Substrate manufacturing method

Abstract

In one embodiment, a method for manufacturing a substrate is provided that can suppress the generation of water-insoluble substances and suppress the residue adhering to the substrate. [Solution] In one embodiment, this disclosure relates to a method for manufacturing a substrate, comprising the following steps 1 and 2, wherein steps 1 and 2 are performed sequentially. Step 1: A step of etching the etchable layer of a substrate having an etchable layer containing a Group 6 element metal with a composition containing phosphoric acid, nitric acid, and an organic acid. Step 2: A step in which the substrate obtained in Step 1 is washed with an acid with a pKa of 4 or less.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a substrate and a method for processing a substrate after etching.

Background Art

[0002] In the manufacturing process of semiconductor devices, for example, a step of etching an etched layer containing at least one metal such as tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, rhodium, copper, nickel, cobalt, titanium, titanium nitride, alumina, aluminum, and iridium into a predetermined pattern shape is performed. In recent years, in the semiconductor field, high integration has been progressing, and the complexity and miniaturization of wiring are required. The requirements for pattern processing technology and etching solutions are also increasing, and various etching solutions and etching methods have been proposed.

[0003] For example, in Patent Document 1, as a chemical solution used for etching a layer containing molybdenum, a chemical solution containing a mixed acid and polyethyleneimine which is an organic amine is proposed. The mixed acid contains an inorganic acid, an oxidizing agent, a carboxylic acid, and water, and the concentration of polyethyleneimine in the chemical solution is in the range of 0.05 wt% to 10 wt%. In Patent Document 2, as an etching composition capable of selectively etching cobalt, a compound of the formula: R1-O-N-R2R3 (where each of R1, R2, and R3 is independently H or C1-C6 alkyl), at least one unsaturated C3-C 12 A carboxylic acid, at least one leveling agent, and water are proposed. In paragraph 0059 and the like of the same document, it is described that the semiconductor substrate after etching may be rinsed with a rinsing solvent, and examples of the rinsing solvent include alcohols and aqueous rinsing agents with pH > 8.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-147744 [Patent Document 2] Special Publication No. 2022-530669 [Overview of the project] [Problems that the invention aims to solve]

[0005] As an etching solution, a mixed acid aqueous solution (strong acid aqueous solution) containing phosphoric acid is commonly used. However, if etching is performed using an etching solution containing phosphoric acid, nitric acid, and organic acids, followed by water washing, water-insoluble substances may precipitate. Such precipitates adhere to the substrate and become residue.

[0006] Therefore, this disclosure provides a method for manufacturing a substrate and a method for processing a substrate that can suppress the generation of water-insoluble substances and suppress the residue adhering to the substrate. [Means for solving the problem]

[0007] This disclosure relates, in one embodiment, to a method for manufacturing a substrate, comprising the following steps 1 and 2, wherein steps 1 and 2 are performed sequentially. Step 1: A step of etching the etchable layer of a substrate having an etchable layer containing a Group 6 element metal with a composition containing phosphoric acid, nitric acid, and an organic acid. Step 2: A step in which the substrate obtained in Step 1 is washed with an acid with a pKa of 4 or less.

[0008] This disclosure relates to a substrate processing method in one embodiment, comprising a step of cleaning the substrate to be processed with an acid having a pKa of 4 or less (cleaning step), wherein the substrate to be processed is a substrate having a metal layer containing a group 6 elemental metal, which has been etched with a composition containing phosphoric acid, nitric acid, and an organic acid, and the cleaning step is performed immediately after etching the substrate having the metal layer containing the group 6 elemental metal. [Effects of the Invention]

[0009] According to this disclosure, in one embodiment, a method for manufacturing a substrate can be provided that can suppress the generation of water-insoluble substances and suppress the residue adhering to the substrate. [Modes for carrying out the invention]

[0010] This disclosure is based on the finding that, in one embodiment, by washing a substrate after etching using a composition containing phosphoric acid, nitric acid, and an organic acid with a specific acid before washing with water, the generation of water-insoluble substances can be suppressed and residue adhering to the substrate can be suppressed.

[0011] This disclosure relates, in one embodiment, to a method for manufacturing a substrate (hereinafter also referred to as "the substrate manufacturing method of this disclosure") which includes the following steps 1 and 2, and which involves performing steps 1 and 2 in succession. Step 1: A step of etching the layer to be etched of a substrate having an etchable layer containing a Group 6 elemental metal with a composition containing phosphoric acid, nitric acid, and an organic acid (hereinafter also referred to as the "etching solution") (hereinafter also referred to as the "etching step"). Step 2: A step in which the substrate obtained in Step 1 is cleaned with an acid with a pKa of 4 or less (hereinafter also referred to as the "rinsing solution") (hereinafter also referred to as the "cleaning step").

[0012] Although the detailed mechanism of how the effects of this disclosure are realized is not clear, it is presumed to be as follows. In a composition (etching solution) containing phosphoric acid, nitric acid, and organic acids, as etching progresses, the metal dissolved from the etched layer interacts with the compounds present in the etching solution to form a complex. This complex precipitates as a water-insoluble substance when the substrate is washed with water after etching. In this disclosure, it is believed that by performing cleaning with an acid with a pKa of 4 or less, which is a rinse solution with high solubility for the composite, after etching and before water rinsing, water-insoluble substances will not precipitate, and residue adhering to the substrate can be suppressed. However, this disclosure does not have to be construed as being limited to these mechanisms.

[0013] [Substrate having an etchable layer containing Group 6 element metals] In this disclosure, the layer to be etched is, in one or more embodiments, a metal layer containing a Group 6 elemental metal. The metal layer may consist solely of a Group 6 elemental metal, or it may be a metal layer that is an alloy containing a Group 6 elemental metal. As the Group 6 elemental metal, at least one metal selected from tungsten and molybdenum is preferred, for example. As the layer to be etched, in one or more embodiments, examples include a tungsten film (layer) or a molybdenum film (layer). In this disclosure, a substrate having an etchable layer containing a Group 6 element metal is, in one or more embodiments, a substrate having a metal layer containing a Group 6 element metal. Examples of substrates include, in one or more embodiments, at least one substrate selected from semiconductor wafers, liquid crystal display substrates, plasma display substrates, FED (Field Emission Display) substrates, optical disc substrates, magnetic disc substrates, magneto-optical disc substrates, photomask substrates, ceramic substrates, and solar cell substrates.

[0014] [Step 1: Etching process] Step 1 in the substrate manufacturing method of this disclosure is an etching step in which the layer to be etched of a substrate having an etchable layer containing a Group 6 element metal is etched with a composition (etching solution) containing phosphoric acid, nitric acid, and an organic acid.

[0015] Step 1 is, in one or more embodiments, a step of bringing an etching solution into contact with a substrate having an etchable layer containing a Group 6 element metal. Examples of etching methods in step 1, or methods for contacting the substrate having the layer to be etched with an etching solution, include immersion etching and single-wafer etching.

[0016] In one or more embodiments, when the etched layer is a tungsten film, the temperature of the etching solution in Step 1 (etching temperature) is preferably 0°C or higher, more preferably 50°C or higher, still more preferably 70°C or higher, and preferably 150°C or lower, more preferably 130°C or lower, still more preferably 110°C or lower, from the viewpoint of uniform etching of the etched layer. More specifically, in one or more embodiments, when the etched layer is a tungsten film, the etching temperature is preferably 0°C or higher and 150°C or lower, more preferably 50°C or higher and 130°C or lower, still more preferably 70°C or higher and 110°C or lower. In one or more embodiments, when the etched layer is a molybdenum film, the temperature of the etching solution in Step 1 (etching temperature) is preferably 0°C or higher, more preferably 15°C or higher, still more preferably 20°C or higher, and preferably 80°C or lower, more preferably 65°C or lower, still more preferably 50°C or lower, from the viewpoint of uniform etching of the etched layer. More specifically, in one or more embodiments, when the etched layer is a molybdenum film, the etching temperature is preferably 0°C or higher and 80°C or lower, more preferably 15°C or higher and 65°C or lower, still more preferably 20°C or higher and 50°C or lower.<

[0017] In Step 1, the etching time, or the time for bringing the etching solution into contact with the substrate having the etched layer, can be set, for example, to 1 minute or longer and 180 minutes or shorter.

[0018] [Composition (etching solution) used in Step 1] In one or more embodiments, the composition (etching solution) used in Step 1 is a composition further containing water. In one or more embodiments, the composition (etching solution) used in Step 1 is a composition further containing a nitrogen-containing basic compound. Hereinafter, each component contained in the composition used in Step 1 (hereinafter also referred to as "etching solution used in Step 1") will be described. ​

[0019] (Organic acid in the etching solution) Examples of the organic acid contained in the etching solution used in Step 1 include at least one selected from formic acid, acetic acid, methoxyacetic acid, ethoxyacetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, fumaric acid, phthalic acid, trimellitic acid, hydroxyacetic acid, lactic acid, salicylic acid, malic acid, tartaric acid, citric acid, aspartic acid, and glutamic acid. From the viewpoint of uniform etching of the etched layer, as the organic acid, a monovalent organic acid having 1 to 10 carbon atoms is preferable, a monovalent carboxylic acid having 1 to 10 carbon atoms is more preferable, and those containing acetic acid are still more preferable. The organic acid may be used alone or in combination of two or more.

[0020] From the viewpoint of uniform etching of the etched layer, the blending amount of the organic acid in the etching solution used in Step 1 is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and from the same viewpoint, it is preferably 95% by mass or less, more preferably 70% by mass or less, still more preferably 50% by mass or less. More specifically, the blending amount of the organic acid in the etching solution used in Step 1 is preferably 2% by mass or more and 95% by mass or less, more preferably 3% by mass or more and 70% by mass or less, still more preferably 5% by mass or more and 50% by mass or less. When the organic acid is a combination of two or more, the blending amount of the organic acid is the total blending amount thereof. When the organic acid contains acetic acid, from the viewpoint of uniform etching of the etched layer, the blending amount of acetic acid in the etching solution used in Step 1 is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and from the same viewpoint, it is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 88% by mass or less, still more preferably 80% by mass or more, still more preferably 70% by mass or less, still more preferably 50% by mass or less, still more preferably 10% by mass or less.

[0021] (Phosphoric acid in the etching solution) From the viewpoint of uniform etching of the layer to be etched, the amount of phosphoric acid in the etching solution used in step 1 is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 40% by mass or more. From the same viewpoint, it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. More specifically, the amount of phosphoric acid in the etching solution used in step 1 is preferably 5% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 85% by mass or less, and even more preferably 40% by mass or more and 80% by mass or less.

[0022] (Nitric acid in etching solution) From the viewpoint of improving the etching rate, the amount of nitric acid in the etching solution used in step 1 is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. From the viewpoint of uniform etching of the layer to be etched, it is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. More specifically, the amount of nitric acid in the etching solution used in step 1 is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less.

[0023] The total amount of phosphoric acid, nitric acid, and organic acid in the etching solution used in step 1 is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, and from the viewpoint of uniform etching of the layer to be etched, it is preferably 100% by mass or less, more preferably 99.9% by mass or less, even more preferably 99% by mass or less, and even more preferably 98% by mass or less. The total amount of phosphoric acid, nitric acid, and organic acid in the etching solution used in step 1 is preferably 70% by mass or more and 100% by mass or less, more preferably 75% by mass or more and 99.9% by mass or less, and even more preferably 80% by mass or more and 99% by mass or less, or 80% by mass or more and 98% by mass or less.

[0024] In one or more embodiments, the acid contained in the etching solution used in step 1 is an acid containing phosphoric acid, nitric acid, and an organic acid. From the viewpoint of improving the etching rate, it is preferably an acid containing phosphoric acid, nitric acid, and acetic acid, and more preferably a mixed acid consisting of phosphoric acid, nitric acid, and acetic acid. In this disclosure, "mixed acid" means, in one or more embodiments, a mixed acid containing an organic acid; in other embodiments, a mixed acid containing phosphoric acid, nitric acid and an organic acid; in yet another embodiment, a mixed acid containing phosphoric acid, nitric acid and acetic acid; and in yet another embodiment, a mixed acid consisting of phosphoric acid, nitric acid and acetic acid.

[0025] (Nitrogen-containing basic compounds in etching solutions) In one or more embodiments, the etching solution used in step 1 may further contain a nitrogen-containing basic compound. If the etching solution used in step 1 contains a nitrogen-containing basic compound, precipitation of water-insoluble materials becomes particularly pronounced when water washing is performed after step 1. This is thought to be because the nitrogen-containing basic compound readily forms composites with the metal that dissolves from the etched layer. In the substrate manufacturing method of this disclosure, by performing steps 1 and 2 consecutively, even if the etching solution contains a nitrogen-containing basic compound, the composite formed in step 1 is dissolved by the acid with a pKa of 4 or less used in step 2, and the precipitation of water-insoluble materials can be further suppressed. The nitrogen-containing basic compound contained in the etching solution used in step 1 is, in one or more embodiments, at least one compound selected from compounds having ethyleneimine as a repeating unit, compounds having repeating units derived from allylamine, and compounds having repeating units derived from diallylamine. The nitrogen-containing basic compound may be one type or a combination of two or more types. Examples of compounds that use ethyleneimine as a repeating unit include polyethyleneimine (PEI). Examples of compounds having repeating units derived from allylamine include allylamine hydrochloride polymers and allylamine polymers. Examples of compounds having repeating units derived from diallylamine include diallylamine polymers and diallylamine / sulfur dioxide copolymers. Among these, the nitrogen-containing basic compound included in the etching solution used in step 1 is preferably a compound with ethyleneimine as a repeating unit, and more preferably polyethyleneimine (PEI), from the viewpoint of uniform etching of the layer to be etched.

[0026] In one or more embodiments, the number-average molecular weight of a compound with ethyleneimine as a repeating unit is preferably 300 or more, more preferably 600 or more, and even more preferably 1,200 or more, from the viewpoint of uniform etching of the layer to be etched, and from the viewpoint of viscosity, it is preferably 100,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. More specifically, the number-average molecular weight of a compound with ethyleneimine as a repeating unit is preferably 300 or more and 100,000 or less, more preferably 600 or more and 10,000 or less, and even more preferably 1,200 or more and 5,000 or less. In one or more embodiments, the weight-average molecular weight of the compound having repeating units derived from allylamine is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and preferably 50,000 or less, more preferably 10,000 or less, and even more preferably 7,000 or less, from the viewpoint of uniform etching of the layer to be etched. More specifically, the weight-average molecular weight of the compound having repeating units derived from allylamine is preferably 1,000 or more and 50,000 or less, more preferably 2,000 or more and 10,000 or less, and even more preferably 3,000 or more and 7,000 or less. In one or more embodiments, the weight average molecular weight of the compound having a repeating unit derived from diallylamine is preferably 1,000 or more, more preferably 2,000 or more, still more preferably 3,000 or more, and preferably 50,000 or less, more preferably 10,000 or less, still more preferably 7,000 or less, from the viewpoint of uniform etching of the etched layer. More specifically, the weight average molecular weight of the compound having a repeating unit derived from diallylamine is preferably 1,000 or more and 50,000 or less, more preferably 2,000 or more and 10,000 or less, still more preferably 3,000 or more and 7,000 or less.

[0027] Examples of the method for measuring the number average molecular weight or weight average molecular weight of the nitrogen-containing basic compound in the present disclosure are shown below. <GPC Conditions> Sample solution: Adjusted to a concentration of 0.1 wt% Apparatus / Detector: HLC-8320GPC (Integrated GPC) manufactured by Tosoh Corporation Column: α-M + α-M (manufactured by Tosoh Corporation) Eluent: 0.15 mol / L Na2SO4, 1% CH3COOH / water Column temperature: 40 °C Flow rate: 1.0 mL / min Sample solution injection volume: 100 μL Standard polymer: Pullulan with known molecular weight (Shodex P-5, P-50, P-200, P-800)

[0028] The amount of nitrogen-containing basic compound in the etching solution used in step 1 is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still preferably 0.1% by mass or more, from the viewpoint of keeping the etching rate below a certain level. Furthermore, from the viewpoint of keeping the etching rate above a certain level, it is preferably 10% by mass or less, more preferably 5% by mass or less, and still preferably 3% by mass or less. More specifically, the amount of nitrogen-containing basic compound in the etching solution used in step 1 is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and still preferably 0.1% by mass or more and 3% by mass or less. When there is a combination of two or more nitrogen-containing basic compounds, the amount of nitrogen-containing basic compounds is the total amount of those compounds.

[0029] In one or more embodiments, the etching solution used in step 1 is preferably a composition containing phosphoric acid, nitric acid, acetic acid, and polyethyleneimine. The mass ratio (phosphoric acid / acetic acid) of phosphoric acid to acetic acid in the etching solution used in step 1 is preferably 0.5 or more, more preferably 1 or more, even more preferably 5 or more, and preferably 20 or less, more preferably 15 or less, and even more preferably 12 or less. The mass ratio of phosphoric acid to nitric acid (phosphoric acid / nitric acid) in the etching solution used in step 1 is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less. The mass ratio of acetic acid to nitric acid (acetic acid / nitric acid) in the etching solution used in step 1 is preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, and preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less. The mass ratio (phosphoric acid / polyethyleneimine) of phosphoric acid to polyethyleneimine in the etching solution used in step 1 is preferably 40 or more, more preferably 50 or more, even more preferably 60 or more, and preferably 200 or less, more preferably 150 or less, and even more preferably 100 or less. The mass ratio (acetic acid / polyethyleneimine) of acetic acid to polyethyleneimine in the etching solution used in step 1 is preferably 1 or more, more preferably 4 or more, even more preferably 5 or more, and preferably 200 or less, more preferably 100 or less, and even more preferably 10 or less. The mass ratio (nitric acid / polyethyleneimine) of nitric acid to polyethyleneimine in the etching solution used in step 1 is preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, and preferably 30 or less, more preferably 15 or less, and even more preferably 5 or less.

[0030] (Water in the etching solution) In one or more embodiments, the etching solution used in step 1 may further contain water. Examples of water contained in the etching solution used in step 1 include distilled water, deionized water, pure water, and ultrapure water. From the viewpoint of uniform etching of the layer to be etched, the amount of water in the etching solution used in step 1 is preferably 0% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more. From the same viewpoint, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. More specifically, the amount of water in the etching solution used in step 1 is preferably 0% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 7% by mass or more and 20% by mass or less.

[0031] (Other ingredients) The etching solution used in step 1 may further contain other components, to the extent that the effects of this disclosure are not impaired. Examples of other components include inorganic acids other than phosphoric acid and nitric acid, chelating agents, surfactants, solubilizers, preservatives, rust inhibitors, disinfectants, antibacterial agents, antioxidants, and the like. In one or more embodiments, the etching solution used in step 1 may be substantially free of hydrofluoric acid. For example, the content or amount of hydrofluoric acid in the etching solution used in step 1 is preferably less than 0.1% by mass, more preferably 0.01% by mass or less, and even more preferably 0% by mass (i.e., not containing any). In one or more embodiments, the etching solution used in step 1 may substantially contain no hydroxylamine compounds selected from hydroxylamine and hydroxylamine salts. For example, the content or amount of hydroxylamine compounds in the etching solution used in step 1 is preferably less than 0.001% by mass, and more preferably 0% by mass (i.e., not included).

[0032] The etching solution used in step 1 is obtained in one or more embodiments by compounding phosphoric acid, nitric acid, and organic acid with the above-mentioned optional components (nitrogen-containing basic compounds, other components) in a known manner. The order in which the components for preparing (manufacturing) the etching solution are mixed in this disclosure is not particularly limited. The mixing can be carried out using, for example, a propeller-type stirrer, liquid circulation stirring with a pump, a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. In the preparation (manufacturing) of the etching solution, the preferred blending amounts of each component can be the same as the preferred blending amounts of each component in the etching solution used in step 1 described above.

[0033] In this disclosure, "amount of each component of the etching solution" means, in one or more embodiments, the amount of each component in the etching solution at the time of use in step 1, that is, at the time of use when starting the etching process (at the time of use). The amount of each component blended in the etching solution used in step 1 can be considered as the content of each component in the etching solution used in step 1 in one or more embodiments. However, if neutralization is involved, the blended amount and the content may differ.

[0034] The etching solution used in Step 1 may be a so-called one-component type, where all components are pre-mixed and supplied to the market, or a so-called two-component type, where the components are mixed at the time of use. An example of a two-component etching solution is one in which water is separated into a first solution and a second solution, and phosphoric acid, nitric acid, an organic acid, and water are contained in either the first solution or the second solution, or in both, and the first solution and the second solution are mixed at the time of use. After the first solution and the second solution are mixed, they may be diluted with water or an acidic aqueous solution as needed. The first solution and the second solution may each contain the above-mentioned optional components (nitrogen-containing basic compounds, other components) as needed.

[0035] The pH of the etching solution used in step 1 is preferably 1 or less, more preferably 0 or less, even more preferably less than 0, and even more preferably around -1, from the viewpoint of uniform etching of the layer to be etched. The pH of the etching solution used in step 1 can preferably be -5 or higher, more preferably -3 or higher. In this disclosure, the pH of the etching solution is the value at 25°C and can be measured using a pH meter, specifically by the method described in the examples.

[0036] The etching solution used in step 1 may be stored and supplied in a concentrated state, provided that its storage stability is not compromised. This is preferable because it reduces manufacturing and transportation costs. This concentrated solution can then be used in the etching process after being appropriately diluted with water or an acidic aqueous solution as needed. The dilution ratio can be, for example, 3 to 100 times.

[0037] [Step 2: Washing Process] Step 2 in the substrate manufacturing method of this disclosure is a step (cleaning step) in which the substrate obtained in step 1 is cleaned with an acid (rinsing solution) having a pKa of 4 or less.

[0038] Step 2, in one or more embodiments, includes bringing the substrate after Step 1 into contact with a rinsing solution. Examples of cleaning methods in step 2, or methods for bringing the substrate into contact with the rinsing solution after step 1, include immersion cleaning, ultrasonic cleaning, agitation cleaning, spray cleaning, and cleaning using rotation such as a spinner. The above-mentioned cleaning methods may be performed individually or in combination. In step 2, the temperature of the rinse solution may be, for example, between 0°C and 100°C. In step 2, the rinsing time for rinsing with the rinse solution, or the time for the rinse solution to come into contact with the substrate after step 1, can be, for example, 10 seconds or more and 120 minutes or less. In step 2, ultrasonic waves can be irradiated when the rinsing solution comes into contact with the substrate. Examples of ultrasonic irradiation conditions include 20 to 5000 kHz.

[0039] (Acids (rinsing solutions) with a pKa of 4 or less) The pKa of the acid used for washing in step 2 is preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less, from the viewpoint of suppressing the generation of water-insoluble matter. Similarly, it is preferably -12 or higher, more preferably -11 or higher, and even more preferably -10 or higher. More specifically, the pKa of the acid used for washing in step 2 is preferably -12 or higher and 3 or less, more preferably -11 or higher and 2 or less, and even more preferably -10 or higher and 1 or less. In this disclosure, the pKa is pKa1 in one or more embodiments when the acid has multiple pKas.

[0040] In one or more embodiments, the acid with a pKa of 4 or less used in step 2 is preferably at least one of an inorganic acid and an organic acid, from the viewpoint of suppressing the generation of water-insoluble substances. Examples of inorganic acids include at least one selected from hydrofluoric acid (pKa 3.2), hydrochloric acid (pKa -8.0), sulfuric acid (pKa -3.0), and phosphoric acid (pKa 2.2). Examples of organic acids include at least one selected from methanesulfonic acid (pKa -2.6), citric acid (pKa 3.1), tartaric acid (pKa 2.89), and lactic acid (pKa 3.86). In step 2, the acid with a pKa of 4 or less is, in one or more embodiments, preferably, from a similar viewpoint, at least one selected from hydrofluoric acid, hydrochloric acid, sulfuric acid, phosphoric acid, methanesulfonic acid, and citric acid, and more preferably at least one selected from hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid. The acid with a pKa of 4 or less used for washing in step 2 may be one type or a combination of two or more types.

[0041] The acid (rinsing solution) used for cleaning in step 2 is, in one or more embodiments, an aqueous acid solution containing an acid with a pKa of 4 or less in an amount of 0.01% by mass or more and 85% by mass or less. In one or more embodiments, the aqueous acid solution is an aqueous solution obtained by mixing an acid with a pKa of 4 or less with water. Examples of water contained in the aqueous acid solution include distilled water, deionized water, pure water, and ultrapure water. In one or more embodiments, the amount of acid with a pKa of 4 or less in the acidic aqueous solution is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of suppressing the generation of water-insoluble matter, and from the viewpoint of viscosity, preferably 85% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. More specifically, the amount of acid with a pKa of 4 or less in the acidic aqueous solution is preferably 0.01% by mass or more and 85% by mass or less, more preferably 0.1% by mass or more and 70% by mass or less, and even more preferably 1% by mass or more and 60% by mass or less. When there is a combination of two or more acids with a pKa of 4 or less, the amount of acid with a pKa of 4 or less is the total amount of those acids. In one or more embodiments, the amount of acid with a pKa of 4 or less in the acidic aqueous solution can be considered as the content of acid with a pKa of 4 or less in the acidic aqueous solution. If the acid with a pKa of 4 or less in step 2 is phosphoric acid, the amount of phosphoric acid in the acid aqueous solution is preferably 5% by mass or more and 85% by mass or less, from a similar viewpoint, in one or more embodiments.

[0042] In one or more embodiments, the acid (rinsing solution) used in step 2 preferably does not contain any components other than an acid with a pKa of 4 or less and water. The acid (rinsing solution) used in step 2 is, in one or more embodiments, substantially free of nitrogen-containing basic compounds. For example, the amount of nitrogen-containing basic compounds in the acid (rinsing solution) is preferably less than 0.01% by mass, more preferably 0.001% by mass or less, and even more preferably 0% by mass (i.e., not present). The acid (rinsing solution) used in step 2 is, in one or more embodiments, substantially free of nitric acid. For example, the amount of nitric acid in the acid (rinsing solution) is preferably less than 0.5% by mass, more preferably 0.1% by mass or less, and even more preferably 0% by mass (i.e., not present). The acid (rinsing solution) used in step 2 is, in one or more embodiments, substantially free of oxidizing agents. The amount of oxidizing agent in the acid (rinsing solution) used in step 2 is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0% by mass (i.e., not present).

[0043] In step 2, the etching rate of the metal containing Group 6 elemental metals is preferably 10 μm / min or less, more preferably 1 μm / min or less, and even more preferably 0.1 μm / min or less. In step 2, the metal containing Group 6 elemental metals is not etched substantially. Therefore, in one or more embodiments, the acid (rinsing solution) used in step 2 does not substantially etch the metal layer (i.e., the metal layer containing Group 6 elemental metals) that the substrate has after step 1.

[0044] In the substrate manufacturing method of this disclosure, steps 1 and 2 are carried out in succession. Performing the process continuously means, in one or more embodiments, that there is no step of washing the substrate obtained in step 1 with water between step 1 and step 2. Performing the process continuously means, in one or more embodiments, that there is no step of alkaline cleaning the substrate obtained in step 1 between step 1 and step 2.

[0045] In one or more embodiments, the substrate manufacturing method of this disclosure may further include a step (step 3) of washing the substrate after step 2 with water. Step 3, in one or more embodiments, includes bringing the substrate after Step 2 into contact with water. Methods for bringing the substrate after Step 2 into contact with water include, for example, immersing the substrate in a tank of water, or spraying water onto the substrate to bring it into contact. The contact time between the substrate and water is preferably, for example, 10 seconds to 120 minutes. Step 3, in one or more embodiments, includes drying the substrate after water washing (the substrate after contact with water). Examples of drying methods include air blow drying.

[0046] [Method for processing circuit boards] This disclosure relates to a substrate processing method (hereinafter also referred to as "the substrate processing method of this disclosure") in one embodiment, comprising a step of cleaning the substrate to be processed with an acid having a pKa of 4 or less (cleaning step), wherein the substrate to be processed is a substrate having a metal layer containing a Group 6 elemental metal, which has been etched with a composition containing phosphoric acid, nitric acid, and an organic acid, and the cleaning step is performed immediately after etching.

[0047] In this disclosure, the substrate processing method is, in one or more embodiments, a method for cleaning a substrate. That is, the substrate processing method of this disclosure is, in one or more embodiments, a method for cleaning a substrate to be processed, which includes a step (cleaning step) of cleaning the substrate with an acid (rinsing solution) having a pKa of 4 or less. In one or more embodiments, the cleaning step in the substrate processing method of this disclosure corresponds to step 2 in the substrate manufacturing method of this disclosure described above. In one or more embodiments, the cleaning method and cleaning conditions in the cleaning step of the substrate processing method of this disclosure may be the same as the cleaning method and cleaning conditions in step 2 of the substrate manufacturing method of this disclosure described above.

[0048] In the substrate processing method of this disclosure, the substrate to be processed is, in one or more embodiments, a substrate having a metal layer containing a Group 6 elemental metal, after being etched with a composition (etching solution) containing phosphoric acid, nitric acid, and an organic acid. In one or more embodiments, the substrate to be processed is the substrate after step 1 of the substrate manufacturing method of this disclosure described above.

[0049] In the substrate processing method of this disclosure, the cleaning step is performed immediately after etching the substrate having a metal layer containing the Group 6 element metal. In one or more embodiments of the substrate processing method of this disclosure, the process does not include a step of washing the substrate to be processed with water after etching and before the cleaning step. In one or more embodiments of the substrate processing method of this disclosure, the step of alkaline cleaning the substrate to be processed after etching and before the cleaning step is not included.

[0050] In one or more embodiments, the substrate processing method of the present disclosure may further include a step of washing the substrate with water after the cleaning step (water washing step). In one or more embodiments, the water washing step includes bringing the substrate after the washing step (the substrate after washing with an acid with a pKa of 4 or less) into contact with water. Examples of methods for bringing the substrate after the washing step into contact with water include immersing the substrate in a tank of water, or spraying water onto the substrate to bring it into contact. The contact time between the substrate and water is preferably, for example, 10 seconds to 120 minutes. In one or more embodiments, the water washing step includes drying the substrate after water washing (the substrate after contact with water). Examples of drying methods include air blow drying.

[0051] The substrate processing method of this disclosure can be suitably used in the production of semiconductor wafers in one or more embodiments. The substrate manufacturing method and substrate processing method of the present disclosure can be suitably used in one or more embodiments to produce patterns having a three-dimensional structure. This makes it possible to obtain advanced devices such as high-capacity memory. The substrate manufacturing method and substrate processing method of the present disclosure can be used in one or more embodiments in the manufacturing process of semiconductor memories such as electrode wiring used in electronic devices, particularly semiconductor devices such as liquid crystal display devices, and non-volatile memories including 3D-NAND flash memory. The substrate manufacturing method and substrate processing method of the present disclosure can be suitably used in one or more embodiments for forming single-layer metal wiring and for manufacturing multilayer metal wiring. This makes it possible to give the cross-sectional shape of the wiring sides a good forward taper shape. [Examples]

[0052] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited in any way by these examples.

[0053] 1. Preparation of etching solution (Examples 1-11, Comparative Examples 1-3) As shown in Table 1, a mixed acid (phosphoric acid / acetic acid / nitric acid, mass ratio in etching solution: 75 / 7 / 3), a nitrogen-containing basic compound (polyethyleneimine), and water were mixed, and then molybdenum (Mo) powder was added. This mixture was then thoroughly dissolved at 60°C until it became transparent to obtain the etching solutions (pH: -1) of Examples 1-11 and Comparative Examples 1-3. Table 1 shows the proportions (mass %) and effective content of each component in the etching solutions prepared as described above. The amount of water is the remainder after subtracting the mixed acid and nitrogen-containing basic compound from the total amount of etching solution (100 mass%). Note that the mass ratio of the mixed acid is calculated on a mass basis, and the amount of water includes the amount of water contained in the acidic aqueous solution, etc. The amount of Mo dissolved in the etching solution (ppm) is shown in Table 1. Note that 1 ppm is equal to 0.0001 mass%. The etching solution with added molybdenum powder is intended to be the etching solution after it has been used to etch the molybdenum-containing layer (the etching solution after step 1).

[0054] The following components were used to prepare the etching solution. Phosphoric acid [manufactured by Phosphorus Chemical Industry Co., Ltd., concentration 85%] Nitric acid [Fujifilm Wako Pure Chemical Industries, Ltd., 70% concentration] Acetic acid [Fujifilm Wako Pure Chemical Industries, Ltd., 100% concentration] Polyethyleneimine (PEI) [Number average molecular weight 1,800, "Epomin SP-018" manufactured by Nippon Shokubai Co., Ltd.] Water [Ultrapure water produced using a continuous pure water production system (PureConti PC-2000VRL model) and subsystem (MacAce KC-05H model) manufactured by Kurita Water Industries Ltd.] Molybdenum powder ["Mo-3K" manufactured by Nippon Shinkinzoku Co., Ltd.]

[0055] 2. Preparation of Rinse Solution (Examples 1-11, Comparative Examples 1-3) (Examples 1-11, Comparative Examples 2-3) For Examples 1-11 and Comparative Examples 2-3, acidic aqueous solutions were obtained by combining the acids shown in Table 1 with water. The amount of acid (mass %) in the acidic aqueous solutions is as shown in Table 1. (Comparative Example 1) In Comparative Example 1, water (100% by mass) was used as the rinsing solution. The rinsing solutions in Examples 1-11 and Comparative Examples 1-3 are intended to be rinsing solutions used for cleaning the substrate after etching (acidic aqueous solution or water used for cleaning in step 2).

[0056] The following ingredients were used to prepare the rinse solution. Phosphoric acid [manufactured by Phosphorus Chemical Industry Co., Ltd., concentration 85%] Hydrochloric acid [Fujifilm Wako Pure Chemical Industries, Ltd., 35% concentration] Sulfuric acid [Fujifilm Wako Pure Chemical Industries, Ltd., concentration 96%] Hydrofluoric acid [Sigma-Aldrich, 48% concentration] Methanesulfonic acid [Fujifilm Wako Pure Chemical Corporation, concentration 98%] Citric acid [Fuso Chemical Industries Co., Ltd., 50% concentration] Acetic acid [Fujifilm Wako Pure Chemical Industries, Ltd., 100% concentration] Ammonia [29% by mass aqueous ammonia, manufactured by Kanto Chemical Co., Ltd.] Water [Ultrapure water produced using a continuous pure water production system (PureConti PC-2000VRL model) and subsystem (MacAce KC-05H model) manufactured by Kurita Water Industries Ltd.]

[0057] 3. Method for measuring the pH of the etching solution The pH value of the etching solution at 25°C was measured using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value was obtained one minute after immersing the pH meter's electrode in the etching solution.

[0058] 4. Evaluation [Evaluation of the presence or absence of water-insoluble precipitation] 0.2 g of etching solution containing Mo and 1.8 g of acidic aqueous solution were placed in a 9 mL glass bottle and mixed at room temperature (25°C). The mixing ratio of the etching solution to the rinsing solution, i.e., the amount of etching solution / the amount of rinsing solution, is 10% by mass / 90% by mass, as shown in Table 1. Ten seconds after mixing, the presence or absence of precipitates (water-insoluble substances) was visually checked. The results regarding the presence or absence of precipitates are shown in Table 1. In Table 1, "1" is indicated if precipitate formation was confirmed, and "0" is indicated if precipitate formation was not confirmed.

[0059] [Table 1]

[0060] As shown in Table 1, in all of Examples 1 to 11, where an aqueous solution of an acid with a pKa of 4 or less was used as the rinsing solution in Step 2, the generation of water-insoluble substances was suppressed. On the other hand, in Comparative Example 1, where water was used as the rinsing solution in Step 2; Comparative Example 2, where an acid with a pKa of 4.6 was used as the rinsing solution in Step 2; and Comparative Example 3, where an acid with a pKa of 9.3 was used as the rinsing solution in Step 2, water-insoluble substances were generated. Based on these findings, it was concluded that using an acid with a pKa of 4 or less for rinsing substrates etched with a composition containing phosphoric acid, nitric acid, and organic acids can suppress the generation of water-insoluble substances and reduce the amount of residue adhering to the substrate.

[0061] Furthermore, the following evaluations were performed on Example 2 and Comparative Example 1. [Evaluation of residue after etching] (Example 2) A wafer with molybdenum layers measuring 1 cm vertically and 2 cm horizontally was immersed in the etching solution of Example 2 (phosphoric acid / acetic acid / nitric acid / polyethyleneimine / water = 75 / 7 / 3 / 1 / 14 (mass ratio), Mo dissolution amount 5000 ppm), and etching was performed at 30°C for 15 minutes. After etching, the wafer was continuously immersed in the rinsing solution of Example 2 (5 mass% phosphoric acid aqueous solution) for 5 minutes, then washed with water, and dried by air blowing to obtain wafer 1. (Comparative Example 1) A wafer with molybdenum layers measuring 1 cm vertically and 2 cm horizontally was immersed in the etching solution of Comparative Example 1 (phosphoric acid / acetic acid / nitric acid / polyethyleneimine / water = 75 / 7 / 3 / 1 / 14 (mass ratio), Mo dissolution amount 5000 ppm), and etching was performed at 30°C for 15 minutes. After etching, wafer 2 was obtained by washing with the rinsing solution (water) of Comparative Example 1, i.e., washing with water only. The surfaces of the obtained wafers 1 and 2 were observed using a scanning electron microscope (Hitachi High-Technologies Corporation S-4800). As a result, residue was observed on wafer 2, which was washed only with water after etching, whereas no residue was observed on wafer 1, which was washed by a method including immersion in the 5% by mass phosphoric acid aqueous solution after etching. From the above, it was found that using an acid with a pKa of 4 or less for rinsing a substrate etched with a composition containing phosphoric acid, nitric acid, and organic acid can suppress the generation of water-insoluble substances and reduce the amount of residue adhering to the substrate. [Industrial applicability]

[0062] This disclosure provides a substrate manufacturing method that can suppress the generation of water-insoluble substances and reduce residue adhering to the substrate, and is useful in the manufacturing of high-capacity semiconductor memory.

Claims

1. A method for manufacturing a substrate, comprising the following steps 1 and 2, wherein steps 1 and 2 are performed sequentially. Step 1: A step of etching the etchable layer of a substrate having an etchable layer containing a Group 6 element metal with a composition containing phosphoric acid, nitric acid, and an organic acid. Step 2: A step in which the substrate obtained in Step 1 is washed with an acid with a pKa of 4 or less.

2. The manufacturing method according to claim 1, wherein the composition used in step 1 is a composition further containing water.

3. The manufacturing method according to claim 1 or 2, wherein the composition used in step 1 is a composition further comprising a nitrogen-containing basic compound.

4. The manufacturing method according to claim 1, wherein the acid with a pKa of 4 or less in step 2 is at least one of an inorganic acid and an organic acid.

5. The manufacturing method according to claim 4, wherein the acid with a pKa of 4 or less in step 2 is at least one selected from hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

6. The manufacturing method according to claim 1, wherein the organic acid contained in the composition used in step 1 is a monovalent carboxylic acid having 1 to 10 carbon atoms.

7. The manufacturing method according to claim 1, wherein the amount of organic acid in the composition used in step 1 is 2% by mass or more and 95% by mass or less.

8. The manufacturing method according to claim 1, wherein the amount of phosphoric acid in the composition used in step 1 is 5% by mass or more and 90% by mass or less.

9. The manufacturing method according to claim 1, wherein the amount of nitric acid in the composition used in step 1 is 0.5% by mass or more and 20% by mass or less.

10. The manufacturing method according to claim 1 or 2, wherein the acid used for washing in step 2 is an aqueous acid solution in which the amount of an acid with a pKa of 4 or less is 0.01% by mass or more and 85% by mass or less.

11. The manufacturing method according to claim 3, wherein the nitrogen-containing basic compound contained in the composition used in step 1 is polyethyleneimine.

12. The manufacturing method according to claim 1 or 2, wherein the Group 6 elemental metal is at least one selected from tungsten and molybdenum.

13. The manufacturing method according to claim 1 or 2, wherein the process of performing step 1 and step 2 consecutively does not include a step of washing the substrate obtained in step 1 with water between step 1 and step 2.

14. A method for processing a substrate, The process includes a step of cleaning the substrate to be treated with an acid having a pKa of 4 or less (cleaning step), The substrate to be treated is a substrate having a metal layer containing a Group 6 elemental metal, which has been etched with a composition containing phosphoric acid, nitric acid, and an organic acid. A substrate processing method wherein the cleaning step is performed immediately after etching a substrate having a metal layer containing the Group 6 element metal.

15. The substrate processing method according to claim 14, wherein the composition further comprises water.

16. The substrate processing method according to claim 15, wherein the composition further comprises a nitrogen-containing basic compound.

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