Clearing polishing liquid and polishing method using the clearing polishing liquid

Abstract

The object of the present invention is to provide a polishing liquid that can detect the surface to be polished and determine the polishing end point while reliably maintaining fine and flat polishing in accordance with the trend toward higher integration and multi-layering of circuits. [Solution] The present invention solves the problem by providing a transparent polishing liquid that contains silica particles and an additive including a polyol compound selected from glycerin or polyglycerin, with an average degree of polymerization of 1 to 20 calculated from the hydroxyl value, and that brings the refractive index of the solvent containing the additive closer to that of the silica particles, and that has the function of adjusting the mechanical polishing force of the silica particles and is used to optically detect the polishing endpoint.

Description

[Technical Field]

[0001] The present invention relates to a polishing liquid used in the manufacture of semiconductor devices, and to a polishing method using the polishing liquid, which is used in the polishing process and in detecting and determining the end point of the process. [Background technology]

[0002] In today's world, with advanced technological innovations occurring in various fields such as autonomous driving, robots, AI, and information and communications technology, efforts are being made to further enhance the functionality and performance of semiconductor elements, which are key devices, and efforts are being made to further miniaturize and multilayer integrated circuits along with the integration of circuits. In this context, polishing technology is becoming increasingly important in the manufacturing process, as it removes excess or unnecessary parts by polishing to form precise circuit patterns on the wafer surface, while also flattening the surface to laminate multiple circuit patterns in layers.

[0003] The main method used to polish wafer surfaces is chemical mechanical polishing (CMP). This polishing process involves chemicals and abrasive particles that chemically dissolve the material being polished while mechanically scraping it off to flatten the surface. In order to obtain an optimal wafer surface, the CMP polishing process detects and determines when the process is complete based on the polishing status of the surface.

[0004] For example, Patent Document 1 discloses a technology that focuses on a motor that rotates or drives a polishing table on which a polishing pad is placed, a holder that holds an object to be polished, or an arm that swings the holder. Specifically, a digital signal corresponding to the load on the motor is monitored, and the completion point of polishing (hereinafter also referred to as the "polishing end point") is detected and determined based on fluctuations in the signal depending on the polishing state.

[0005] Patent Document 2 discloses a technology for measuring the film thickness of the film to be polished on the wafer surface using an optical film thickness measurement device to detect and determine the polishing endpoint. This device irradiates the wafer surface with light during the polishing process and measures the film thickness by analyzing the spectrum of the reflected light to detect and determine the polishing state. In the technology of Patent Document 2, in order to suppress a decrease in the intensity of the reflected light due to the polishing liquid supplied to the wafer surface during the polishing process, a cleaning liquid is supplied to the position to be polished and the polishing liquid is successively removed while the film thickness is measured and the polishing endpoint is detected. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-124546 [Patent Document 2] Japanese Patent Publication No. 2023-148227 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with the increasing integration, multi-layering, and miniaturization of semiconductor elements, there have been increasing demands for finer circuit wiring patterns formed on wafer surfaces and for in-plane uniformity without irregularities or undulations. As seen in Patent Documents 1 and 2, various devices and methods have been proposed for determining the polishing endpoint to avoid overpolishing.

[0008] In particular, in Patent Document 2, the polishing liquid is interposed between the surface of the wafer and the object to be polished, and because it contains ingredients such as abrasive grains, it is prone to becoming cloudy due to light reflection, making it difficult to see the surface of the object to be polished, which is thought to have an effect on determining the polishing endpoint, and it appears that there is still room for consideration in addressing this effect. Meanwhile, in such a situation, the polishing liquid is significantly involved in the performance of the semiconductor elements to be manufactured, and in order to meet the above-mentioned high level of demands, it is important to maintain and improve the polishing function of the polishing liquid.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a polishing liquid that is capable of detecting the surface to be polished and determining the polishing end point while reliably maintaining fine and flat polishing. [Means for solving the problem]

[0010] The polishing liquid of the present invention contains silica particles and an additive containing a polyol compound selected from glycerin or polyglycerin, having an average degree of polymerization of 1 to 20 calculated from the hydroxyl value, and is a transparent polishing liquid in which the refractive index of the solvent containing the additive is made close to that of the silica particles, and is characterized by having the function of adjusting the mechanical polishing force of the silica particles and being used to optically detect the polishing endpoint, thereby solving the above-mentioned problems.

[0011] The clarifying polishing liquid of the present invention is characterized in that the light transmittance is 60% or more and 100% or less.

[0012] The clarifying polishing liquid of the present invention is characterized in that the wavelength of light transmitted therethrough is 300 nm to 800 nm.

[0013] The polishing solution for transparency of the present invention contains an oxidizing agent, a complexing agent, and a film-forming agent, and is characterized by being suitable for use in a process for forming a metal film on a wafer surface.

[0014] In another aspect of the present invention, there is provided a polishing method using a transparent polishing liquid, i.e., a transparent polishing liquid, which contains silica particles and an additive containing a polyol compound selected from glycerin or polyglycerin having an average degree of polymerization of 1 to 20, and which brings the refractive index of the solvent containing the additive close to that of the silica particles, and which monitors the polished surface of the wafer surface via the transparent polishing liquid while polishing the wafer surface, thereby making it possible to detect and determine the polishing endpoint.

[0015] The above-described polishing method according to the present invention is characterized in that, in the step of forming a metal film on the wafer surface, the surface to be polished is monitored to detect and determine the polishing end point while removing the excess metal film formed on the wafer surface.

[0016] In yet another aspect of the present invention, there is provided a polishing liquid kit for a transparent polishing liquid, which includes a first solution containing silica particles, a complexing agent, and a film-forming agent, and a second solution containing an additive containing a polyol compound selected from glycerin and polyglycerin having an average degree of polymerization of 1 to 20, and which includes the first solution and the second solution, and which can be used in a process of forming a metal film layer on a wafer surface. [Effects of the Invention]

[0017] The transparent polishing solution of the present invention allows the polishing state of the surface to be polished to be monitored by light irradiation in parallel with the CMP polishing process without becoming cloudy. This allows for highly accurate detection and determination of the polishing end point based on the image obtained by monitoring the actual polishing state. Furthermore, by utilizing the irradiated light, film thickness measurement is also performed, taking the wafer film thickness into consideration. Furthermore, highly accurate detection and determination of the polishing end point is also possible.

[0018] The clarifying polishing liquid of the present invention has the ability to transmit light in the wavelength range from part of the ultraviolet range to the visible light range, making it possible to monitor the polished surface with light of a wide range of wavelengths.

[0019] This transparent polishing solution contains an additive containing a polyol compound selected from glycerin or polyglycerin, which adjusts the mechanical polishing power of the silica particles as abrasive grains, allowing the polishing process to be performed while monitoring the polishing process state of the surface to be polished and preventing over-polishing, scratches, and other surface defects.In particular, by adding an oxidizing agent, a complexing agent, and a film-forming agent, the solution can be suitably used in the process of forming a metal film on the wafer surface.

[0020] Furthermore, by using a kit for a transparency polishing solution in which an additive containing a polyol compound selected from glycerin or polyglycerin is used as the second solution, it is possible to perform a polishing process that takes into consideration processability and workability at the beginning of polishing, add an additive near the end of the polishing process, and perform a high-precision process while monitoring the polished surface. This kit for a transparency polishing solution makes it possible to adjust the polishing performance according to the polishing state of the wafer surface, while monitoring the polishing state, and perform a polishing process with high precision and high flatness. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described. Note that this embodiment is merely an example for understanding the present invention, and the present invention is not limited to this embodiment.

[0022] The polishing liquid of the present invention contains silica particles as abrasive grains and an additive containing glycerin or polyglycerin (hereinafter referred to as a "polyol compound") having an average degree of polymerization of 1 to 20, calculated from the hydroxyl value, and is a transparent solution in which the refractive indexes of the abrasive grains and the additive are close to each other (hereinafter also referred to as a "clarifying polishing liquid"). The transparent polishing liquid of the present invention also contains an oxidizing agent, a complexing agent, and a film-forming agent in addition to the silica particles and the polyol compound.

[0023] This polishing liquid is based on chemical mechanical polishing (hereinafter also referred to as "CMP") and contains a component that has a mechanical polishing action using abrasive grains and a component that has a chemical polishing action that causes dissolution or alteration of the polishing surface using chemicals, etc. These components do not only act individually during polishing, but are selected and blended so that their actions mutually enhance each other. Each component of the clarifying polishing liquid of the present invention is described below.

[0024] <About silica particles> The silica particles contained in the transparency polishing solution of the present invention adhere to the surface of the object to be polished and act as abrasive grains with a mechanical polishing function, scraping it off by physical action. In addition, since the silica particles contribute to the mechanical action in CMP polishing, the type and content of the particles to be used can be determined taking into consideration the chemical action of other components.

[0025] Regarding silica particles, examples of silica include amorphous silica, crystalline silica, fused silica, spherical silica, synthetic silica, hollow silica, fumed silica, and colloidal silica. Among these, abrasive grains containing colloidal silica and fumed silica are particularly preferred, and abrasive grains containing colloidal silica are more preferred. Furthermore, silica particles with modified surfaces may be used.

[0026] There are no particular restrictions on the particle size of the silica particles, and silica particles with an average particle size of 5 nm to 200 nm are used. Regarding the refractive index of the silica particles, the refractive index of the polishing liquid containing silica particles is in the range of 1.400 to 1.460.

[0027] To ensure the transparency of the polishing liquid, the content of silica particles can be set to a range of 0.1% by mass to 7.0% by mass relative to the total amount of the clarifying polishing liquid. If the content of silica particles is less than 0.1% by mass, the polishing performance will decrease, and if it is more than 7.0% by mass, the polishing liquid will become cloudy and it will be difficult to maintain transparency. Furthermore, the content of silica particles or the additives described below in the clarifying polishing liquid is preferably adjusted so that the refractive index of the solvent component containing the additives of the polishing liquid is 0.8 to 1.2 times the refractive index of the silica particles.

[0028] Within the above range of silica particle content, the transparent polishing liquid has polishing performance that balances processability such as polishing speed and flatness of the wafer surface. Furthermore, in order to maintain transparency while increasing the polishing speed and ensuring high flatness, the silica particle content is more preferably 1.0 mass% or more. Regarding the upper limit, in order to ensure higher transparency of the polishing liquid, the silica particle content is more preferably 6.0 mass% or less.

[0029] <About oxidizing agents> The oxidizing agent contained in the polishing solution for transparency of the present invention oxidizes the surface to be polished and mainly acts to improve the polishing rate. For example, when polishing a metal film deposited on the wafer surface, the oxidizing agent functions as a metal dissolving agent, oxidizing the metal film to make the metal easier to remove by polishing.

[0030] The inclusion of this oxidizing agent weakens the metal film, maintaining high polishing performance with the CMP abrasive grains and polishing pad. In particular, when used in combination with a complexing agent, the chemical polishing action of etching and the mechanical polishing action of the abrasive grains on the oxidized metal film can be obtained, ensuring higher polishing performance and improving the polishing rate while suppressing over-polishing and corrosion.

[0031] The oxidizing agent contained in the transparency polishing liquid of the present invention includes oxidizing metal salts and oxidizing non-metallic compounds. Examples of oxidizing metal salts include sulfates, nitrates, iron salts, aluminum salts, potassium salts, and permanganates. Examples of oxidizing non-metallic compounds include hydrogen peroxide, potassium periodate, ammonium persulfate, hypochlorous acid, and ozone water. Hydrogen peroxide is preferred as the oxidizing agent in terms of stability after addition. The oxidizing agents can be used alone or in combination of two or more.

[0032] The oxidizing agent content of the clarifying polishing liquid can be in the range of 0.1 to 2.5% by mass relative to the total amount of the polishing liquid, taking into consideration the need to ensure the transparency of the polishing liquid. If the oxidizing agent content is greater than 2.5% by mass, the polishing liquid becomes cloudy, making it difficult to maintain transparency. Furthermore, within this range, the clarifying polishing liquid exhibits polishing performance that balances processability, such as polishing speed, with the flatness of the surface to be polished. Furthermore, to ensure high processability and flatness while maintaining transparency, the content is preferably in the range of 0.1 to 2.0% by mass.

[0033] <About additives> The additive contained in the clarifying polishing solution of the present invention is a solution containing a polyol compound, and by blending and adding it to a polishing solution containing abrasive grains, the polishing solution can be made transparent from a cloudy state.In addition, since this additive contains a polyol compound, it contributes to the wettability of the polished surface, has the function of suppressing corrosion that may occur during polishing, and promotes high flatness while maintaining a higher polishing rate.This will be explained in detail below.

[0034] The additive contained in the transparency polishing liquid contains a polyol compound selected from glycerin and polyglycerin, which has an average degree of polymerization calculated from the hydroxyl value of 1 to 20. The average degree of polymerization of this glycerin or polyglycerin is calculated from the hydroxyl value obtained by terminal analysis using the following formulas (1) and (2), where n represents the average degree of polymerization calculated from the hydroxyl value. Molecular weight=74n+18 (1) Hydroxyl value = 56110(n+2) / molecular weight (2)

[0035] The hydroxyl value in formula (2) is a numerical value that indicates the number of hydroxyl groups contained in glycerin or polyglycerin, and refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid required to acetylate the free hydroxyl groups contained in 1 g of glycerin or polyglycerin. The number of milligrams of potassium hydroxide is calculated in accordance with "Standard Test Methods for the Analysis of Fats, Oils and Related Materials, 2013 Edition, Established by the Japan Oil Chemists' Society," edited by the Japan Oil Chemists' Society.

[0036] Generally, polishing solutions containing abrasive grains become cloudy because the difference in refractive index between the abrasive grains and the solvent components such as water makes it difficult for light to pass through the solution. This state is a phenomenon related to the general refraction of light in a substance containing different media.

[0037] Therefore, focusing on the fact that polyol compounds have a relatively high refractive index, the inventors have conducted extensive research and found that when the additive of the present invention is added to a general polishing liquid and the refractive index of the solvent component containing the additive in the polishing liquid is brought closer to the refractive index of the abrasive grains, the polishing liquid becomes transparent.The transparent polishing liquid of the present invention is a liquid that is made transparent by blending an additive containing a polyol compound based on the results of this research, and bringing the refractive index of the solvent component in the polishing liquid closer to the refractive index of the silica particles.

[0038] The refractive index of this additive is 1.410 to 1.450 at 25°C in a solution mixed with pure water as a solvent. The content of this additive is adjusted and blended based on the refractive index of the silica particles contained in the polishing liquid so that the polishing liquid becomes transparent. Specifically, transparency can be achieved when the content of this additive is in the range of 55% by mass to 75% by mass of the total amount of the transparent polishing liquid. If the content of this additive is less than 55% by mass or more than 75% by mass, the polishing liquid becomes cloudy, making it difficult to ensure transparency.

[0039] The above-mentioned "clarification of the polishing liquid" in the present invention refers to a state of the polishing liquid in which the refractive index of the solvent containing the additive is brought closer to that of the silica particles in the polishing liquid, making it possible to detect and determine the end point of polishing with this polishing liquid. In addition, when expressed in terms of light transmittance, this state is 60% or more and 100% or less. Light transmittance is indicated by the light transmittance calculated from absorbance. Specifically, light from the ultraviolet to visible light range is irradiated onto the target material, and the absorbance is measured with an absorptiometer based on the amount of light that transmits, and the light transmittance is calculated from the measurement results. Note that measurement is also possible using a measurement method such as irradiating the target material with light using a spectroscope and measuring the light transmittance based on the amount of light that transmits.

[0040] The polyol compound contained in the additive preferably has a metal content of 100 ppb or less, which makes it possible to further ensure the transparency of the polishing liquid by using a polyol compound with a very low impurity content and very high transparency.

[0041] Next, we will explain the contribution of this additive to polishing performance. This additive has the function of adjusting the mechanical polishing force of silica particles depending on its content in the polishing liquid. Because this additive contains a polyol compound, it also exhibits excellent performance in terms of wettability with silica particles and dispersibility of silica particles in the polishing liquid. Therefore, it is thought that this function is due to the silica particles being uniformly mixed and dispersed in the polishing liquid during the polishing process, and being covered by the additive, which improves contact with the polished surface, while changing the frictional force depending on the wettability and viscosity of the additive.

[0042] Furthermore, since this additive contains a polyol compound, it has the effect of reducing the magnitude of the corrosion current that occurs between metals during polishing, as will be described later, thereby allowing the silica particles to exert a stable polishing power while suppressing overpolishing such as edging.

[0043] To obtain a clarifying polishing liquid having such a function, the content of the present additive can be set to a range of 55% by mass or more and 75% by mass or less relative to the total amount of the present polishing liquid. Note that, in the case of silica particles in the clarifying polishing liquid of the present invention, if the content of the present additive is less than 55% by mass or more than 75% by mass, as described above, the polishing liquid becomes cloudy and it is difficult to ensure transparency.

[0044] This additive enhances the wettability of the wafer surface while maintaining the transparency of the polishing liquid, and its dispersibility allows the polishing power of the silica particles to be effectively applied to the wafer surface, while its corrosion-inhibiting effect prevents surface defects such as scratches and over-polishing on the wafer surface, thereby achieving uniform flatness. The polishing performance of the additive-imparted clear polishing liquid will be explained in detail later.

[0045] <About complexing agents> The complexing agent contained in the polishing solution for polishing transparency of the present invention coordinates with metal ions to form a complex, which dissolves the metal ions in water or captures and inactivates the metal. Furthermore, when used with an oxidizing agent, it improves the polishing rate. This allows the metal particles generated during polishing of a metal film on the wafer surface to dissolve in the complexing agent, thereby maintaining a high polishing rate while suppressing clogging of the polishing pad.

[0046] Furthermore, this complexing agent dissolves the fine particles of the removed metal, thereby suppressing their deposition in the polishing solution, and effectively prevents surface defects such as scratches on the wafer surface, erosion, and dishing of metal wiring, as well as over-polishing, which are caused by these fine particles of the removed metal during polishing.

[0047] Examples of complexing agents contained in the transparentization polishing liquid of the present invention include organic acids, organic acid salts, and organic acid esters. Examples of organic acids include carboxylic acids (acetic acid, propionic acid, benzoic acid, lactic acid, malonic acid, succinic acid, citric acid, malic acid, diglycolic acid, isophthalic acid, methylsuccinic acid, oxalic acid, tartaric acid, picolinic acid, phthalic acid, adipic acid, and glutaric acid), sulfonic acids, and amino acids. Examples of amino acids include glycine, alanine, leucine, and aspartic acid. Examples of organic acid salts include ammonium salts. Examples of organic acid esters include aminoacetic acid. Among these, amino acids are particularly preferred, with glycine being more preferred. The complexing agents may be contained alone or in combination of two or more.

[0048] The content of the complexing agent does not particularly contribute to the transparency of the transparent polishing liquid, but can be set to 0.01 mass % or more and 20 mass % or less relative to the total amount of the transparent polishing liquid, from the viewpoint of maintaining and improving processing efficiency in terms of polishing speed, etc., and preventing over-polishing and erosion.

[0049] <About film-forming agents> The film-forming agent contained in the clarifying polishing solution of the present invention forms a complex with the metal, thereby preventing excessive corrosion of the polished surface. When removing excess metal film on the wafer surface by polishing, the chemical polishing action of the polishing solution may corrode the metal film in the required areas by etching, oxidation, etc. When contained in the polishing solution, this film-forming agent forms a complex with the metal during the polishing process, forming a protective film on the surface of the metal film that suppresses corrosion.

[0050] Regarding this protective film, for example, a metal film formed on the surface of an interlayer insulating layer of a wafer in a circuit wiring formation process is polished together with the protective film formed thereon by the mechanical polishing action of this polishing liquid while being planarized. At that time, the portion where the excess metal film exists is uneven and thicker than other portions, and comes into contact with the abrasive grains and polishing pad first, so that the protective film of the metal film deposited in recesses such as trench patterns is polished away while remaining, thereby preventing corrosion of the metal film in the recesses.

[0051] In other words, the film-forming agent forms a protective film on the metal film during polishing, thereby suppressing over-polishing that may occur in the circuit wiring, such as dishing and erosion, while maintaining a high polishing rate, thereby promoting a high level of planarization.

[0052] The film-forming agent contained in the polishing solution for making transparent of the present invention can be a compound having a triazole skeleton, a compound having an imidazole skeleton, a compound having a pyrimidine skeleton, a compound having a guanidine skeleton, a compound having a thiazole skeleton, a compound having a pyrazole skeleton, etc., and examples of the compound having a triazole skeleton include 1,2,4-triazole, 1,2,3-triazole, benzotriazole, 5-methylbenzotriazole, etc., and examples of the compound having an imidazole skeleton include imidazole, benzimidazole, etc., and examples of the nitrogen-containing cyclic compound having amino, imino, or mercapto can be mentioned. Among these, a triazole skeleton is particularly preferred.

[0053] Regarding the content of the film-forming agent, it is possible to add up to 2 mass% of the total amount of the clarifying polishing liquid, particularly from the viewpoint of maintaining and improving processing efficiency in terms of polishing speed, etc., and preventing over-polishing and corrosion, without being involved in making the polishing liquid transparent.

[0054] <About water> The water contained in the polishing solution for polishing transparency of the present invention acts as a dispersion medium or solvent for dissolving or dispersing each component. Examples of water include ion-exchanged water and ultrapure water, and ultrapure water is preferred from the viewpoint of both suppressing overpolishing and corrosion and improving the polishing rate. The content of water in the polishing solution of the present invention can be, for example, the remainder of silica particles, additives, complexing agents, film-forming agents, and other components.

[0055] <Other optional ingredients contained in the transparent polishing liquid> The polishing liquid for polishing polishing for polishing polishing powder ...

[0056] The pH adjuster is contained to adjust the pH of the clearing polishing liquid to a desired level, thereby enabling the liquid to exhibit a chemical polishing action such as etching, a mechanical polishing action by silica particles, or both polishing actions.

[0057] For example, within the pH range of 5 to 9, a good balance of chemical polishing and mechanical polishing is achieved. The pH adjuster and the pH value do not affect the transparency of the clarifying polishing solution, but can be set primarily from the perspective of manufacturability, such as the polishing speed, processing accuracy for the polishing process, and quality. By adjusting the function and performance of the polishing solution using a pH adjuster, it is possible to achieve high polishing performance and improved polishing speed while suppressing overpolishing and corrosion.

[0058] The pH can be adjusted using an acid component such as an inorganic acid (e.g., phosphoric acid, boric acid, etc.) or an organic acid, or an alkaline component such as ammonia, potassium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, or alkanolamine. A buffer solution containing a buffering agent may also be used to stabilize the pH. Examples of such buffer solutions include acetate buffer solutions, neutral phosphate buffer solutions, borate buffer solutions, and phthalate buffer solutions.

[0059] By adding water-soluble polymers and surfactants to the polishing liquid, the liquid properties such as viscosity, surface tension, and adsorption / repulsion are affected, and the polymers and surfactants are adsorbed onto the particle interfaces of the abrasive grains and the interlayer insulating film layer, thereby suppressing overpolishing and corrosion, while ensuring high polishing properties and appropriately adjusting the polishing rate with the polishing liquid.

[0060] Examples of water-soluble polymers include polyacrylic acid polymers such as polyacrylic acid, polyacrylic acid copolymers, polyacrylates and polyacrylic acid copolymer salts; polymethacrylic acid polymers such as polymethacrylic acid and polymethacrylates; polysaccharides such as carboxymethyl cellulose, agar, dextrin and cyclodextrin; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; and polyethylene glycol.

[0061] Regarding surfactants, examples of nonionic surfactants include polyoxypropylene polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxypropylene glyceryl ethers, polyoxyethylene glyceryl ethers, polyoxyethylene polyethylene glycols, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyglycerin fatty acid esters, and polyoxyethylene alkylamines. Examples of anionic surfactants include alkylbenzenesulfonic acids or salts thereof, and alkylnaphthalenesulfonic acids or salts thereof. Suitable salts include sodium salts and ammonium salts.

[0062] <About the transparent polishing solution> The characteristics of the clarifying polishing solution containing the above components will be described below.

[0063] The light transmittance of the clarifying polishing solution is in the range of 60% to 100%. This light transmittance is set by preparing the additive containing a polyol compound and approximating the refractive index between the solvent component containing the additive and the silica particles. If the light transmittance of the polishing solution is less than 60%, the polishing solution becomes cloudy, making it difficult to detect and determine the end point of polishing on the wafer surface during the polishing process.

[0064] The refractive index of the clarifying polishing liquid when the light transmittance is in the above range is in the range of 1.400 to 1.460 at 25° C. Furthermore, in order to obtain a polishing liquid with a higher light transmittance within this range, the refractive index is preferably in the range of 1.410 to 1.450.

[0065] The transparent polishing solution also ensures light transmittance in the wavelength range of 300 nm to 800 nm. As a result, this polishing solution transmits light from a portion of the ultraviolet range to the visible light range, allowing various light sources to be selected from a wide range of wavelengths for detecting and determining the polishing endpoint. The detection and determination of the polishing endpoint will be explained in detail later.

[0066] <Suitable forms for applying the clearing polishing liquid> The process of detecting and determining the polishing end point to which this polishing liquid can be applied, and the circuit wiring production process in which this polishing liquid can be suitably used will be described.

[0067] The detection and determination of the polishing endpoint is carried out optically (hereinafter also referred to as "optical polishing endpoint determination process"). Specifically, with the wafer fixed in the CMP polishing device, light is irradiated onto the surface to be polished of the wafer through the polishing liquid in parallel with the polishing process, and the state of the surface to be polished, such as the film thickness, is monitored based on the reflected light.

[0068] As an example, the above-mentioned CMP polishing apparatus includes a fixing means for placing a wafer on it, a rotating surface plate on which a polishing pad is placed, a polishing liquid supplying means for supplying a polishing liquid between the surface of the wafer to be polished and the polishing pad, and an optical monitor / determination means having a light irradiating means and an optical sensor for irradiating light onto the wafer surface and detecting the reflected light, and measuring or observing the polishing state based on the detection results, and detecting and determining the polishing end point.

[0069] Regarding the vertical positional relationship of each part, from the fixing means arranged at the top to the bottom, the wafer placed on the fixing means, the polishing pad, the rotating surface plate on which the polishing pad is placed, and the light irradiation means and the optical sensor are arranged below the surface plate. The polishing liquid supply means is installed in a position where it can supply the polishing liquid between the polishing pad and the surface to be polished.

[0070] Specifically, the method for detecting and determining the polishing end point involves placing a wafer on a holding means with the surface to be polished facing a polishing pad placed on a rotating platen. The holding means then moves the wafer closer to the rotating platen, pressing it against the polishing pad while the rotating platen rotates. At this time, a polishing liquid is supplied between the polishing pad and the surface to be polished by a polishing liquid supply means, and the CMP polishing process is performed.

[0071] The polishing pad is provided with a transparent observation window through which the polished surface can be visually observed. Light is irradiated onto the polished surface through this observation window, and the reflected light is detected by an optical sensor. The film thickness is measured based on the distance from the polished surface calculated based on the reflected light. The polishing endpoint is then detected and determined based on the measured film thickness.

[0072] Here, since the polishing liquid of the present invention is a transparent liquid, it is possible not only to measure the film thickness but also to detect and determine the polishing end point by photographing the state of the polished surface by irradiating it with light.

[0073] In the optical polishing endpoint determination process using the clarifying polishing liquid of the present invention, the optical monitor determination means includes, in addition to the light irradiation means and optical sensor, an imaging means such as a high-resolution camera or a microscope camera for imaging the polished surface of the wafer. This imaging means photographs the polished surface when the light irradiation means irradiates the polished surface with light while the clarifying polishing liquid is supplied between the polished surface of the wafer and the polishing pad during the CMP polishing process, and the displayed image can be monitored. In this case, an external monitor means such as a display may be connected to this imaging means, and the polished surface may be monitored externally via remote communication, the Internet, or the like.

[0074] Furthermore, regarding the monitoring method, since the polished surface is constantly displayed due to the transparent polishing liquid, it is possible to monitor the captured image in real time. Alternatively, the captured image of the polished surface can be collected by the imaging means, and the polishing endpoint can be detected and determined by image analysis, such as analyzing the image. Note that even in this optical polishing endpoint determination process, a film thickness measurement means may be provided in the CMP polishing apparatus so that processing based on film thickness measurement or processing that uses the measurement in combination can be performed.

[0075] Suitable examples of the light irradiation means, light sensor, and imaging means include a high-resolution camera equipped with a CCD image sensor or a CMOS image sensor, a microscope camera, etc. In image analysis, for example, to determine the polishing endpoint, methods using equipment equipped with software that recognizes images, automatically digitizes, extracts, imports, edits, and classifies them, or automatic determination using AI technology in the same equipment can be used.

[0076] The polishing pad used in this optical polishing endpoint determination process may be a general nonwoven fabric, foam, non-foam, etc. The polishing pad may be made of a resin such as polyurethane, polyester, polytetrafluoroethylene, polypropylene, polyethylene, acrylic elastomer, polyvinyl alcohol, cellulose, polyamide, or epoxy resin. It is preferable that the surface of the polishing pad is grooved.

[0077] The observation window (window material) of the polishing pad is made of a thermoplastic, thermosetting, or ultraviolet-curable resin or glass having optical transparency. Alternatively, a polishing pad made of a transparent resin having optical transparency may be used. Examples of the transparent resin having optical transparency include non-yellowing polyurethane.

[0078] The light transmittance of the clarifying polishing solution can be changed by adjusting the content of silica particles and additives within a range of 60% to 100%. For example, when the content of silica particles is small, the adjustment range by adding additives is large, so a clarifying polishing solution with a higher light transmittance can be adjusted. Note that when the content of silica particles is high, for example, when there is a limit on the content of additives to ensure processability, flatness, etc., the content will be small, and the light transmittance of the clarifying polishing solution will be low.

[0079] For example, when the content of silica particles is reduced to 1.0% by mass to 5.0% by mass or 1.0% by mass to 4.0% by mass, compared with the content of silica particles in the range of 0.1% by mass to 7.0% by mass, the content of additives can be adjusted to ensure processability and flatness while maintaining higher transparency. Note that even when the content of silica particles is 5.0% by mass or more, the content of additives can be adjusted to ensure the transparency of the polishing liquid.

[0080] The oxidizing agent content is adjusted to a range of 0.1% to 2.5% by mass based on the total amount of the clarifying polishing liquid to prevent the polishing liquid from becoming cloudy. The complexing agent and film-forming agent can be adjusted to a range of 0.01% to 20% by mass and 0.001% to 2% by mass, respectively, based on the total amount of the polishing liquid to obtain high processability and flatness without affecting transparency. Water is added as the balance of the other ingredients.

[0081] Incidentally, there are various methods for determining the polishing end point of a surface to be polished, such as a determination process based on a change in torque due to friction with a polishing pad, a process using eddy current measurement due to metal particles during polishing, etc. In particular, a process using eddy current measurement is generally used for determination process for polishing a metal film layer such as a circuit wiring generation process described later, but there is room for improvement in the determination process, such as the influence of scraped metal particles on the detection accuracy of electrical signals.

[0082] In the above situation, the transparent polishing solution of the present invention monitors the polishing state of the surface to be polished by light irradiation in parallel with the polishing process, including film thickness measurement, without relying on the behavior of electrical signals during polishing by metal particles, etc. As a result, this optical polishing endpoint determination process can be suitably used in the metal film layer generation process, and based on the results of monitoring the polishing state in the actual state, it is possible to avoid the influence of metal particles during polishing and ensure highly accurate detection and determination of the polishing endpoint.

[0083] Furthermore, since this clarifying polishing solution has the ability to transmit light in the wavelength range from part of the ultraviolet range to the visible light range, it can be monitored with light of a wide range of wavelengths. Furthermore, for example, by combining it with existing film thickness measurements, it becomes possible to perform more accurate judgment processing, such as taking into account the wafer thickness direction in relation to the shape of the circuit wiring pattern.

[0084] Next, we will explain the circuit wiring generation process in which the transparency polishing liquid can be suitably used in semiconductor manufacturing. First, the semiconductor manufacturing process consists of a front-end process for manufacturing wafers and a back-end process for assembling and inspecting the manufactured wafers. The front-end process mainly consists of a bare wafer processing and cleaning process for cutting wafers from silicon, a film formation process, a lithography and etching process, an ion implantation process, an interlayer insulating layer generation process for forming an insulating layer that electrically insulates circuit elements and circuit wiring, a circuit wiring generation process, and an inspection process. The processes are carried out in this order, or in some cases, a process may be repeated by returning to the previous process once or multiple times.

[0085] Among these, in the circuit wiring generation process, a trench pattern and contact holes for circuit wiring are formed on the interlayer insulating layer generated in the interlayer insulating layer generation process, and a metal film of circuit wiring material is deposited in the trench pattern and contact hole to generate a layer on which circuit wiring is formed (hereinafter, sometimes referred to as a "circuit wiring layer"). In this process, interlayer insulating layer generation, trench pattern formation, metal film deposition, and circuit wiring formation are sequentially repeated multiple times on the formed circuit wiring layer, and a three-dimensional circuit wiring layer is generated by stacking the formed circuit wiring layers.

[0086] In the circuit wiring generation process, CMP polishing is performed to remove excess metal film deposited on the interlayer insulating layer other than in the trench pattern and contact holes when generating the circuit wiring layer, and to flatten the surface of this circuit wiring layer.

[0087] In the CMP polishing process in the circuit wiring generation process, since the circuit wiring layer is formed of a metal circuit material on an interlayer insulating layer, polishing is performed on surfaces made of different materials: the oxide or nitride film that forms the interlayer insulating layer, and the metal for the circuit wiring. Since the surface resistance of these materials differs when polished, the polishing solution used in this polishing process, unlike other processes, is adjusted taking into account the differences in material properties such as hardness and solubility in the chemical solution of these materials, and based on these material properties, so as to effectively exert the effects of both mechanical polishing and chemical polishing.

[0088] Furthermore, in the circuit wiring generation process, a metal film for a barrier layer is generated between the metal film for circuit wiring and the insulating film layer when generating the circuit wiring layer to prevent the metal from diffusing into other layers. Specifically, first, the trench pattern on the interlayer insulating layer and the surrounding layer surfaces are covered with a layer of metal for the barrier layer, and then the metal for the circuit wiring is deposited on top of that. Then, by CMP polishing, the excess metal for circuit wiring and the metal for the barrier layer deposited outside the trench pattern are removed in this order, generating a circuit wiring layer with a barrier layer.

[0089] As mentioned above, because circuit wiring layers are made of different metals, the CMP polishing process must take into account differences in material properties such as hardness and the simultaneous processing of these metals. Furthermore, when circuit wiring layers are stacked to create a multilayered three-dimensional structure in this process, if each circuit wiring layer before creation lacks flatness, for example, due to significant surface undulations, surface roughness, or uneven layer thickness, the multilayered three-dimensional structure may not have the required thickness or may be distorted or irregular, potentially affecting the electrical characteristics of the semiconductor device. In the CMP polishing process, it is important to ensure high flatness by avoiding over-polishing or scratches on the polished surface while taking into account the differences in the materials mentioned above.

[0090] The transparent polishing solution of the present invention contains silica particles, an additive containing a polyol compound, an oxidizing agent, a complexing agent, and a film-forming agent, and therefore can perform a good polishing process for forming a circuit wiring layer having a metal film. Furthermore, by containing the above-mentioned additives, the transparent polishing solution has an effect of lowering the polishing performance for the metal for the circuit wiring compared to that for the barrier layer.

[0091] The transparency polishing liquid of the present invention produces different polishing rates depending on the material of the metal to be polished. In this polishing liquid, when the metal to be polished is a metal for circuit wiring and a metal for a barrier layer, increasing the content of additives causes a greater decrease in the polishing rate for the metal for circuit wiring than for the barrier layer. Furthermore, it was found that the decrease in the polishing rate for the metal for circuit wiring is greater than that for the barrier layer, while the change in the polishing rate for the metal for the barrier layer before and after adjusting the content of additives is small, and the decrease in the polishing rate is also small. In other words, by including the above-mentioned additives in the transparency polishing liquid, it is possible to selectively decrease the polishing performance for the metal for circuit wiring.

[0092] Regarding the above-mentioned effect, according to the inventor's intensive research, the polyol compound contained in the additive has the effect of reducing the corrosion current that can occur in the metal film on the wafer surface during CMP polishing, in addition to the aforementioned wettability and dispersibility. This is thought to be because it reduces the chemical polishing action of the silica particles, such as oxidation of the metal film by oxidizing agents and complexing agents and ionization of the metal.

[0093] Furthermore, metal materials for circuit wiring are subject to the above-mentioned chemical polishing action by CMP to a much greater extent than those for barrier layers, but it is presumed that the polishing action is suppressed by the polyol compound contained in the additive, resulting in a lower amount of polishing and a greater decrease in the polishing rate compared to metals for barrier layers.

[0094] When a transparency polishing solution is used to polish metal for a barrier layer while suppressing polishing performance for metal for circuit wiring, if the silica particle content is in the range of 0.1% by mass to 7.0% by mass, the additive content can be in the range of 55% by mass to 75% by mass, ensuring transparency. Furthermore, to achieve high transparency while maintaining processability and flatness, the additive content is preferably 60% by mass to 70% by mass. In this case, the silica particle content is preferably 1.0% by mass to 6.5% by mass, and more preferably 1.0% by mass to 6.0% by mass to achieve higher light transmittance.

[0095] On the other hand, when increasing the polishing speed and improving the polishing performance for the metal for the circuit wiring together with the barrier layer, the content of silica particles can be increased within the above range and CMP polishing can be performed. In this case, the additive contained can prevent over-polishing and scratches on the wafer surface even when the amount of silica particles is increased, and good flatness can be ensured. This is also effective when polishing the metal for the circuit wiring together with the barrier layer.

[0096] Regarding other components, in the transparentizing polishing solution of the present invention, the content of the film-forming agent is adjusted to a range of 0.001% by mass to 2% by mass relative to the total amount of the transparentizing polishing solution, thereby making it possible to adjust the polishing rate for the metal for circuit wiring while ensuring the polishing rate for the barrier layer. For example, by increasing the content of the film-forming agent in the transparentizing polishing solution, the polishing rate for the metal for circuit wiring decreases while suppressing the decrease in the polishing rate for the barrier layer.

[0097] Furthermore, when the content of silica particles is increased, increasing the content of the film-forming agent while blending an additive can mitigate the sudden increase in the polishing rate for the metal used for circuit wiring, and more effectively prevent overpolishing, scratches, etc.

[0098] An example of a polishing method using a transparentizing polishing solution in a circuit wiring process and an optical polishing endpoint determination process will be described. Note that the method of placing a wafer in a CMP polishing apparatus is the same as that described above.

[0099] A wafer coated with metal films for circuit wiring and a barrier layer is placed in a CMP polishing apparatus. A transparency polishing solution containing a predetermined amount of each component is then supplied onto a rotating polishing pad, and the wafer is pressed onto the polished surface, so that the polished surface is constantly in contact with the transparency polishing solution. There are no particular limitations on the pressure with which the wafer is pressed or the rotation speed of the polishing pad; values ​​within a range based on general processing conditions, etc., are used, depending on the specifications and quality required for the wafer.

[0100] In parallel with the CMP polishing process, the polished surface of the wafer is irradiated with light through the observation window and the clearing polishing solution by the optical monitor judgment means of the polishing apparatus, and the state of the polished surface is photographed and monitored sequentially. When it is judged that the state of the polished surface, such as the circuit wiring pattern on the polished surface, including the width of the circuit wiring, the spacing between each circuit wiring, and the presence or absence of a metal barrier layer between the circuit wiring, satisfies predetermined conditions, the polishing process is terminated.

[0101] Regarding the light irradiation means, since the clarifying polishing liquid transmits light from a part of the ultraviolet region to the visible light region, various light sources can be selected and used.

[0102] Wafers to which the clarification polishing solution can be applied include silicon wafers, glass substrates for TFT-LCDs, and substrates made of compound semiconductors such as GaN and GaAs. Metal materials for circuit wiring laminated on the wafer include copper (Cu), copper alloys, silver (Ag), silver alloys, cobalt (Co), ruthenium (Ru), aluminum (Al), aluminum alloys, tungsten (W), tungsten alloys, or oxides of these metals, or metals containing small amounts of impurities or additive elements.

[0103] Metals for the barrier layer, which are dissimilar metal materials to the above-mentioned metal materials, can be applied to metals such as titanium, titanium nitride, tantalum, tantalum nitride, copper, tungsten, cobalt, ruthenium, aluminum, aluminum alloys such as aluminum / copper alloys, and various mixtures and combinations thereof.

[0104] <About the Clearing Polishing Kit> Another embodiment using a clarifying polishing liquid will be described. The above-mentioned clarifying polishing liquid is a polishing liquid made transparent by blending an additive, but in this embodiment, taking advantage of the fact that adding the additive to a polishing liquid containing silica particles makes it possible to make the polishing liquid transparent, this additive is used as a separate solution to make a polishing kit for a clarifying polishing liquid containing at least two types of solutions (hereinafter also referred to as a "clarifying polishing liquid kit").

[0105] The transparency polishing kit of the present invention is a polishing kit containing a first solution containing silica particles, an oxidizing agent, a complexing agent, and a film-forming agent, and a second solution containing an additive containing a polyol compound, and is used in a process for forming a metal film layer on a wafer surface, and the process is preferably a circuit wiring process.

[0106] Regarding the first solution of the transparency polishing solution kit, before proceeding to the polishing process, each chemical solution is removed from each container containing the compounded components and prepared to the specified content. The oxidizing agent is added before the polishing process begins. The content of each compounded component, such as silica particles and complexing agent, is the same as that of the transparency polishing solution. When preparing the first and second solutions by mixing them, they may be diluted with water as needed.

[0107] The first solution of the transparency polishing solution kit can further contain other components such as a pH adjuster, a water-soluble polymer, a surfactant, etc., as desired, as long as the effects of the first solution are not impaired. The first solution may also contain a small amount of a polyol compound. In this case, the content of the polyol compound is preferably 0.01% by mass or more and 5% by mass or less, taking into account processability such as polishing speed and the flatness of the wafer surface.

[0108] As an example of how to use the transparency polishing liquid kit, it can be used in the circuit wiring production process as follows: Before this process, the transparency polishing liquid kit is used to prepare a first polishing liquid using a first solution for polishing the metals for the circuit wiring and barrier layer, and a second polishing liquid made by mixing the first solution with a second solution to make it transparent, and the first polishing liquid and then the second polishing liquid are used in that order as the process progresses to perform the CMP polishing process.

[0109] Although the first polishing liquid is not made transparent, it maintains a higher polishing rate than the second polishing liquid while still ensuring sufficient polishing performance for the metals for the circuit wiring and the barrier layer. As a result, for example, when processability is important, it is possible to use the first polishing liquid for polishing the surface to be polished, mainly the metal for the barrier layer, at the final stage of the circuit wiring generation process, until the surface to be polished requires polishing.

[0110] To add a bit more about the polished surface mainly consisting of the metal for the barrier layer, at the end of the circuit wiring process, the polishing process progresses and the metal for the circuit wiring deposited in the trench pattern and the metal for the barrier layer covering the areas outside the trench pattern begin to appear on the same surface. In this state, the metal for the circuit wiring is polished together with the metal for the barrier layer, so it is necessary to avoid over-polishing, such as dishing, which removes more depth from the top surface of the trench pattern, or scratches on the insulating layer below due to excessive removal of the thinly deposited barrier layer, and to ensure precision in processing and careful consideration of fine features such as the width and spacing of the circuit wiring.

[0111] Therefore, in the final stage of the circuit wiring process, the barrier layer is primarily polished using a polishing liquid made transparent using the second polishing liquid, allowing for highly accurate polishing while monitoring the polished surface. Furthermore, the second polishing liquid selectively polishes the metal for the barrier layer while reducing its polishing performance for the metal for the circuit wiring, making it possible to perform highly accurate and detailed processing on the polished surface.

[0112] The polishing endpoint determination method for the circuit wiring production process using the transparency polishing kit is specifically described below. Note that the procedure for placing the wafer in the CMP polishing apparatus before polishing is the same as the method for using the transparency polishing kit.

[0113] A wafer placed in a CMP polishing apparatus is polished by being pressed against a rotating polishing pad supplied with a first polishing liquid, and the condition of the polished surface is successively detected by a sensor. When a predetermined condition is detected, the supplied polishing liquid is switched from the first polishing liquid to the second polishing liquid, and further, monitoring of the condition of the polished surface by an imaging means is started. As the polishing process with the second polishing liquid progresses, the captured image of the polished surface is monitored, and when it is determined that the polished surface has reached the predetermined condition, the polishing process is terminated.

[0114] The state of the polished surface when changing from the first polishing liquid to the second polishing liquid can be determined by known methods such as film thickness measurement or an eddy current detection method using metal powder produced by polishing. Similarly to the case of the transparentization polishing liquid, the endpoint of polishing using the transparentization polishing liquid kit can also be determined by real-time monitoring or image analysis using captured images.

[0115] <Example> The clarifying polishing liquid of the present invention will be described in detail below with reference to examples. Note that the following examples are merely illustrative examples for the purpose of understanding the polishing liquid, and the present invention is not limited to these examples.

[0116] <Preparation of the Clearing Polishing Solution (Clearing Polishing Solution of Examples 1 to 5)> For the polishing solution for making the surface transparent in each example, the additive was prepared and mixed into the polishing solution containing various components excluding the additive so that the light transmittance would be 60% or more. The components and their contents in the polishing solutions for making the surface transparent in each example are shown in Table 1.

[0117] The polyol compounds contained in the additives in each example were: glycerin (purified glycerin) manufactured by Sakamoto Pharmaceutical Co., Ltd. in Examples 1 and 2; polyglycerin having an average degree of polymerization of 4 and an average molecular weight of 310 ("Polyglycerin #310" manufactured by Sakamoto Pharmaceutical Co., Ltd.) in Example 3; polyglycerin having an average degree of polymerization of 10 and an average molecular weight of 750 ("Polyglycerin #750" manufactured by Sakamoto Pharmaceutical Co., Ltd.) in Example 4; and polyglycerin having an average degree of polymerization of 15 and an average molecular weight of 1100 (manufactured by Sakamoto Pharmaceutical Co., Ltd.) in Example 5. The silica particles were ultra-high purity colloidal silica synthesized by the sol-gel method; specifically, PL-7 (manufactured by Fuso Chemical Co., Ltd.), which is stable at a pH of neutral to alkaline, was used.

[0118] The light transmittance was measured using an absorptiometer (LAMBDA VISION SA100 series) at wavelengths from ultraviolet 220 nm to near infrared 800 nm, and the measured values ​​were used to calculate the light transmittance.

[0119] The refractive index of each of the transparentizing polishing solutions of Examples 1 to 5 was also measured, and the refractive index was 1.428 for Example 1, 1.435 for Example 2, 1.424 for Example 3, 1.427 for Example 4, and 1.429 for Example 5.

[0120] For all polishing solutions in the Examples, including the Comparative Examples described below, the haze value was also measured for reference, along with the light transmittance. The haze value was calculated by the following formula: haze value (%) = ((total light transmittance) - (parallel light transmittance)) / (total light transmittance) x 100, based on the measured values ​​of total light transmittance and parallel light transmittance when the polishing solution was irradiated with light. The smaller the haze value, the higher the transparency. The measuring instrument used was the NDH2000 (halogen lamp D65 light source, wavelength 380 nm to 780 nm, haze and total light transmittance measurement) manufactured by Nippon Denshoku Industries Co., Ltd.

[0121] The remaining components in Examples 1 to 5 are water and a pH adjuster. The pH adjuster was adjusted to 11 using potassium hydroxide.

[0122] The pH was measured at 25°C using three standard buffer solutions: phthalate pH buffer solution (pH 4.01 at 25°C), neutral phosphate pH buffer solution (pH 6.86 at 25°C), and borate pH buffer solution (pH 9.18 at 25°C). The electrode was then placed in the polishing solution and the pH was measured after stabilization for at least three minutes. The measuring instrument used was a Model F-54 manufactured by Horiba Ltd.

[0123] <Regarding the polishing solutions of Comparative Examples 1 to 3> The polishing liquids of Comparative Examples 1 to 3 are cloudy polishing liquids containing the same components as those of Examples 1 to 5. The content of each component is shown in Table 1. Regarding the polyol compound contained in the additives of each polishing liquid, glycerin, the same as in Example 1, was used in Comparative Example 2, and polyethylene glycol with an average molecular weight of 1,000 was used in Comparative Example 3. The polishing liquid of Comparative Example 1 does not contain any additives. Furthermore, the same silica particles as those of Examples 1 to 5 were used in Comparative Examples 1 to 3. Furthermore, as in Examples 1 to 5, water and a pH adjuster were contained as the balance other than the above components. The pH value was 11.

[0124] <Polishing conditions, polishing method, and method for monitoring the polishing process> Regarding the polishing conditions for the polishing solution in this example, the polishing device used was a desktop automatic polisher, Dialap AceML-160A (manufactured by Maruto Co., Ltd.), and the polishing pads used were a polyurethane IC1000TM with a highly uniform fine foam structure and a transparent observation window, and an IC1000XY-perforated nonwoven fabric with a continuous foam structure (manufactured by Nitta DuPont Co., Ltd.). The polishing pressure on the wafer surface to be polished was 4.77 psi, the head / platen rotation speed of the automatic polisher was 60 rpm, and the supply rate of the polishing solution was 12 ml / min.

[0125] The wafers used in Examples 1 to 5 and Comparative Examples 1 to 3 were copper metal film wafers and barrier metal film wafers. The copper metal film wafers were silicon substrates with thermal oxide films, on whose surfaces a copper film with a thickness of 1500 nm was formed. The barrier metal film wafers were silicon substrates with a tantalum (Ta) film with a thickness of 300 nm and a tantalum nitride (TaN) film with a thickness of 200 nm formed thereon.

[0126] The polishing process involved placing both the copper metal film wafer and the barrier metal film wafer in a polishing machine and supplying the polishing solution under the same polishing conditions. The polished surface was monitored by placing a camera under the rotating platen on which the polishing pad was placed and irradiating it with light, while capturing images of the polished surface through the opening in the rotating platen and the observation window in the polishing pad. The camera used was a system stereo microscope (Nikon SMZ18) equipped with a CMOS sensor, which allows for efficient image acquisition and is combined with a camera control unit for software, focal length, brightness adjustment, etc.

[0127] <Evaluation of polishing condition and polishing performance> The polishing condition was evaluated as follows. A condition in which there was almost no fluctuation of light due to the liquid phase of the polishing liquid relative to the amount of light projected from the observation window provided in the pad, and the wafer surface could be clearly observed, was rated as ◯ (good). Next, a condition in which there was little fluctuation of light due to the liquid phase of the polishing liquid relative to the amount of light projected from the observation window (window material) provided in the pad, and the wafer surface could be observed, was rated as △ (fairly good). Finally, a condition in which there was great fluctuation of light due to the liquid phase of the polishing liquid relative to the amount of light projected from the observation window (window material) provided in the pad, and the wafer surface could not or was difficult to observe, was rated as × (poor).

[0128] The polishing performance of the clearing polishing solution was evaluated by calculating the polishing rate during the polishing process. The polishing process was carried out for 1 minute under the above polishing conditions, and the polishing rate was calculated as follows: polishing rate (nm / min) = (film thickness before polishing - film thickness after polishing) / polishing time, based on the relationship between surface resistance and film thickness previously investigated and examined for the copper and barrier metal on the wafer surface used.

[0129] The results obtained in Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0130] [Table 1]

[0131] As can be seen from Table 1, the transparency polishing solutions of Examples 1 to 5 have higher light transmittance than the polishing solutions of Comparative Examples 1 to 3, at 60% or more, and it was therefore confirmed that the condition of the polished surface of both the metal copper film wafer and the barrier metal film wafer can be clearly monitored during the polishing process.

[0132] Regarding polishing performance, Table 1 shows that the polishing rates for metal copper film wafers and barrier metal film wafers are small for the transparent polishing solutions of Examples 1 to 5, similar to Comparative Example 1, which does not contain additives, but the amount of decrease is greater for metal copper film wafers than for barrier metal film wafers.

[0133] The transparency polishing solution of Example 2 shows a case where the colloidal silica content is increased compared to Example 1. In this case, Table 1 shows that the polishing rate using the transparency polishing solution of Example 2 relative to Example 1 is higher for the metal copper film wafer than for the barrier metal film wafer. Furthermore, the transparency polishing solution of Example 3 shows a case where the benzotriazole content is increased compared to Example 1. In this case, Table 1 shows that a decrease in the polishing rate is observed for both the metal copper film wafer and the barrier metal film wafer, but the amount of decrease is greater for the metal copper film wafer than for the barrier metal film wafer.

[0134] As shown in Table 1, it was confirmed that the transparency polishing solutions of Examples 1 to 5 can selectively change the polishing rate depending on the type of metal film on the wafer, allowing the polishing process to be carried out while clearly monitoring the polishing state during the polishing process. [Industrial Applicability]

[0135] The transparent polishing solution of the present invention has high polishing performance and allows the polishing process to be performed while directly and clearly observing the polishing state, making it possible to determine the polishing endpoint. This transparent polishing solution can also meet the high demands for wafer surface flatness, etc., that accompany the current trend toward higher integration, multi-layering, and miniaturization of semiconductor elements, and is particularly suitable for use in processes for forming metal layers on wafers, such as circuit wiring processes.

[0136] Furthermore, SiC and GaN are attracting attention as next-generation semiconductor materials in industries requiring large amounts of power, such as power generation and transmission systems, automobiles, information and communication devices, and industrial robots. While SiC and GaN are thermally and chemically stable, they are also highly hard and extremely difficult to process, and therefore require a high degree of flatness for processing. The clarifying polishing solution of the present invention is particularly expected to be applicable to the above-mentioned processing, as it has optical transparency over a wide wavelength range.

Claims

1. The polishing liquid is a clarified polishing liquid containing silica particles and an additive containing a polyol compound selected from glycerin or polyglycerin having an average degree of polymerization of 1 to 20, and in which the refractive index of the solvent containing the additive is made close to the refractive index of the silica particles, and the clarified polishing liquid has a function of adjusting the mechanical polishing force of the silica particles and is used to optically detect the polishing end point.

2. 2. The clarifying polishing liquid according to claim 1, wherein the light transmittance of the clarifying polishing liquid is 60% or more.

3. 3. The polishing liquid for making transparent according to claim 1, wherein the wavelength of light transmitted through the polishing liquid for making transparent is 300 nm to 800 nm.

4. 3. The polishing solution for making the wafer transparent according to claim 1, which contains an oxidizing agent, a complexing agent, and a film-forming agent, and is used in a process for forming a metal film on the wafer surface.

5. 4. The polishing solution for making the wafer transparent according to claim 3, which contains an oxidizing agent, a complexing agent, and a film-forming agent, and is used in a process for forming a metal film on the wafer surface.

6. A polishing method using a transparent polishing liquid, which contains silica particles and an additive containing a polyol compound selected from glycerin or polyglycerin having an average degree of polymerization of 1 to 20, and in which the refractive indexes of the silica particles and the additive are made close to each other, is characterized by using a transparent polishing liquid to polish a wafer surface while monitoring the polished surface of the wafer surface through the transparent polishing liquid, thereby detecting and determining the polishing end point.

7. A polishing method using a transparent polishing liquid as described in claim 6, characterized in that light is irradiated onto the polished surface of the wafer surface to monitor the polished surface, and the wavelength of the light at this time can be adjusted within the range of 300 nm to 800 nm.

8. A polishing method using a transparent polishing liquid as described in claim 6 or 7, characterized in that in the process of forming a metal film on the wafer surface, the polished surface is monitored while removing excess metal film formed on the wafer surface, and the polishing end point is detected and determined.

9. A polishing liquid kit for a transparent polishing liquid, comprising a first solution containing silica particles, an oxidizing agent, a complexing agent, and a film-forming agent, and a second solution containing an additive containing a polyol compound selected from glycerin and polyglycerin having an average degree of polymerization of 1 to 20, the kit being used in a process of forming a metal film layer on a wafer surface.

10. A polishing method using a polishing liquid kit for a transparent polishing liquid, as described in claim 9, characterized in that a polishing process of a metal film layer is performed using a first polishing liquid using the first solution, and after the state of a specified polished surface is detected, the polishing process is performed by switching to a second polishing liquid mixed with the second solution, and the polishing process is performed while monitoring the polished surface, and the polishing end point is detected and determined.

Images