Cleaning composition of silicon carbide substrate

Abstract

To provide a cleaning composition of a manganese contamination of a silicon carbide substrate, capable of transporting a product in a solution while having a high safety.SOLUTION: A cleaning composition for cleaning a silicon carbide substrate polished by a polishing agent containing a manganese compound or a silicon carbide substrate etched by an etching liquid containing the manganese compound, contains a reductant agent, a pH adjustment agent, and water. The pH is less than 5, and the reductant agent is one or two kinds of the agents, selected from a group consisting of a six-membered ring compound, a glyoxylic acid, and a diethylhydroxylamine, to which two or more hydroxyl groups are directly coupled.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Compared to silicon, the currently mainstream semiconductor material, silicon carbide (SiC) has excellent physical properties such as a wide band gap, high dielectric breakdown field strength, and high thermal conductivity. Therefore, it is expected to be a semiconductor material for power devices that enable high-power control and energy savings.

[0003] The device manufacturing process generally includes a polishing step for planarizing the substrate and an etching step for dissolving and removing layers damaged by processing, but silicon carbide has a high hardness, so it cannot be polished or etched by polishing with silica slurry or etching with strong acids such as hydrofluoric nitric acid, which have been used in the past to process silicon substrates, and it has a problem that processing takes a long time. To address this problem, methods have been proposed in which permanganate ions are added as an oxidizing agent to the slurry or etching solution, and manganese oxide is used as an abrasive grain in the slurry, but high concentrations of manganese contamination remain on the silicon carbide after polishing or etching.

[0004] Manganese oxides used in abrasives include MnO2 and Mn3O4, but manganese compounds with valences III and IV are insoluble, and it is believed that permanganate compounds added to slurries and etching solutions produce insoluble manganese compounds. Once such insoluble manganese compounds adhere to the substrate, they are very difficult to clean.

[0005] RCA cleaning is widely used for cleaning silicon carbide, and its basic form is a combination of SC-1 cleaning (Standard Clean 1) made of ammonia water and hydrogen peroxide water to remove particles, SC-2 cleaning (Standard Clean 2) made of hydrochloric acid and hydrogen peroxide water to remove metal impurities, and cleaning with hydrofluoric acid. As a cleaning method other than RCA cleaning, Patent Document 1 proposes a cleaning agent containing at least one of ascorbic acid and erythorbic acid and having a pH of 6 or less. Patent Document 2 proposes a cleaning method for semiconductor substrates that uses a reducing agent such as ascorbic acid and an acid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO 2013 / 088928 [Patent Document 2] Japanese Patent Application Publication No. 11-251280 Summary of the Invention [Problem to be solved by the invention]

[0007] The RCA cleaning, which is widely used for cleaning silicon carbide, has problems in that it uses high-concentration strong acid and strong alkaline cleaning solutions at high temperatures and highly toxic hydrofluoric acid at high concentrations, which places a large burden on safety and the environment. Patent documents 1 and 2 propose cleaning agents containing ascorbic acid or erythorbic acid as reducing agents, but ascorbic acid and erythorbic acid, which have strong reducing power, are easily oxidized and decomposed in solution, and their content rapidly decreases, so that the cleaning agent product cannot be transported in the form of a solution. For this reason, the cleaning solution must be prepared from ascorbic acid or erythorbic acid transported as a solid at the user's site, which requires the introduction of cleaning solution preparation equipment and filtration equipment, resulting in problems such as increased work hours and costs.

[0008] An object of the present invention is to provide a cleaning solution composition for cleaning manganese contamination on a silicon carbide substrate, which is excellent in safety and stability and can be delivered as a product in the form of a solution. [Means for solving the problem]

[0009] In the course of intensive research aimed at solving the above problems, the present inventors discovered that a specific reducing agent selected from the group consisting of a six-membered ring compound having two or more hydroxyl groups directly bonded to a ring, glyoxylic acid, and diethylhydroxylamine can effectively remove manganese compounds on a silicon carbide substrate under acidic conditions, and as a result of further research, they have completed the present invention.

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

[0011] [3] The cleaning liquid composition according to [1] or [2] above, which contains one or more six-membered ring compounds having two or more hydroxyl groups 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 the above [1] to [3], wherein the pH adjuster is an inorganic acid or an organic acid. [5] The cleaning liquid composition according to any one of [1] to [4] above, wherein 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 the above [1] to [5], further comprising one or more polysulfonic acid compounds as a surfactant. [7] The cleaning liquid composition according to any one of the above [1] to [6], wherein the concentration of the reducing agent is from 0.001% by mass to 1% by mass. [8] A concentrate composition for a cleaning liquid composition according to any one of [1] to [7] above, which is used to obtain the cleaning liquid composition by diluting it 10 to 1,000 times. [9] A method for cleaning a silicon carbide substrate, comprising a step of contacting the cleaning liquid composition according to any one of the above [1] to [7] with a silicon carbide substrate that has been polished with an abrasive containing a manganese compound, or with a silicon carbide substrate that has been etched with a composition containing a manganese compound. Effect of the Invention

[0013] According to the cleaning liquid composition of the present invention, manganese compounds on a silicon carbide substrate can be safely and simply removed by using a reducing agent selected from the group consisting of six-membered ring compounds having two or more hydroxyl groups directly bonded to a ring, glyoxylic acid, and diethylhydroxylamine under acidic conditions. Although the mechanism is not necessarily clear, it is considered that the reducing agent used in the present invention acts stably on insoluble manganese compounds under acidic conditions, reducing insoluble manganese compounds with a valence of three or four to highly soluble manganese compounds with a valence of two, which then dissolve in the cleaning composition, thereby removing the manganese compounds.

[0014] The cleaning solution composition of the present invention does not contain highly toxic components and does not require a cleaning process using multiple cleaning solutions as in RCA cleaning. In addition, since the cleaning solution composition of the present invention does not require consideration of oxidative decomposition of the reducing agent, it can be transported in the form of a solution and does not require preparation of a cleaning solution when used. Therefore, the cleaning solution composition of the present invention can save each user the trouble of installing and preparing preparation equipment, and greatly contributes to reducing the manufacturing costs of silicon carbide devices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] BEST MODE FOR CARRYING OUT THE DISCLOSURE Preferred embodiments of the cleaning composition for silicon carbide substrates and the method for cleaning silicon carbide substrates according to the present invention will now be described in detail. The cleaning liquid composition of the present invention is used for cleaning a silicon carbide substrate which has been polished with an abrasive containing a manganese compound, or a silicon carbide substrate which has been etched with an etching liquid containing a manganese compound.

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

[0017] The manganese compounds contained in the polishing agent and etching solution are manganese compounds usually used in polishing agents and etching solutions, such as manganese dioxide, dimanganese trioxide, and permanganates. The manganese compounds remaining in the silicon carbide substrate may include, in addition to the manganese compounds described above, those in the form of ions such as manganese ions and permanganese ions.

[0018] The reducing agent contained in the cleaning liquid composition of the present invention may be any agent capable of changing the valence of the insoluble manganese compound, and from the viewpoint of being able to stably and effectively reduce the insoluble manganese compound under acidic conditions, a six-membered ring compound having two or more hydroxyl groups directly bonded to the ring, glyoxylic acid, and diethylhydroxylamine are preferred. The reducing agents may be used alone or in combination of two or more.

[0019] The six-membered ring compound having two or more hydroxyl groups directly bonded to the ring is not particularly limited as long as it can effectively reduce the insoluble manganese compound, and an example of such a compound is a compound represented by the following formula (1). [ka] During the ceremony, R1 to R6 are each independently H, OH, COOH, alkyl having 1 to 4 carbon atoms, alkenyl having 2 to 4 carbon atoms, or alkoxy having 1 to 4 carbon atoms, where at least two, preferably two or three of R1 to R6 are OH.

[0020] Six-membered ring compounds having two or more hydroxyl groups directly bonded to the ring can stably act as reducing agents on insoluble manganese compounds under acidic conditions and reduce them. Specific 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% by mass or more, more preferably 0.001% by mass or more. This allows the manganese compound to be sufficiently and efficiently reduced from a valence III or valence IV to a valence II. The upper limit of the concentration of the reducing agent is not particularly limited, but is, for example, 10% by mass or less, more preferably 1% by mass or less. In one embodiment of the present invention, the concentration of the reducing agent is 0.0001% by mass or more and 10% by mass or less, and in a preferred embodiment, the concentration of the reducing agent is 0.001% by mass or more and 1% by mass 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, but the pH adjuster has the effect of releasing the manganese compound remaining on the silicon carbide substrate from the substrate surface and dissolving it in the cleaning composition in combination with the reducing agent. Examples of such pH adjusters include inorganic acids and organic acids, and one of these can be used alone or two or more can be used in combination.

[0023] Examples of 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 contains one or more inorganic acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

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

[0025] In a preferred embodiment, the cleaning solution 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, and is preferably less than 5, more preferably 4 or less, and further preferably 3 or less. This allows the manganese compound on the surface of the silicon carbide substrate to be appropriately dissolved in the cleaning liquid composition and removed. If the pH is 5 or more, the solubility decreases and the removability deteriorates.

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

[0028] The cleaning liquid composition of the present invention may also contain a surfactant to improve the removability of fine particles. The type of surfactant is appropriately selected, and is not limited thereto, but a polysulfonic acid compound is preferred. Examples of the polysulfonic acid compound include naphthalenesulfonic acid formaldehyde condensates, polystyrenesulfonic acid, ligninsulfonic acid, and salts thereof. In a preferred embodiment, the cleaning liquid composition of the present invention contains 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%, preferably 0.001 to 1.0 mass%, and particularly preferably 0.001 to 0.1 mass%. If the concentration exceeds the above range, the effect of improving the removability of fine particles decreases, so that it is economical to use the surfactant within the above range.

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

[0031] Examples of such organic solvents include various organic solvents miscible with water, such as alcohol solvents, ether solvents, and ketone solvents. Among these, 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 polyhydric alcohols such as glycerin.

[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 %, preferably 50 to 99.99 mass %, and particularly preferably 80 to 99.99 mass %. The concentration of the organic solvent in the present invention is not particularly limited, but is, for example, 0.0001 to 20% by mass, preferably 0.001 to 10% by mass, and particularly preferably 0.01 to 1% by mass.

[0034] It is preferable to use each component of the cleaning liquid composition of the present invention at the above-mentioned concentrations. However, high-concentration products in which each component is 10 to 1,000 times more concentrated are also stable, so that high-concentration products can be prepared for storage, transportation, etc., and the high-concentration products can also be diluted before use. Therefore, the present invention also relates to a concentrate composition for the cleaning liquid composition of the present invention, which is used to obtain the cleaning liquid composition of the present invention by diluting it 10 to 1,000 times. When the concentrate composition is used after dilution, it can be diluted 10 to 1000 times with the above-mentioned water or organic solvent, or a mixture of water and an organic solvent, before use.

[0035] Next, the method for cleaning a silicon carbide substrate of the present invention will be described. The cleaning method of the present invention includes a step of contacting the above-mentioned cleaning composition of the present invention with a silicon carbide substrate. The contact step includes, but is not limited to, a cleaning step after polishing such as etching or CMP. The contact method includes, but is not limited to, a single-wafer cleaning method using brush scrubbing in combination, a batch-type spray cleaning method, and a batch-type cleaning method.

[0036] The atmosphere for contacting includes, but is not limited to, air, nitrogen atmosphere, vacuum, etc. Among these, air and nitrogen atmosphere are preferable. The contact time is appropriately selected depending on the purpose, and is not limited to, but is 0.5 to 5 minutes in the case of single-wafer cleaning method using brush scrub in combination and single-wafer cleaning method in which cleaning liquid is sprayed from a spray or nozzle, and is 0.5 to 30 minutes in the case of patch type spray cleaning method and patch type immersion cleaning method. The temperature is not limited thereto, but in the case of a single-wafer cleaning method in which a brush scrub is used in combination and a single-wafer cleaning method in which a cleaning solution is sprayed from a spray or a nozzle, it is 20 to 50° C., and in the case of a patch-type spray cleaning method and a patch-type immersion cleaning method, it is 20 to 100° C. The above-mentioned conditions can be appropriately combined depending on the purpose.

[0037] The present invention has been described in detail above based on a preferred embodiment, but the present invention is not limited to this, and each component can be replaced with any component that can perform a similar function, or any component can be added. EXAMPLES

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

[0039] (Examples 1 to 6 and Comparative Examples 1 to 4) <Cleaning properties of cleaning composition (Mn surface concentration)> (1) Preparation of cleaning composition The components shown in Table 1 were mixed with water to give the concentrations shown in Table 1, to obtain cleaning compositions of Examples 1-6 and Comparative Examples 1-4.

[0040] (2) Preparation of the evaluation board After cleaning the silicon carbide substrate with a mixture of hydrogen peroxide (30% by weight) and sulfuric acid (96% by weight) (volume ratio 1:6), the surface concentration of manganese (Mn) was adjusted to 10 13 atoms / cm 2 The contaminated substrates were immersed in each cleaning solution at room temperature for 3 minutes without stirring, then removed and rinsed with running ultrapure water for 3 minutes and dried to obtain substrates for measurement.

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

[0042] [Table 1]

Claims

1. A cleaning liquid composition for cleaning a silicon carbide substrate that has been polished with an abrasive containing a manganese compound, or a silicon carbide substrate that has been etched with an etching solution containing a manganese compound, the cleaning liquid composition comprising a reducing agent, a pH adjuster, and water, and having a pH of less than 5, wherein the reducing agent is one or more selected from the group consisting of a six-membered ring compound having two or more hydroxyl groups directly bonded to the ring, glyoxylic acid, and diethylhydroxylamine.

2. The following formula (1) 【Chemistry 1】 During the ceremony, R １ ~R ６ are each independently H, OH, COOH, alkyl having 1 to 4 carbon atoms, alkenyl having 2 to 4 carbon atoms, or alkoxy having 1 to 4 carbon atoms, where R １ ~R ６ at least two of which are OH; The composition of claim 1 , comprising a six-membered ring compound represented by the formula:

3. 2. The cleaning liquid composition according to claim 1, comprising 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 claim 1 , wherein the pH adjuster is an inorganic acid or an organic acid.

5. 2. The cleaning solution composition of claim 1, wherein 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 claim 1, further comprising one or more polysulfonic acid compounds as surfactants.

7. The cleaning liquid composition according to claim 1 , wherein the concentration of the reducing agent is 0.001% by mass or more and 1% by mass or less.

8. 8. The concentrate composition for the cleaning liquid composition according to claim 1, which is used to obtain the cleaning liquid composition by diluting it 10 to 1000 times.

9. A method for cleaning a silicon carbide substrate, comprising a step of bringing the cleaning liquid composition according to any one of claims 1 to 7 into contact with a silicon carbide substrate that has been polished with an abrasive containing a manganese compound, or a silicon carbide substrate that has been etched with a composition containing a manganese compound.

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