1-dodecylimidazolium chloride, 1-tetradecylimidazolium chloride, 1-hexadecylimidazolium chloride, 1-octadecylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium chloride, 1-hexadecyl-3-methylimidazolium chloride, 1-octadecyl-3-methylimidazolium chloride More preferred are 1-octyldimethylbenzylammonium salt, decyldimethylbenzylammonium salt, dodecyldimethylbenzylammonium salt, tetradecyldimethylbenzylammonium salt, hexadecyldimethylbenzylammonium salt, octadecyldimethylbenzylammonium salt, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium chloride, 1-hexadecyl-3-methylimidazolium chloride, and 1-octadecyl-3-methylimidazolium chloride.

[0118] The above-mentioned (C) metallic tungsten corrosion inhibitors may be used alone or in combination of two or more. That is, in a preferred embodiment, the (C) metallic tungsten corrosion inhibitor preferably contains at least one selected from the group consisting of ammonium salts having an alkyl group containing 5 to 30 carbon atoms, ammonium salts having a substituted or unsubstituted aryl (poly)heteroalkylene group, and heteroaryl salts having an alkyl group containing 5 to 30 carbon atoms. From the viewpoint of a high Ti / W etching selectivity, the (C) metallic tungsten corrosion inhibitor preferably contains at least one selected from the group consisting of an ammonium salt represented by formula (1) (wherein R 1 is an alkyl group having 6 to 20 carbon atoms, and R 2is an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms substituted with an aryl group having 6 to 20 carbon atoms), an ammonium salt having a substituted or unsubstituted phenyl(poly)oxyalkylene group, and a heteroaryl salt having an alkyl group having 5 to 30 carbon atoms, and the ammonium salt represented by formula (1) (wherein R 1 is an alkyl group having 8 to 20 carbon atoms, and R 2is an alkyl group having 1 to 10 carbon atoms, or an alkyl group having 1 to 5 carbon atoms substituted with a phenyl group), and imidazolium salts having an alkyl group having 8 to 20 carbon atoms, and the imidazolium salts preferably contain at least one selected from the group consisting of octyltrimethylammonium salt, octyldimethylbenzylammonium salt, decyltrimethylammonium salt, decyldimethylbenzylammonium salt, dodecyltrimethylammonium salt, dodecyldimethylbenzylammonium salt, tetradecyltrimethylammonium salt, tetradecyldimethylbenzylammonium salt, hexadecyltrimethylammonium salt, hexadecyldimethylbenzylammonium salt, octadecyltrimethylammonium salt, octadecyldimethylbenzylammonium salt, octyltriethylammonium salt, octyldiethylbenzylammonium salt, decyltriethylammonium salt, decyldiethylbenzylammonium salt, Ethylbenzylammonium salt, dodecyltriethylammonium salt, dodecyldiethylbenzylammonium salt, tetradecyltriethylammonium salt, tetradecyldiethylbenzylammonium salt, hexadecyltriethylammonium salt, hexadecyldiethylbenzylammonium salt, octadecyltriethylammonium salt, octadecyldiethylbenzylammonium salt, octylethylmethylbenzylammonium salt, decylethylmethylbenzylammonium salt, dodecylethylmethylbenzylammonium salt, tetradecylethylmethylbenzylammonium salt, hexadecylethylmethylbenzylammonium salt, octadecylethylmethylbenzylammonium salt, trimethyl-2-{2-[4-(1,1,3,3-tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride, benzyldimethyl-2-{2-[4-(1,1,3,a small amount selected from the group consisting of 3-tetramethylbutyl)phenoxy]ethoxy}ethylammonium chloride (benzethonium chloride), 1-octylimidazolium chloride, 1-decylimidazolium chloride, 1-dodecylimidazolium chloride, 1-tetradecylimidazolium chloride, 1-hexadecylimidazolium chloride, 1-octadecylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium chloride, 1-hexadecyl-3-methylimidazolium chloride, and 1-octadecyl-3-methylimidazolium chloride; It is particularly preferred that the compound contains at least one of the following, and it is most preferred that the compound contains at least one selected from the group consisting of octyldimethylbenzyl ammonium salt, decyldimethylbenzyl ammonium salt, dodecyldimethylbenzyl ammonium salt, tetradecyldimethylbenzyl ammonium salt, hexadecyldimethylbenzyl ammonium salt, octadecyldimethylbenzyl ammonium salt, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride, 1-tetradecyl-3-methylimidazolium chloride, 1-hexadecyl-3-methylimidazolium chloride, and 1-octadecyl-3-methylimidazolium chloride.

[0119] The addition rate of (C) the metal tungsten corrosion inhibitor 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 agent.

[0120] pH adjuster The etching agent may contain a pH adjuster as needed. Examples of the pH adjuster include (A) an oxidizing agent and (B) an acid or alkali other than a fluorine compound.

[0121] 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.

[0122] 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.

[0123] Of the above, the pH adjuster is preferably hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, methanesulfonic acid, or ammonia, more preferably sulfuric acid, nitric acid, or ammonia, and even more preferably sulfuric acid or nitric acid.

[0124] solvent The etching agent preferably contains a solvent, which has the functions of uniformly dispersing the components contained in the etching agent, diluting the etching agent, etc.

[0125] The solvent includes water and organic solvents.

[0126] 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.

[0127] The organic solvent is not particularly limited, and examples thereof include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and tert-butanol; polyhydric alcohols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethylhexane-1,3-diol, and glycerin; and glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl 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.

[0128] Of the above, the solvent is more preferably water. The solvents may be used alone or in combination of two or more.

[0129] The ratio of the solvent, particularly water, added 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, relative to the total mass of the etching agent.

[0130] Iodine Scavenger When the oxidizing agent (A) contains an oxoacid of iodine, the etching agent preferably further contains an iodine scavenger.

[0131] 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 suitable iodine scavengers 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 scavengers are preferably aliphatic ketones, more preferably 4-methyl-2-pentanone, 5-methyl-3-pentanone, 2,4-dimethyl-3-pentanone, and cyclohexanone, and even more preferably 4-methyl-2-pentanone. These iodine scavengers may be used alone or in combination of two or more.

[0132] Low Dielectric Passivator The etching agent 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.

[0133] Examples of low dielectric constant passivation agents include, but are not limited to, 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.

[0134] These low dielectric constant passivators may be used alone or in combination of two or more.

[0135] 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 %, relative to the total mass of the etching agent.

[0136] additives The etching agent may further contain additives such as surfactants, chelating agents, antifoaming agents, silicon-containing compounds, etc.

[0137] Etching agent properties The pH of the etching agent is preferably 0.5 to 5.0, more preferably 1.0 to 4.0, and even more preferably 1.0 to 3.0.

[0138] The etching rate of the tungsten metal of the etching agent is preferably 5.0 Å / min or less, more preferably 3.0 Å / min or less, even more preferably 2.0 Å / min or less, particularly preferably 1.5 Å / min or less, and most preferably 0.1 to 1.0 Å / min. A tungsten metal etching rate of 5.0 Å / min or less is preferable because it increases the Ti / W etching selectivity. The tungsten metal etching rate of the etching agent refers to a value measured by the method in the examples.

[0139] The etching rate of the titanium and titanium alloy of the etching agent is preferably 10 Å / min or more, more preferably 30 Å / min or more, even more preferably 50 Å / min or more, even more preferably 60 Å / min or more, and particularly preferably 80 Å / min or more. An etching rate of 10 Å / min or more for titanium and titanium alloys is preferable because it increases the Ti / W etching selectivity. The etching rates of titanium and titanium alloys of the etching agent refer to values ​​measured by the methods in the examples.

[0140] The etching rate of the insulating layer material of the etching agent is preferably 5.0 Å / min or less, more preferably 3.0 Å / min or less, even more preferably 2.0 Å / min or less, particularly preferably 1.5 Å / min or less, and most preferably 1.0 Å / min or less. An etching rate of the insulating layer material of 5.0 Å / min or less is preferable because it maintains the shape of the semiconductor substrate and improves the performance of the semiconductor element. The etching rate of the insulating layer material of the etching agent refers to a value measured by the method in the examples.

[0141] The Ti / W etching selectivity of the etching agent (etching rate of titanium or titanium alloy / etching rate of metal tungsten) is preferably 10 or more, more preferably 30 or more, even more preferably 35 or more, particularly preferably 70 or more, and most preferably 100 or more. A Ti / W etching selectivity of 10 or more is preferable because it allows the production of high-performance semiconductor substrates for memory devices.

[0142] (contact) The method for contacting the semiconductor substrate with the etching agent after step (1) is not particularly limited, and known techniques can be appropriately adopted. Specifically, the semiconductor substrate may be immersed in the etching agent, or the etching agent 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, or the dripping may be repeated two or more times, or immersion, spraying, and dripping may be combined.

[0143] 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.

[0144] The contact time is not particularly limited, but is preferably from 10 seconds to 3 hours, more preferably from 30 seconds to 1 hour, further preferably from 1 to 45 minutes, and particularly preferably from 1 to 5 minutes.

[0145] By contacting the semiconductor substrate after step (1) with an etching agent, the titanium and titanium alloy can be selectively etched. Since at least a portion of the tungsten oxide film has been removed in step (1), the selective etching of the titanium and titanium alloy by the etching agent proceeds more smoothly.

[0146] (Semiconductor substrate for memory devices) The semiconductor substrate for memory devices obtained by the step (2) can be used for memory devices such as DRAMs, etc. The memory devices obtained by the step (2) can be made smaller and more highly functional.

[0147] <Kit> According to one aspect of the present invention, a kit is provided. The kit includes the pretreatment agent and the etching agent described above. That is, the kit is used for manufacturing semiconductor substrates for memory devices. The kit containing the pretreatment agent and the etching agent is convenient for carrying out the above-described steps (1) and (2) when selectively etching titanium / titanium alloy on a semiconductor substrate having a tungsten oxide film. [Example]

[0148] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0149] [Example 1] (Process (1)) A substrate having a tungsten oxide (WO3) film, a substrate having a metallic tungsten (W) film, a substrate having a titanium nitride (TiN) film, and a substrate having a silicon oxide (th-Ox) film were prepared, and step (1) was performed on each substrate, and the etching rate of the pretreatment agent for each film was measured.

[0150] A pretreatment agent was prepared. Specifically, hydrogen fluoride (HF), a WO3 etchant, was added to pure water and stirred to prepare the pretreatment agent. The hydrogen fluoride content was 0.1 mass% relative to the total mass of the pretreatment agent. The pH of the pretreatment agent was 2.2. The pH of the pretreatment agent was measured at 23°C using a benchtop pH meter (F-71) and a pH electrode (9615S-10D) manufactured by Horiba, Ltd.

[0151] (1-A) Treatment of substrates with tungsten oxide (WO3) film Tungsten oxide (WO3) was deposited on a silicon wafer by physical vapor deposition to a thickness of 3000 Å, and then placed on a 1cm x 1cm (immersion treatment area: 1cm 2 ) to prepare a tungsten oxide film sample.

[0152] A tungsten oxide film sample was immersed in 10 g of the prepared pretreatment agent at a predetermined treatment temperature for 5 minutes. After the immersion treatment, the pretreatment agent was diluted 10 to 20 times with a 1% by mass aqueous solution of nitric acid to prepare a measurement sample. The tungsten concentration in the measurement sample was measured using an Avio200 (PerkinElmer) inductively coupled plasma optical emission spectrometer (ICP-OES).

[0153] The samples for creating a calibration curve were prepared as follows: A tungsten standard solution (tungsten concentration: 1000 ppm, manufactured by Fujifilm Wako Co., Ltd.) was diluted with a 1% by mass aqueous solution of nitric acid to prepare samples for creating a calibration curve with tungsten concentrations of 25 ppb, 12.5 ppb, and 2.5 ppb.

[0154] The tungsten concentration before dilution was calculated from the tungsten concentration of the measurement sample calculated using the sample for creating a calibration curve, and the etching amount of the tungsten oxide film was calculated by substituting the tungsten concentration before dilution and the amount of pretreatment agent used in the measurement (amount of the measurement sample before dilution) into the following equation.

[0155]

number

[0156] In the above formula, 231.84 (g / mol) is the molecular weight of tungsten oxide (WO3), and 7.16 (g / cm 3 ) is the density of tungsten oxide, and 1cm 2 is the immersion treatment area of ​​the tungsten oxide film sample, and 183.84 (g / mol) is the molecular weight of metallic tungsten (W).

[0157] The etching rate (ER) of the tungsten oxide film was calculated by dividing the calculated amount of etching of the tungsten oxide film by the time of immersion treatment using the pretreatment agent. As a result, the etching rate (ER) of the tungsten oxide film using the pretreatment agent was 31 Å / min.

[0158] (1-B) Processing of a substrate with a metal tungsten (W) film Tungsten (W) was deposited on a silicon wafer by physical vapor deposition to a thickness of 1000 Å, and the resulting film was 1 cm x 1 cm (immersion treatment area: 1 cm 2 ) to prepare a metallic tungsten film sample.

[0159] The measurement sample was prepared and the tungsten concentration in the measurement sample was measured in the same manner as the method for measuring the etching rate of the tungsten oxide film, except that a metallic tungsten film sample was used and the immersion time was 2 minutes.

[0160] The tungsten concentration before dilution was calculated from the tungsten concentration of the measurement sample calculated using the sample for creating a calibration curve, and the etching amount of the metallic tungsten film was calculated by substituting the tungsten concentration before dilution and the amount of pretreatment agent used in the measurement (amount of the measurement sample before dilution) into the following equation.

[0161]

number

[0162] In the above formula, 19.25 (g / cm 3 ) is the density of metallic tungsten, and 2 is the immersion treatment area of ​​the tungsten film sample.

[0163] The etching rate (ER) of the tungsten metal film was calculated by dividing the calculated amount of etching by the time of immersion treatment using the pretreatment agent. As a result, the etching rate (ER) of the tungsten metal film by the pretreatment agent was 2.5 Å / min.

[0164] (1-C) Treatment of substrates with titanium nitride (TiN) films Titanium nitride (TiN) was deposited on a silicon wafer by physical vapor deposition to a thickness of 1000 Å, and then placed on a 2 cm x 2 cm (immersion treatment area: 4 cm 2 ) to prepare a titanium nitride film sample.

[0165] The thickness of the titanium nitride film sample was measured using a fluorescent X-ray analyzer EA1200VX (manufactured by Hitachi High-Tech).

[0166] The titanium nitride film-formed sample was immersed in 10 g of the prepared pretreatment agent at a predetermined treatment temperature for 5 minutes.

[0167] The thickness of the titanium nitride film sample after the pretreatment immersion treatment was measured in the same manner as above.

[0168] The difference in film thickness of the titanium nitride film sample before and after immersion in the pretreatment agent was calculated, and the etch rate (ER) of the titanium nitride film was calculated by dividing this by the immersion time using the pretreatment agent. As a result, the etch rate (ER) of the titanium nitride film by the pretreatment agent was found to be 5 Å / min.

[0169] (1-D) Treatment of substrates with silicon oxide (th-Ox) films Silicon oxide was formed on the silicon wafer by thermal oxidation to a thickness of 1000 Å, and then placed on a 1cm x 1cm (immersion treatment area: 1cm 2 ) to prepare silicon oxide film samples.

[0170] The film thickness of the silicon oxide film sample was measured using an optical film thickness meter n&k1280 (manufactured by n&k Technology Co., Ltd.).

[0171] The silicon oxide film-formed sample was immersed in 10 g of the prepared pretreatment agent at a predetermined treatment temperature for 30 minutes.

[0172] The thickness of the silicon oxide film-formed sample after the immersion treatment was measured in the same manner as above.

[0173] The etching rate (ER) of the silicon oxide film was calculated by calculating the difference in film thickness of the silicon oxide film sample before and after treatment and dividing it by the time spent immersed in the pretreatment agent. As a result, the etching rate (ER) of the silicon oxide film by the pretreatment agent was 2.8 Å / min.

[0174] (1-E) Calculation of WO3 / W etching selectivity The etching rate (ER) of the tungsten oxide film using the pretreatment agent was divided by the etching rate (ER) of the tungsten metal film using the pretreatment agent to calculate the WO3 / W etching selectivity, which was found to be 12.

[0175] (Process (2)) Step (2) was performed on a substrate having a metallic tungsten (W) film, a substrate having a titanium nitride (TiN) film, and a substrate having a silicon oxide (th-Ox) film, and the etching rate of the etching agent for each film was measured. For the substrate having a titanium nitride (TiN) film, a titanium nitride film sample after step (1) was used. For the substrate having a metallic tungsten (W) film and the substrate having a silicon oxide (th-Ox) film, a metallic tungsten film sample and a silicon oxide film sample newly prepared separately by the same method as step (1) were used.

[0176] An etching agent was prepared. Specifically, iodic acid (HIO3), an oxidizing agent, hydrogen fluoride (HF), a fluorine compound, and 1-dodecylpyridinium chloride (DPC), a metal tungsten corrosion inhibitor, were added to pure water and stirred to prepare the etching agent. The addition rates of iodic acid, hydrogen fluoride, and 1-dodecylpyridinium chloride (DPC) were 0.018 mass%, 0.05 mass%, and 0.005 mass%, respectively, relative to the total mass of the etching agent. The pH of the etching agent was 2.4.

[0177] (2-A) Processing of a substrate with a metal tungsten (W) film A metallic tungsten film sample was immersed in 10 g of the prepared etching agent at a predetermined treatment temperature for 2 minutes. The etching rate (ER) of the metallic tungsten film was calculated using the same method as in (1-B) above. The etching rate (ER) of the metallic tungsten film by the etching agent was found to be 2.1 Å / min.

[0178] (2-B) Treatment of the substrate having the titanium nitride (TiN) film after step (1) The titanium nitride film sample after step (1) was immersed in 10 g of the prepared etching agent at a predetermined treatment temperature for 2 minutes. The etching rate (ER) of the titanium nitride film was calculated using the same method as in (1-C) above. The etching rate (ER) of the titanium nitride film by the etching agent was found to be 85 Å / min.

[0179] (2-C) Treatment of substrates with silicon oxide (th-Ox) films A silicon oxide film sample was immersed in 10 g of the prepared etching agent at a predetermined treatment temperature for 30 minutes. The etching rate (ER) of the silicon oxide film was calculated using the same method as in (1-D) above. The etching rate (ER) of the silicon oxide film by the etching agent was found to be 0.8 Å / min.

[0180] (2-D) TiN / W etching selectivity The etching rate (ER) of the titanium nitride film by the etching agent was divided by the etching rate (ER) of the metal tungsten film by the etching agent to calculate the TiN / W etching selectivity, which was found to be 40.

[0181] [evaluation] The pretreatment agent was evaluated for its corrosion potential difference between metallic tungsten (W) and titanium nitride (TiN) and its ability to remove titanium oxide.

[0182] (Corrosion potential difference between metallic tungsten (W) and titanium nitride (TiN)) The corrosion potential of metallic tungsten (W) was measured using the following method. Specifically, linear sweep voltammetry measurements were performed using a Hokuto Denko HZ7000. Specifically, a metallic tungsten film immersed in 0.5% ammonia water at 23°C for 1 minute was used as the working electrode, a platinum counter electrode, and a silver / silver chloride (3.3 M potassium chloride aqueous solution) and salt bridge (agar containing 0.5 M potassium chloride) reference electrode. A potential was applied to the metallic tungsten at a rate of 2 mV / s from a potential 30 mV to 200 mV lower than the corrosion potential, and the current values ​​at each potential were plotted (Tafel plot). The potential at which the current value was lowest was defined as the corrosion potential of metallic tungsten. The corrosion potential of metallic tungsten (W) was found to be -109 mV.

[0183] The corrosion potential of titanium nitride (TiN) was measured using the following method. Specifically, linear sweep voltammetry measurements were performed using a Hokuto Denko HZ7000. Specifically, a titanium nitride film immersed in a 1% by mass hydrogen fluoride solution at 23°C for 1 minute was used as the working electrode, a platinum counter electrode, and a silver / silver chloride (3.3 M potassium chloride solution) and a salt bridge (agar containing 0.5 M potassium chloride) reference electrode. A potential was applied to the titanium nitride at a rate of 2 mV / s from a potential 30 mV to 200 mV below the corrosion potential, and the current values ​​at each potential were plotted (Tafel plot). The potential at which the current value was lowest was defined as the corrosion potential of titanium nitride. The resulting corrosion potential of titanium nitride (TiN) was −73 mV.

[0184] The corrosion potential difference between metallic tungsten (W) and titanium nitride (TiN) (corrosion potential of W - corrosion potential of TiN) was calculated to be 36 mV.

[0185] (Titanium oxide removal ability) Titanium nitride (TiN) was deposited on a silicon wafer by physical vapor deposition to a thickness of 1000 Å, and then placed on a 2 cm x 2 cm (immersion treatment area: 4 cm 2 The surface of the formed titanium nitride film was then oxidized by exposing it to the atmosphere at 20°C for 30 days, to prepare a sample for measuring the titanium oxide removal ability.

[0186] The sample for measuring titanium oxide removal ability was immersed in 10 g of the pretreatment agent (0.1 mass % HF aqueous solution) prepared in step (1) at 30°C for 5 minutes to obtain a pretreated sample. The etching rate (ER) of the titanium nitride film was then calculated using the etching agent prepared in step (2) in the same manner as in (2-B), and was found to be 85 Å / min. The higher the etching rate (ER) of the titanium nitride film, the more successfully the titanium oxide film was removed by the pretreatment agent in step (1).

[0187] [Examples 1-2 to 1-10] Pretreatment agents were prepared by changing the components added as shown in Table 1 below. The compositions of the pretreatment agents are shown in Table 1 below, along with the composition of Example 1.

[0188] [Table 1]

[0189] Furthermore, step (1) was carried out in the same manner as in Example 1. The measurement results of the etching rates (ER) of a tungsten oxide (W) film, a metallic tungsten (W) film, a titanium nitride (TiN) film, and a silicon oxide film, the WO3 / W etching selectivity, the corrosion potential of metallic tungsten (W), the corrosion potential of titanium nitride (TiN), and the corrosion potential difference between metallic tungsten (W) and titanium nitride (TiN), and the titanium oxide removal ability are shown in Table 2 below, along with the results of Example 1. The same etching agent as used in Example 1 was used as the etching agent used in measuring the titanium oxide removal ability.

[0190] [Table 2]

[0191] The results in Table 2 show that Example 1 and Examples 1-2 to 1-10 all have a high etching rate (ER) of WO3. Therefore, Example 1 and Examples 1-2 to 1-10 do not reduce throughput and can prevent etching of metallic tungsten during pretreatment. Therefore, by performing step (2) using the semiconductor substrate obtained in step (1), a high-performance semiconductor substrate for memory devices can be manufactured with high production efficiency.

[0192] [Examples 2-2 to 2-10] Etching agents were prepared by changing the components to be added as shown in Table 3 below. The compositions of the etching agents are shown in Table 3 below, along with the composition of the etching agent of Example 1.

[0193] [Table 3]

[0194] The DPC, CPC, DMIC, CTAB, OMIC, and BZC used in the examples have the following structures:

[0195] [ka]

[0196] As in Example 1, step (2) was performed on a substrate having a metal tungsten (W) film, a substrate having a titanium nitride (TiN) film, and a substrate having a silicon oxide (th-Ox) film. For the substrate having a titanium nitride (TiN) film, a titanium nitride film sample obtained after step (1) was used. For the substrate having a metal tungsten (W) film and the substrate having a silicon oxide (th-Ox) film, a metal tungsten film sample and a silicon oxide film sample newly prepared by the same method as step (1) were used. The measurement results of the etching rates (ER) of the metal tungsten (W) film, titanium nitride (TiN) film, and silicon oxide film, as well as the TiN / W etching selectivity, are shown in Table 4 below, along with the results of Example 1.

[0197] [Table 4]

[0198] The results in Table 4 show that in Example 1 and Examples 2-2 to 2-10, tungsten oxide is efficiently removed in step (1), allowing titanium nitride to be selectively etched in step (2), and high-performance semiconductor substrates for memory elements can be manufactured with high production efficiency. [Explanation of symbols]

[0199] 10 Semiconductor substrate (before process (1)) 11 Silicon substrate having a recess 12 insulating film 13 Barrier film 14 Metallic tungsten film 15 Tungsten oxide film 16 Titanium oxide film 20 Semiconductor substrate (after process (1)) 21 Silicon substrate having a recess 22 insulating film 23 Barrier Film 24 Metallic tungsten film 30 Semiconductor substrate (after process (2)) 31 Silicon substrate with recess 32 insulating film 33 Etched barrier film 34 Metallic tungsten film

Claims

1. (1) a step of contacting a semiconductor substrate having a titanium-containing film containing at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film with a pretreatment agent to remove at least a portion of the tungsten oxide film; (2) contacting the semiconductor substrate after step (1) with an etching agent to remove at least a portion of the titanium-containing film; Including, the pretreatment agent includes a tungsten oxide etchant, the tungsten oxide etchant comprises at least one selected from the group consisting of acid, ammonium fluoride, and ammonium bifluoride; A method for manufacturing a semiconductor substrate for a memory element, wherein the content of the tungsten oxide etchant is 0.03 to 3 mass % relative to the total mass of the treatment agent.

2. The method according to claim 1, wherein the pretreatment agent has a pH of 0.1 to 13.

3. 3. The manufacturing method according to claim 1, wherein the tungsten oxide etchant comprises at least one selected from the group consisting of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, and phosphoric acid.

4. the semiconductor substrate further comprises a titanium oxide film; The manufacturing method according to any one of claims 1 to 3, wherein the step (1) further comprises removing at least a portion of the titanium oxide film.

5. the etching agent comprises (A) an oxidizing agent, (B) a fluorine compound, and (C) a metal tungsten corrosion inhibitor; the addition rate of the oxidizing agent (A) is 0.0001 to 10 mass% relative to the total mass of the etching agent, the addition rate of the (B) fluorine compound is 0.005 to 10 mass% relative to the total mass of the etching agent, 5. The manufacturing method according to claim 1, wherein an addition rate of the (C) metal tungsten corrosion inhibitor is 0.0001 to 5 mass % relative to the total mass of the etching agent.

6. The method according to claim 5, wherein the oxidizing agent (A) comprises at least one selected from the group consisting of peracids, halogen oxoacids, and salts thereof.

7. The (B) fluorine compound 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 7. The method according to claim 5, wherein the compound is at least one selected from the group consisting of methyl methyl acrylate, methyl meth ...

8. The (C) metal tungsten corrosion inhibitor is represented by the following formula (1): 【Chemistry 1】 (In the above formula (1), R １ represents an alkyl group having 5 to 30 carbon atoms, a substituted or unsubstituted alkyl(poly)heteroalkylene group, a substituted or unsubstituted aryl(poly)heteroalkylene group, a group represented by the following formula (2): 【Chemistry 2】 (In the above formula, Cy is a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 2 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 15 carbon atoms; each A is independently an alkylene group having 1 to 5 carbon atoms; r is 0 or 1; Z is a group represented by the following formula: 【Transformation 3】 Either is a group represented by R ２ are each independently a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, X is a halide ion, a hydroxide ion, an organic sulfonate ion, tetrafluoroborate, or hexafluorophosphate. and heteroaryl salts having an alkyl group having 5 to 30 carbon atoms.

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