Cleaning composition for silicon carbide substrate

Abstract

Provided is a manganese-contaminated cleaning composition for a silicon carbide substrate that has high stability and is capable of transporting a product in a solution form. A cleaning solution composition for cleaning a silicon carbide substrate polished by a manganese-containing compound abrasive or a silicon carbide substrate etched by a manganese-containing compound etchant comprises a reducing agent, a pH adjusting agent and water, and has a pH value of less than 5, the reducing agent is one or more selected from the group consisting of a six-membered ring compound in which two or more hydroxyl groups are directly bonded to a ring, glyoxylic acid and diethyl hydroxylamine.

Description

Technical Field

[0001] The present invention relates to a cleaning composition for a silicon carbide substrate and a cleaning method for a silicon carbide substrate. Background Art

[0002] Compared with silicon, the current mainstream semiconductor material, silicon carbide (SiC) has excellent physical properties such as wide bandgap, high dielectric breakdown field strength and high thermal conductivity. Therefore, it is expected to become a semiconductor material for power devices to achieve high power control and energy saving.

[0003] Device manufacturing processes typically include a polishing process to flatten the substrate and an etching process to dissolve away layers of damage caused by processing. However, due to the high hardness of silicon carbide, polishing with silica slurries or etching with strong acids such as nitric acid and fluorine, typically used in silicon substrate processing, is nearly impossible and requires long processing times. To address this, methods have been proposed that use permanganate ions as an oxidizing agent in the slurry or etching solution, or that use manganese oxide as the abrasive in the slurry. However, these methods leave high concentrations of manganese contaminants in the silicon carbide after polishing or etching.

[0004] Manganese oxides used as abrasives include MnO2 and Mn3O4, but trivalent and tetravalent manganese compounds are insoluble. It is speculated that high manganese oxides added to the slurry or etching solution will form insoluble manganese compounds. Once these insoluble manganese compounds adhere to the substrate, they are difficult to clean.

[0005] RCA cleaning is widely used for cleaning silicon carbide. It is basically a combination of the following cleaning methods: SC-1 cleaning (Standard Clean 1) consisting of ammonia water and hydrogen peroxide water for the purpose of removing particles, SC-2 cleaning (Standard Clean 2) consisting of hydrochloric acid and hydrogen peroxide water for the purpose of removing metal impurities, and hydrofluoric acid cleaning. As a cleaning method other than RCA cleaning, Patent Document 1 proposes a cleaning agent having a pH of 6 or less containing at least one of ascorbic acid and isoascorbic acid. Patent Document 2 proposes a method for cleaning a semiconductor substrate comprising a reducing agent such as ascorbic acid and an acid. Prior art literature Patent Literature

[0006] Patent Document 1: International Publication No. 2013 / 088928 Patent Document 2: Japanese Patent Application Laid-Open No. 11-251280 Summary of the Invention Problems to be solved by the present invention

[0007] The RCA cleaning method widely used for silicon carbide cleaning has the following problems: since it uses highly concentrated strong acid and alkaline cleaning solutions at high temperatures, and uses highly concentrated, highly toxic fluoric acid, it places a heavy burden on safety and the environment. Patent documents 1 and 2 propose cleaning agents containing ascorbic acid or isoascorbic acid as reducing agents. However, since ascorbic acid and isoascorbic acid, which have strong reducing power, are easily oxidized and decomposed in solution, their content decreases rapidly, and therefore the cleaning agent products cannot be transported in the form of solutions. Therefore, at the user's site, ascorbic acid or isoascorbic acid, which is transported in solid form, must be formulated into a cleaning solution, which requires the introduction of cleaning solution preparation equipment and filtration equipment, etc., resulting in increased working time and costs.

[0008] An object of the present invention is to provide a cleaning liquid composition for cleaning manganese contamination on a silicon carbide substrate, wherein the cleaning liquid composition has excellent safety and stability and can be transported in the form of a solution. Means used to solve problems

[0009] During in-depth research conducted to solve the above-mentioned problems, the present inventors discovered that a reducing agent selected from the group consisting of six-membered ring compounds with two or more hydroxyl groups directly bonded to the ring, glyoxylic acid, and diethylhydroxylamine can effectively remove manganese compounds on silicon carbide substrates under acidic conditions. After further research, the present invention was finally completed.

[0010] That is, the present invention relates to the following contents. [1] A cleaning liquid composition for cleaning a silicon carbide substrate polished with a manganese compound-containing abrasive or etched with a manganese compound-containing etching solution, characterized in that it contains a reducing agent, a pH adjuster and water, and has a pH value of less than 5, wherein the reducing agent is one or more selected from the following group: a six-membered ring compound in which two or more hydroxyl groups are directly bonded to the ring, glyoxylic acid and diethylhydroxylamine, and the cleaning liquid composition. [2] The composition according to [1], characterized in that: It comprises a six-membered ring compound represented by the following formula (1) in which two or more hydroxyl groups are directly bonded to the ring Chemical formula 1 In the formula, R1-R6 are each independently H, OH, COOH, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, wherein at least two of R1-R6 are OH.

[0011] [3] The cleaning liquid composition according to [1] or [2], characterized in that it contains one or more six-membered ring compounds in which two or more hydroxyl groups are directly bonded to the ring selected from the following group: gallic acid, catechol, resorcinol, hydroquinone, pyrogallol and methylcatechol. [4] The cleaning liquid composition according to any one of [1] to [3], characterized in that the pH adjuster is an inorganic acid or an organic acid. [5] The cleaning liquid composition according to any one of [1] to [4], characterized in that the pH adjuster is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, oxalic acid, malonic acid, succinic acid, malic acid, tartaric acid and citric acid.

[0012] [6] The cleaning liquid composition according to any one of [1] to [5], characterized in that it also contains one or more polysulfonic acid compounds as surfactants. [7] The cleaning liquid composition according to any one of [1] to [6], wherein the concentration of the reducing agent is greater than or equal to 0.001 mass percent and less than or equal to 1 mass percent. [8] A stock solution composition for a cleaning liquid composition as described in any one of [1] to [7], characterized in that it is used to obtain the cleaning liquid composition by diluting it 10 to 1000 times. [9] A method for cleaning a silicon carbide substrate, characterized in that it comprises the following steps: bringing the cleaning liquid composition described in any one of [1] to [7] into contact with a silicon carbide substrate polished with a manganese compound-containing abrasive, or a silicon carbide substrate etched with a manganese compound-containing composition. Effects of the Invention

[0013] The cleaning liquid composition of the present invention safely and easily removes manganese compounds from silicon carbide substrates by using a reducing agent selected from the group consisting of six-membered ring compounds having two or more hydroxyl groups directly bonded to the ring, glyoxylic acid, and diethylhydroxylamine under acidic conditions. While the mechanism is not fully understood, it is believed that the reducing agent used in the present invention stably acts on insoluble manganese compounds under acidic conditions, reducing trivalent and tetravalent insoluble manganese compounds to highly soluble divalent manganese compounds, which then dissolve in the cleaning composition, thereby removing the manganese compounds.

[0014] The cleaning liquid composition of the present invention contains no highly toxic components, eliminating the need for a cleaning process involving multiple cleaning solutions, as is the case with RCA cleaning. Furthermore, since there are no concerns about oxidative decomposition of reducing agents, the cleaning liquid composition of the present invention can be transported in solution form, eliminating the need for pre-prepared cleaning solutions. Consequently, the cleaning liquid composition of the present invention eliminates the need for individual user-provided equipment and the hassle of pre-preparation, significantly reducing the manufacturing cost of silicon carbide devices. DETAILED DESCRIPTION

[0015] Hereinafter, preferred embodiments of the cleaning composition for a silicon carbide substrate and the cleaning method for a silicon carbide substrate of the present invention will be described in detail. The cleaning liquid composition of the present invention is used for cleaning a silicon carbide substrate polished by a manganese compound-containing abrasive or a silicon carbide substrate etched by a manganese compound-containing etching solution.

[0016] The cleaning composition of the present invention can remove manganese contamination remaining on a silicon carbide substrate treated with a manganese compound-containing abrasive and an etching solution. The silicon carbide substrate is not particularly limited and may have a silicon carbide layer on its surface. The silicon carbide may be single crystal silicon carbide or epitaxial silicon carbide.

[0017] The manganese compound contained in the polishing agent and the etching solution is a manganese compound generally used in polishing agents and etching solutions, and includes, for example, manganese dioxide, manganese trioxide, permanganate, and the like. In addition to the manganese compound, the manganese compound remaining on the silicon carbide substrate may further include a manganese compound in the form of ions, such as manganese ions and permanganate ions.

[0018] The reducing agent included in the cleaning liquid composition of the present invention can be any reducing agent capable of altering the valence state of the insoluble manganese compound. Preferred reducing agents include six-membered ring compounds having two or more hydroxyl groups directly bonded to the ring, glyoxylic acid, and diethylhydroxylamine, from the perspective of being able to stably and effectively reduce the insoluble manganese compound in acidic conditions. The reducing agent can be used alone or in combination of two or more.

[0019] The six-membered ring compound in which two or more hydroxyl groups are directly bonded to the ring is not particularly limited as long as it can effectively reduce the insoluble manganese compound, but may be, for example, a compound represented by the following formula (1). Chemical formula 2 In the formula, R1-R6 are each independently H, OH, COOH, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, wherein at least two, preferably two or three, of R1-R6 are OH.

[0020] Six-membered ring compounds having two or more hydroxyl groups directly bonded to the ring act stably as reducing agents on insoluble manganese compounds under acidic conditions, reducing them. Examples of six-membered ring compounds having two or more hydroxyl groups directly bonded to the ring include gallic acid, catechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-trihydroxybenzene, methylcatechol, methylhydroquinone, and tert-butylhydroquinone, with gallic acid and pyrogallol being particularly preferred.

[0021] The concentration of the reducing agent is not particularly limited, but is, for example, 0.0001 mass percent or greater, more preferably 0.001 mass percent or greater. This allows the manganese compound to be fully and effectively reduced from trivalent or tetravalent to divalent. Furthermore, the upper limit of the reducing agent concentration is not particularly limited, but is, for example, 10 mass percent or less, more preferably 1 mass percent or less. In one embodiment of the present invention, the concentration of the reducing agent is 0.0001 mass percent or greater and 10 mass percent or less. In a preferred embodiment, the concentration of the reducing agent is 0.001 mass percent or greater and 1 mass percent or less.

[0022] The pH adjuster contained in the cleaning liquid composition of the present invention is not particularly limited as long as it can adjust the pH of the cleaning composition to an acidic state. However, the pH adjuster, in combination with the reducing agent, has the function of separating the manganese compound remaining on the silicon carbide substrate from the substrate surface and dissolving it in the cleaning composition. Such pH adjusters include, for example, inorganic acids and organic acids, which can be used alone or in combination of two or more.

[0023] Inorganic acids include hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and perchloric acid. Preferably, the cleaning liquid composition of the present invention comprises one or more inorganic acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0024] Organic acids include organic sulfonic acids, such as methanesulfonic acid, ethanesulfonic acid, etc.; aliphatic monocarboxylic acids, such as formic acid, acetic acid, propionic acid, etc.; dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, etc.; oxypolycarboxylic acids, such as tartaric acid, malic acid, citric acid, etc. Preferably, the cleaning liquid composition of the present invention includes one or more organic acids selected from the following group: methanesulfonic acid, oxalic acid, malonic acid, succinic acid, malic acid, tartaric acid and citric acid.

[0025] In a preferred embodiment, the cleaning liquid composition of the present invention comprises at least one pH adjuster selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, oxalic acid, malonic acid, succinic acid, malic acid, tartaric acid and citric acid.

[0026] The pH of the cleaning liquid composition of the present invention is preferably acidic, preferably less than 5, more preferably 4 or less, and even more preferably 3 or less. This allows the manganese compound on the surface of the silicon carbide substrate to be properly dissolved in the cleaning liquid composition, thereby removing the manganese compound on the surface of the silicon carbide substrate. If the pH is 5 or higher, the solubility is reduced, and the removal efficiency is reduced.

[0027] The concentration of the pH adjuster is not particularly limited as long as it is an amount required to adjust the pH to an acidic state, and is, for example, 0.0001 to 10 mass percent, preferably 0.001 to 1.0 mass percent, and particularly preferably 0.01 to 1.0 mass percent. If the concentration exceeds this range, there is a risk of corrosion of the equipment.

[0028] Furthermore, to improve particle removal, the cleaning liquid composition of the present invention may further include a surfactant. The type of surfactant may be appropriately selected, without limitation, but is preferably a polysulfonic acid compound. Polysulfonic acid compounds include, for example, naphthalenesulfonic acid formaldehyde condensates, polystyrenesulfonic acid, ligninsulfonic acid, and salts thereof. In a preferred embodiment, the cleaning liquid composition of the present invention includes one or more polysulfonic acid compounds.

[0029] The concentration of the surfactant in the cleaning liquid composition of the present invention is not particularly limited, but is, for example, 0.0001 to 10 mass percent, preferably 0.001 to 1.0 mass percent, and particularly preferably 0.001 to 0.1 mass percent. If the concentration exceeds this range, the effect of improving particle removal performance is not enhanced. Therefore, using the surfactant within this range is economical.

[0030] Furthermore, the cleaning liquid composition of the present invention generally includes a solvent. The solvent is not particularly limited, but water is generally used. However, the cleaning liquid composition of the present invention may include an organic solvent as the solvent.

[0031] Such organic solvents include various organic solvents that can be mixed with water, for example, alcohol solvents, ether solvents, ketone solvents, etc., of which one type can be used alone or two or more types can be used in combination.

[0032] Examples of the alcohol solvent include aliphatic alcohol solvents such as methanol, ethanol, and propanol; glycol solvents such as ethylene glycol; and other polyols such as glycerol.

[0033] The concentration of water in the cleaning liquid composition of the present invention is not particularly limited, but is, for example, 10 to 99.99 mass percent, preferably 50 to 99.99 mass percent, and particularly preferably 80 to 99.99 mass percent. The concentration of the organic solvent in the present invention is not particularly limited, but is, for example, 0.0001 to 20 mass percent, preferably 0.001 to 10 mass percent, and particularly preferably 0.01 to 1 mass percent.

[0034] The cleaning liquid composition of the present invention preferably uses the above-mentioned concentrations of each component. However, since a high-concentration product with a concentration of 10 to 1000 times the concentration of each component is also stable, the high-concentration product can be used for storage, transportation, etc., and the high-concentration product can also be diluted before use. Therefore, the present invention also relates to a stock solution composition for the cleaning liquid composition of the present invention, wherein the cleaning liquid composition of the present invention is obtained by diluting the stock solution composition 10 to 1000 times. When the stock solution composition is diluted for use, the stock solution composition can be diluted 10 to 1000 times with the above-mentioned water or organic solvent, or a mixture of water and an organic solvent.

[0035] Next, the cleaning method of the silicon carbide substrate of the present invention will be described. The cleaning method of the present invention comprises the step of contacting the cleaning composition of the present invention with a silicon carbide substrate. The contacting step is not limited thereto, and examples thereof include a cleaning step after polishing such as etching or CMP. The contacting method is not limited thereto, and examples thereof include single-wafer cleaning methods combined with brushing, batch spray cleaning methods, and batch cleaning methods.

[0036] The contact atmosphere is not limited thereto, and examples thereof include air, nitrogen, and vacuum. Air and nitrogen are preferred. The contact time can be appropriately selected depending on the intended purpose, but is not limited thereto. For single-wafer cleaning methods using a combination of brush cleaning and spray or nozzle-spray cleaning, the cleaning time is 0.5 to 5 minutes. For single-wafer cleaning methods using a combination of surface mount spray cleaning and surface mount immersion cleaning, the cleaning time is 0.5 to 30 minutes. The temperature is not limited thereto. For a single wafer cleaning method using a combination of brush cleaning and a single wafer cleaning method using a spray or nozzle spray cleaning solution, the cleaning temperature is 20 to 50°C. For a wafer spray cleaning method or a wafer immersion cleaning method, the cleaning temperature is 20 to 100°C. The above conditions can be appropriately combined depending on the application.

[0037] Although the present invention has been described in detail above based on preferred embodiments, the present invention is not limited thereto, and each component may be replaced with any component capable of performing a similar function, or any component may be added. Example

[0038] The present invention will be described in more detail below with reference to the following examples, but the present invention is not limited to these examples.

[0039] (Examples 1 to 6 and Comparative Examples 1 to 4) <Cleansing Properties of Cleaning Compositions (Mn Surface Concentration)> (1) Preparation of cleaning composition The components shown in Table 1 were mixed with water to achieve the concentrations shown in Table 1 to obtain the cleaning compositions of Examples 1 to 6 and Comparative Examples 1 to 4.

[0040] (2) Preparation of evaluation substrate After cleaning the silicon carbide substrate with a mixture of hydrogen peroxide (30 wt%) and sulfuric acid (96 wt%) (volume ratio 1:6), potassium permanganate was dissolved in water by spin coating to make the surface concentration of manganese (Mn) reach 10 13 atoms / cm 2 After the contaminated substrate was immersed in each cleaning solution at room temperature for 3 minutes (without stirring), the substrate was removed and rinsed with flowing ultrapure water for 3 minutes. After drying, the substrate for measurement was obtained.

[0041] (3) Mn cleaning performance evaluation The Mn concentration on the surface of the substrate for measurement was measured using TXRF (total reflection X-ray fluorescence spectrometer, manufactured by Rigaku Corporation, model: 3800e) to evaluate the cleaning properties of the cleaning composition. 2 The results corresponding to each cleaning composition are shown in Table 1. The results obtained show that the cleaning composition of the present invention is able to remove manganese well under acidic conditions.

[0042] Table 1

Claims

1. A cleaning liquid composition for cleaning a silicon carbide substrate polished with a manganese compound-containing abrasive or a silicon carbide substrate etched with a manganese compound-containing etching solution, characterized in that: The invention comprises a reducing agent, a pH adjusting agent and water, and has a pH value of less than 5. The reducing agent is one or more selected from the following group: a six-membered ring compound in which two or more hydroxyl groups are directly bonded to the ring, glyoxylic acid and diethylhydroxylamine.

2. The composition according to claim 1, characterized in that It comprises a six-membered ring compound represented by the following formula (1) in which two or more hydroxyl groups are directly bonded to the ring, In the formula, R1-R6 are each independently H, OH, COOH, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, wherein at least two of R1-R6 are OH.

3. The cleaning liquid composition according to claim 1 or 2, characterized in that It comprises one or more six-membered ring compounds in which two or more hydroxyl groups are directly bonded to the ring selected from the group consisting of gallic acid, catechol, resorcinol, hydroquinone, pyrogallol and methylcatechol.

4. The cleaning liquid composition according to any one of claims 1 to 3, characterized in that The pH adjuster is an inorganic acid or an organic acid.

5. The cleaning liquid composition according to any one of claims 1 to 4, characterized in that The pH adjuster is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, oxalic acid, malonic acid, succinic acid, malic acid, tartaric acid, and citric acid.

6. The cleaning liquid composition according to any one of claims 1 to 5, characterized in that One or more polysulfonic acid compounds are also included as surfactants.

7. The cleaning liquid composition according to any one of claims 1 to 6, characterized in that The concentration of the reducing agent is 0.001 mass percent or more and 1 mass percent or less.

8. A stock solution composition for a cleaning liquid composition according to any one of claims 1 to 7, characterized in that: The cleaning liquid composition is obtained by diluting the mixture 10 to 1000 times.

9. A method for cleaning a silicon carbide substrate, characterized in that: The following steps are involved: The cleaning liquid composition according to any one of claims 1 to 7 is brought into contact with a silicon carbide substrate polished with a manganese compound-containing abrasive or a silicon carbide substrate etched with a manganese compound-containing composition.

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