Manufacturing method of polished workpiece

Abstract

To improve a polishing speed.SOLUTION: A manufacturing method is for obtaining a polishing workpiece by polishing a polishing object with a molding board. In the manufacturing method, at first, a first polishing liquid that contains chitosan grains carrying an inorganic material and that is prepared to be pH5.8 or more is supplied to the molding board, and polishing object is polished by the molding board. Next, a second polishing liquid prepared to be pH5.0 or less is supplied to the molding board where the chitosan grains exist, and the polishing object is further polished by the molding board. As mentioned above, the polishing by the first and second polishing liquid is performed to obtain the polishing workpiece.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a polished workpiece. [Background technology]

[0002] To fabricate semiconductor devices, wafers must be planarized to atomic-scale surface roughness. Conventional wafer planarization is generally performed through four processes: primary mechanical polishing, secondary mechanical polishing, primary chemical mechanical polishing, and secondary chemical mechanical polishing. For example, a different platen is used for each process, such as using a cast iron platen for primary mechanical polishing, a tin platen for secondary mechanical polishing, a hard pad for primary chemical mechanical polishing, and a soft pad for secondary chemical mechanical polishing.

[0003] For example, the method disclosed in Patent Document 1 comprises a polishing process consisting of a first step in which a slurry containing abrasive grains is dropped onto a resin pad to perform mechanical polishing, and a second step in which chemical mechanical polishing is performed using a colloidal silica aqueous polishing liquid with a resin or cloth pad. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-92155 Summary of the Invention [Problem to be solved by the invention]

[0005] In the chemical mechanical polishing process, if the slurry used in the previous mechanical polishing process remains on the platen, it can cause deep scratches on the wafer, hindering planarization. Therefore, after mechanical polishing is completed, it is necessary to stop the polishing apparatus and replace the platen on which the slurry used in mechanical polishing remains, which leads to a decrease in the polishing rate. Similar issues as those in wafer polishing exist not only in the polishing of semiconductor wafers described above, but also in the polishing of optical materials such as lenses and ceramics, and there is a demand for improving the polishing rate.

[0006] The present invention has been proposed in view of the above-mentioned problems associated with the conventional technology in order to suitably solve these problems, and aims to provide a method for manufacturing a polished workpiece that can improve the polishing rate. [Means for solving the problem]

[0007] The first aspect of the method for manufacturing a polished product according to the present invention is as follows: a first polishing liquid containing chitosan particles carrying an inorganic material and adjusted to a pH of 5.8 or higher is supplied to a platen, and an object to be polished is polished on the platen; The gist of the method is that a second polishing liquid adjusted to a pH of 5.0 or less is supplied to the platen on which the chitosan particles are present, and the object to be polished is polished on the platen, thereby obtaining a polished product.

[0008] A second aspect of the method for manufacturing a polished product according to the present invention is the first aspect, the second polishing liquid contains a photocatalytic inorganic material; The second polishing liquid supplied to the platen may be irradiated with ultraviolet light.

[0009] A third aspect of the method for manufacturing a polished product according to the present invention is the first or second aspect, The surface plate may be the same for polishing with the first polishing liquid and polishing with the second polishing liquid.

[0010] A fourth aspect of the method for manufacturing a polished product according to the present invention is any one of the first to third aspects, The first polishing liquid may contain polysaccharide fiber.

[0011] A fifth aspect of the method for producing a polished product according to the present invention is any one of the first to fourth aspects, The second polishing liquid may contain polysaccharide fiber.

[0012] A sixth aspect of the method for producing a polished product according to the present invention is any one of the first to fifth aspects, The chitosan particles may be composed of uncrosslinked chitosan. [Effects of the Invention]

[0013] According to the method for producing a polished product of the present invention, the polishing rate can be improved. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a partially cutaway schematic view of a first abrasive according to the present invention. [Figure 2] 1 is a structural formula showing chitosan constituting the chitosan particles according to the present invention. [Figure 3] 1A to 1C are explanatory diagrams showing a manufacturing process of abrasive particles. [Figure 4] 1A to 1C are explanatory diagrams showing a manufacturing process of abrasive particles. [Figure 5] 1 is a photograph of the abrasive particles of Example 1 taken with a scanning electron microscope at a magnification of 1300 times. [Figure 6] 1 is a schematic side view showing a polishing apparatus according to an embodiment of the present invention; [Figure 7] 1 is a schematic plan view showing a polishing apparatus according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0015] (Outline of manufacturing method for polished workpiece) The method for producing a polished product according to the present disclosure involves polishing a polished object using a first polishing liquid containing a first abrasive having chitosan particles as a matrix (carrier), and then polishing the polished object using a second polishing liquid having a lower pH than the first polishing liquid. The pH of the second polishing liquid is set to an acidic range in which the chitosan particles dissolve. The second polishing liquid preferably contains a second abrasive. Here, the polishing step in which the first polishing liquid is supplied is referred to as the first polishing step, and the polishing step in which the second polishing liquid is supplied is referred to as the second polishing step. The first polishing step can be primarily performed as a lapping step and may be either mechanical polishing without chemical action or chemical mechanical polishing with chemical action. The second polishing step can be primarily performed as a polishing step and may be either mechanical polishing without chemical action or chemical mechanical polishing with chemical action. However, to precisely mirror-finish the polished object, the second polishing step is preferably chemical mechanical polishing. The degree of polishing can be adjusted appropriately depending on the type of object to be polished, for example, by performing lapping through the first polishing step and the second polishing step, or by performing polishing through the first polishing step and the second polishing step.

[0016] The second polishing step may be started after the first polishing step is completed, such that the supply of the second polishing liquid is started after the supply of the first polishing liquid is stopped, or the first polishing step and the second polishing step may overlap for a part of the time, such that the supply of the second polishing liquid is started while the first polishing liquid is being supplied and then the supply of the first polishing liquid is stopped. Note that, from the viewpoint of improving the polishing rate, it is preferable to start the supply of the second polishing liquid after the supply of the first polishing liquid is stopped.

[0017] (1st polishing liquid) The first polishing liquid used in the first polishing step contains a first abrasive containing at least chitosan particles carrying an inorganic material (hereinafter referred to as abrasive particles). In the first polishing liquid, the first abrasive is dispersed in a first dispersion medium. The first abrasive may consist solely of abrasive particles or may contain abrasive particles other than abrasive particles. Abrasive particles other than abrasive particles may include those used in lapping, such as diamond, silicon carbide, and alumina (aluminum oxide). When the first abrasive consists solely of abrasive particles, the polishing rate can be improved by eliminating the need to remove abrasive particles other than abrasive particles and by using the same surface platen in the first polishing step as in the second polishing step. The first polishing liquid is adjusted to a pH range in which the chitosan particles can maintain their particle shape.

[0018] (abrasive particles) As shown in FIG. 1 , the abrasive particles according to the present disclosure comprise chitosan particles and an inorganic material supported on the chitosan particles. The chitosan constituting the chitosan particles has a positive surface charge over a certain pH range (pH 2 to 10) when dispersed in a liquid (aqueous or organic) medium. The inorganic material constituting the abrasive particles has a negative surface charge when dispersed in a medium having a predetermined pH at which the chitosan constituting the chitosan particles has a positive surface charge. The abrasive particles have a large number of inorganic materials attached to the chitosan particles by electrostatic interaction. The inorganic materials can be arranged in various ways in the abrasive particles, such as only on the surface of the chitosan particles, only inside the chitosan particles, or both inside and on the surface of the chitosan particles. Here, it is preferable for the inorganic material to be on the surface of the chitosan particles, since this allows for efficient polishing of the object to be polished.

[0019] The degree of inorganic material coverage on the surface of chitosan particles can be adjusted by the amount of inorganic material added, and for example, the inorganic material can be packed tightly onto the surface of chitosan particles. The abrasive particles can be so-called core-shell particles, in which an inorganic material is arranged as a shell covering a chitosan particle as a core (base material). The abrasive particles can also be porous chitosan particles with pores on the surface, in which case an inorganic material can be arranged on the pore wall surfaces forming the pores of the chitosan particles. The abrasive particles can be spherical or nearly spherical.

[0020] In the following description, the surface charge (zeta potential) is measured using a laser Doppler zeta potential measuring device. The surface charge refers to the polarity of the peak value of the zeta potential in a liquid medium prepared in a specific pH range. The zeta potential is an index that indicates the degree of charge on the particle surface. However, since the zeta potential varies depending on the pH of the liquid medium in which the particles are dispersed, in this disclosure, the zeta potential is expressed as a value measured in a liquid medium prepared in a pH range of 2 to 10.

[0021] In abrasive particles, the surface charge of the inorganic material carried by the chitosan particles is neutralized between the chitosan and the inorganic material, resulting in a zero surface charge. If 100% of the inorganic material is adsorbed to the amino groups of the chitosan in the chitosan particles, the surface charge of the chitosan will be zero. If 100% of the inorganic material is not adsorbed to the amino groups of the chitosan in the chitosan particles (the amount of inorganic material is less than the amount of amino groups), the surface charge of the chitosan particles (abrasive particles) is considered to be positive.

[0022] (average particle size of abrasive particles) The particle size of the abrasive particles can be adjusted as desired as described below, but they are preferably micro-sized particles with an average particle size of 1 mm or less. Specifically, the average particle size of the abrasive particles is preferably in the range of 5 μm to 800 μm, and more preferably in the range of 10 μm to 500 μm. Having the above-mentioned average particle size makes the abrasive particles convenient when added to other materials such as resins. Note that the average particle size in this disclosure is measured using flow image analysis and a scanning electron microscope (SEM).

[0023] In particular, the average particle size of the abrasive particles is preferably in the range of 5 μm to 300 μm, and more preferably in the range of 30 μm to 100 μm. When the abrasive particles have an average particle size in the above-mentioned range, the settling rate of the abrasive particles can be suppressed and the polishing rate can be improved. Note that, if the average particle size of the abrasive particles is small, it becomes difficult to increase the polishing rate, and if the average particle size of the abrasive particles is large, the settling rate of the abrasive particles in the first polishing liquid becomes high, making it difficult to increase the polishing rate.

[0024] (Ratio of chitosan particles to inorganic material in abrasive particles) The abrasive particles preferably contain 1 wt% to 500 wt% of inorganic material relative to the chitosan particles, more preferably 2 wt% to 400 wt%. When the ratio of inorganic material to chitosan particles is within the above range, the surface of the chitosan particles can be adequately covered with the inorganic material, resulting in so-called core-shell particles. Note that if the ratio of inorganic material to chitosan particles is low, the functions derived from the inorganic material tend to be difficult to exhibit, while if the ratio of inorganic material to chitosan particles is high, the functions derived from the inorganic material tend to be easily exhibited, but the inorganic material tends to be difficult to support on the chitosan particles.

[0025] (Chitosan particles) Chitosan particles are composed of chitosan as shown in Figure 2. Chitosan has a rigid structure due to hydrogen bonds, but when acid is applied, the molecular chains spread due to the charge repulsion of the amino groups, causing the chitosan to dissolve. At this time, the chitosan is positively charged. Chitosan particles preferably have a positive surface charge in a medium with a pH of 9 or less. Chitosan only needs to have a negative surface charge in the dispersion liquid (acid aqueous solution) described below that is used in the process of compounding with inorganic materials. In this way, chitosan particles have a positive surface charge, which allows them to incorporate inorganic materials with a negative surface charge.

[0026] (Deacetylation rate of chitosan) The chitosan shown in Figure 2 may be, for example, a deacetylated chitin product or a partially deacetylated chitin product, or a derivative thereof. The deacetylation rate of chitosan is preferably in the range of 50% to 100%, more preferably in the range of 80% to 100%. When the deacetylation rate of chitosan is in the above range, the number of amino groups (see Figure 2) increases, resulting in an increased number of charged moieties, which is preferable because it improves the ability to retain inorganic materials.

[0027] (Molecular weight of chitosan) The chitosan particles are preferably composed of chitosan having a molecular weight in the range of 10,000 to 10,000,000, more preferably in the range of 10,000 to 500,000. Chitosan having a molecular weight in this range has an appropriate viscosity that makes it easily soluble in a solvent during the dropletization (particulation) process described below, and can be made into chitosan particles with an appropriate particle structure capable of supporting inorganic materials and a spherical or nearly spherical shape. Note that chitosan tends to have higher viscosity as the molecular weight increases, while it tends to be more difficult to maintain its particle structure as the molecular weight decreases.

[0028] (average particle size of chitosan particles) The particle size of the chitosan particles can be adjusted as desired, as described below, but they are preferably micro-sized particles with an average particle size of 1 mm or less. Since the abrasive particles are made of inorganic materials smaller than the chitosan particles, the size of the abrasive particles is largely determined by the size of the chitosan particles. Specifically, the average particle size of the chitosan particles is preferably in the range of 5 μm to 800 μm, and more preferably in the range of 10 μm to 500 μm. The aforementioned average particle size of the chitosan particles makes them suitable as a substrate for supporting inorganic materials.

[0029] (Presence or absence of cross-linked structure of chitosan) Chitosan that does not have a cross-linked structure is preferred. Chitosan that does not have a cross-linked structure is softer than chitosan that does have a cross-linked structure. By using abrasive particles whose base material is chitosan particles that do not have a cross-linked structure, the buffering effect of the elasticity unique to chitosan particles in the first polishing step can be used to avoid polishing defects such as deep scratches on the object to be polished. In addition, by using abrasive particles whose base material is chitosan particles that do not have a cross-linked structure, the chitosan particles are more easily dissolved in the second polishing liquid, thereby improving the removal speed of the abrasive particles.

[0030] (Chemical modification of chitosan) The chitosan particles may be partially or entirely chemically modified chitosan into which an appropriate functional group has been introduced. The chitosan can be chemically modified, for example, by reacting it with a compound having a functional group that reacts with the amino group of chitosan. The introduction of functional groups into chitosan can be carried out at any appropriate time, such as during the process of granulating chitosan or after it has been made into abrasive particles. When the chitosan particles are partially or entirely chemically modified, they can exhibit functions according to the chemical modification. The introduction of functional groups into chitosan during the process of granulating chitosan can reduce manufacturing steps and costs compared to when it is carried out after it has been made into abrasive particles.

[0031] For example, abrasive particles can be hydrophobized by introducing hydrophobic groups, such as long-chain alkyls or aromatics, into chitosan. Abrasive particles can be hydrophobized by reacting them with a hydrophobic compound containing functional groups reactive with the amino groups of chitosan. Such hydrophobic compounds include aldehyde compounds, carboxylic acid halides, carboxylic acid anhydrides, and isocyanates, each of which can be used alone or in combination. Hydrophobization of chitosan is possible either by adding a hydrophobic compound to an acid aqueous solution or dispersion during the chitosan dropletization process, or by adding a hydrophobic compound after the abrasive particles are collected. The advantage of hydrophobizing chitosan is that when the specific gravity of chitosan and inorganic materials is high (e.g., 1.5 or higher), the specific gravity can be reduced by introducing carbon atoms as hydrophobic groups into chitosan. This allows for proper dispersion of inorganic materials during the chitosan dropletization process, ensuring even distribution of the inorganic materials on the surface of the chitosan particles. Furthermore, the chitosan particles can be prevented from swelling or dissolving in water.

[0032] (Inorganic materials) The inorganic material is harder than chitosan particles and mainly functions as an abrasive grain in the polishing particles. The inorganic material is preferably one that has a negative surface charge in a medium of pH 10 or less. In this way, the inorganic material has a negative surface charge, so that it can be attached to chitosan particles that have a positive surface charge. Note that the inorganic material only needs to have a negative surface charge in the dispersion liquid (acid aqueous solution) described below that is used in the process of compounding with the chitosan particles. For example, it is preferable that the inorganic material has a negative surface charge in an acid aqueous solution prepared in the pH range of 2 to 6.

[0033] Examples of inorganic materials that can be used include single-crystal diamond, polycrystalline diamond, silicon carbide, silica, anatase-type titanium oxide, rutile-type titanium oxide, boron carbide, aluminum (III) oxide, zirconia, iron (II) oxide (FeO), triiron tetroxide (magnetite, Fe3O4), α-iron (III) oxide, β-iron (III) oxide, γ-iron (III) oxide, ε-iron (III) oxide, α-iron oxyhydroxide, β-iron oxyhydroxide, γ-iron oxyhydroxide, δ-iron oxyhydroxide, limonite, ferrihydrite, schwertmannite, graphite, chromium oxide, ceria (cerium oxide), gallium nitride, boron nitride, zinc oxide, tin oxide, manganese oxide, barium carbonate, calcium carbonate, magnesium carbonate, garnet, and clay minerals such as montmorillonite, bentonite, sericite, and mica. The inorganic materials can be used alone or in combination.

[0034] The inorganic material is selected appropriately depending on the object to be polished, and preferably has a negative surface charge in an aqueous solvent with a pH of 10 or less. Examples include single crystal diamond, polycrystalline diamond, silicon carbide (SiC), aluminum oxide, and boron carbide. The inorganic material preferably has a negative surface charge in the pH range of the first polishing liquid.

[0035] (average particle size of inorganic material) The average particle size of the inorganic material is smaller than that of the chitosan particles. The average particle size of the inorganic material can be selected depending on the function required of the abrasive particles, but is preferably in the range of 0.5 nm to 50 μm, more preferably 5 nm to 30 μm. When the average particle size of the inorganic material is within this range, it is easy to compound with chitosan particles, and when used as abrasive particles, the functions unique to the inorganic material can be properly exhibited. Note that when the particle size of the inorganic material is small enough to the molecular level, it becomes difficult to exhibit its function, and when the particle size is large, it tends to settle when compounded with chitosan particles, making compounding difficult.

[0036] (Method of manufacturing abrasive particles) Next, an example of a method for producing abrasive particles is described. First, a dispersion containing an organic solvent and an acid aqueous solution containing an inorganic material and chitosan dissolved therein is prepared (see FIG. 3(a)). For example, the inorganic material and the acid aqueous solution containing chitosan dissolved therein may be added to the organic solvent. The dispersion may optionally contain a thickener, which is added to the organic solvent to increase the viscosity of the dispersion. Next, the dispersion is stirred to form droplets of the acid aqueous solution (see FIG. 3(b)). The droplets formed at this stage contain the inorganic material distributed in the domains of the acid aqueous solution containing dissolved chitosan. Next, the dispersion is heated to evaporate water from the droplets of the acid aqueous solution (droplets) (see FIG. 4(a)). During this process, the dispersion is continuously stirred. As the water evaporates from the droplets, the chitosan particles solidify into spherical shapes, while the inorganic material remains distributed in the domains of the acid aqueous solution containing dissolved chitosan. This results in abrasive particles with the inorganic material supported on the chitosan particles (see FIG. 4(b)). The abrasive particles are then recovered by necessary treatment such as filtration and washing. The abrasive particles may be classified to make the particle size uniform.

[0037] (Aqueous acid solution) The acid solution used is one that can dissolve chitosan. Alternatively, an acid solution that does not dissolve inorganic materials can be used. Examples of such acids include water-soluble acids such as hydrochloric acid, nitric acid, L-lactic acid, D-lactic acid, L-malic acid, D-malic acid, acetic acid, propionic acid, butanoic acid, citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, gallic acid, salicylic acid, acrylic acid, and methacrylic acid. Among these, organic acids are preferred from the viewpoint of reducing environmental impact.

[0038] (Concentration of aqueous acid solution) The acid concentration in the aqueous acid solution is preferably in the range of 0.4 to 5.0 times, more preferably 0.8 to 2.0 times, the amino group equivalent of chitosan. By having the acid concentration in the aqueous acid solution within this range, it is possible to appropriately dissolve chitosan in the aqueous acid solution while suppressing hydrolysis of the main chain of chitosan. Note that, if the acid concentration in the aqueous acid solution is low, chitosan becomes less soluble, while if the acid concentration in the aqueous acid solution is high, hydrolysis of the main chain of chitosan tends to occur more easily.

[0039] (pH of aqueous acid solution) The pH of the aqueous acid solution is preferably in the range of 2 to 6. When the pH of the aqueous acid solution is in this range, the chitosan can be appropriately dissolved in the aqueous acid solution while suppressing hydrolysis of the main chain of the chitosan. Note that when the pH of the aqueous acid solution is high (on the neutral side), the chitosan becomes less soluble, and when the pH of the aqueous acid solution is low, the main chain of the chitosan tends to be more easily hydrolyzed.

[0040] (Ratio of chitosan to inorganic material in acid aqueous solution) In the acid aqueous solution, the inorganic material is preferably in the range of 0.5 wt% to 500 wt% relative to chitosan, more preferably in the range of 2 wt% to 400 wt%. When the ratio of inorganic material to chitosan in the acid aqueous solution is within this range, abrasive particles can be obtained in which the surfaces of chitosan particles are appropriately covered with inorganic material, and the abrasive particles can be so-called core-shell particles. Note that if the inorganic material is too little relative to the chitosan particles, the functions derived from the inorganic material tend to be difficult to exhibit, while if the inorganic material is more abundant relative to the chitosan particles, the functions derived from the inorganic material tend to be easily exhibited, but the inorganic material tends to be difficult to support on the chitosan particles.

[0041] (organic solvent) The organic solvent may be one that separates from water. It is preferable to use a high-boiling organic solvent, which has a boiling point higher than that of water (acid aqueous solution). Examples of the organic solvent include cis-decahydronaphthalene, trans-decahydronaphthalene, a mixture of cis- and trans-decahydronaphthalene, 1,2,3,4-tetrahydronaphthalene, long-chain alkanoic acids having carbon atoms of C6 to C18, liquid paraffin, and phthalate esters.

[0042] (Ratio of aqueous acid solution to organic solvent) The ratio of the acid aqueous solution containing the inorganic material and chitosan to the organic solvent is preferably in the range of 0.004:1 to 1:1, more preferably 0.02:1 to 0.25:1. When the ratio of the acid aqueous solution containing the inorganic material and chitosan to the organic solvent is within this range, droplets can be efficiently formed in the dispersion liquid, improving the recovery rate of the abrasive particles. Note that a lower ratio of the acid aqueous solution to the organic solvent tends to decrease the recovery rate of the abrasive particles, while a higher ratio of the acid aqueous solution to the organic solvent tends to make it more difficult to form a sea (organic solvent domain)-island (acid aqueous solution domain containing the inorganic material and chitosan) structure.

[0043] (Stirring speed of dispersion liquid) The formation of droplets from an acid aqueous solution containing an inorganic material and chitosan can be achieved by stirring the dispersion with a stirring blade, for example, ultrasonic stirring, or a rotation-revolution stirrer, but other methods capable of producing droplets are also possible. For example, when stirring with a stirring blade, the stirring speed is preferably set in the range of 10 rpm to 20,000 rpm, more preferably in the range of 50 rpm to 3,000 rpm. Here, the faster the stirring speed, the finer the droplets (chitosan particles) become, resulting in a smaller particle size of the resulting abrasive particles. The slower the stirring speed, the larger the droplets (chitosan particles) become, resulting in a larger particle size of the resulting abrasive particles. In this way, the particle size of the resulting abrasive particles can be controlled simply by adjusting the stirring speed.

[0044] (Dispersion stirring time) The stirring time of the dispersion can be adjusted depending on the degree of droplet formation. For example, when stirring using a stirring blade, the stirring time is preferably set in the range of 3 to 24 hours, more preferably 6 to 10 hours. Here, the longer the stirring time, the finer the droplets (chitosan particles) become, and the smaller the particle size of the resulting abrasive particles can be. Conversely, the shorter the stirring time, the larger the droplets (chitosan particles) become, and the larger the particle size of the resulting abrasive particles can be. In this way, the particle size of the resulting abrasive particles can be controlled by simply adjusting the stirring time.

[0045] (Heating conditions of dispersion liquid) The temperature at which the dispersion is heated is not particularly limited as long as it can evaporate water from droplets of the acid aqueous solution containing the inorganic material and chitosan, but for example, at atmospheric pressure, a temperature in the range of 50°C to the boiling point of water is preferred, and a temperature in the range of 60°C to 90°C is more preferred. Furthermore, the pressure at which the dispersion is heated is not limited to atmospheric pressure; for example, the pressure can be reduced; heating can be performed under reduced pressure. By adjusting the heating conditions for the dispersion, water can be effectively evaporated from the droplets, and abrasive particles can be efficiently obtained.

[0046] (Addition of thickener) Appropriate additives may be added to the dispersion and / or aqueous acid solution. Examples of such additives include thickeners that stabilize droplets in the dispersion. Surfactants are suitable as thickeners. Nonionic surfactants are preferred as such surfactants, and examples include surfactants whose lipophilic group is a higher alcohol having a carbon number of C8 to C18 and has an ester or ether type hydroxy group. Specific examples of surfactants include sorbitan fatty acid esters, sucrose fatty acid esters, glycerin fatty acid esters, polyoxyethylene alkylphenyl ethers (RC6H4O(CH2CHO)nH) such as Triton-X, polyoxyalkylene alkyl ethers (RO((CH2)mO)nH), and alkyl glycosides.

[0047] (Amount of thickener added) The amount of thickener added is preferably in the range of 0.01g to 0.30g per 1ml of organic solvent, more preferably 0.02g to 0.20g. Adding a thickener to the organic solvent within this range allows for efficient droplet formation and stabilizes the droplets formed. Adding a small amount of thickener to the organic solvent tends to result in unstable droplets, while adding a large amount of thickener to the organic solvent tends to inhibit phase separation between the acid aqueous solution and the organic solvent, making droplet formation difficult. Furthermore, the more thickener added to the organic solvent, the finer the droplets (chitosan particles) become, resulting in a smaller particle size for the resulting abrasive particles. Adding a smaller amount of thickener to the organic solvent results in larger droplets (chitosan particles), resulting in a larger particle size for the resulting abrasive particles. Thus, the particle size of the resulting abrasive particles can be controlled simply by adjusting the amount of thickener added.

[0048] (Viscosity of dispersion) The viscosity of the dispersion is preferably in the range of 1 mPa·s to 400 mPa·s (when the dispersion is at 25°C). A dispersion viscosity within this range allows for efficient droplet formation and stabilizes the formed droplets. A low viscosity dispersion tends to result in unstable droplets, while a high viscosity dispersion tends to inhibit phase separation between the acid aqueous solution and the organic solvent, making droplet formation difficult. Furthermore, increasing the viscosity of the dispersion results in finer droplets (chitosan particles), resulting in smaller particle sizes for the resulting abrasive particles. A lower viscosity dispersion results in larger droplets (chitosan particles), resulting in larger particle sizes for the resulting abrasive particles. Thus, the particle size of the resulting abrasive particles can be controlled simply by adjusting the viscosity of the dispersion.

[0049] Granulation methods for cellulose, a polysaccharide like chitosan, can be broadly classified by particle formation mechanism into the O / W and W / O methods, which utilize the hydrophobic effect, and the W / W method, which utilizes charge repulsion. Among these, the only method for composite particle formation between inorganic materials and cellulose is the W / W method, which utilizes charge repulsion with inorganic materials and prepares water-soluble cellulose by complexing cellulose with functional groups such as xanthate groups, cuprammonium, or calcium rhodanate. However, complexing functional groups such as xanthate groups, cuprammonium, or calcium rhodanate requires sulfur compounds and ammonia, resulting in a cumbersome process and a strong odor. Furthermore, the resulting cellulose derivatives are unstable, requiring storage techniques and limiting the ability to increase their concentration. Although cellulose has a rigid structure due to hydrogen bonds, it is poorly soluble in water and solvents, does not melt with heat, and is poorly processable. Furthermore, cellulose contains three hydrogen groups, making reaction control difficult.

[0050] (1st dispersion medium) The first dispersion medium of the first polishing liquid is not particularly limited as long as it is a liquid, but it is usually an aqueous medium mainly composed of water, a rust inhibitor such as an alcohol amine, and a water-soluble organic solvent. The first dispersion medium other than water is preferably a water-soluble organic solvent, such as alcohols such as ethanol, normal propanol, and 2-propanol, or a pyrrolidone-based solvent.

[0051] (Additives for the first polishing liquid) An additive may be added to the first polishing liquid. Examples of additives that can be added include polysaccharide fibers such as cellulose nanofibers, chitin nanofibers, chitosan nanofibers, and carboxymethylcellulose nanofibers. The polysaccharide fibers preferably have a positive surface charge in the pH range in which the first polishing liquid is used for polishing. Since many of the objects to be polished, such as SiC, have a negative charge, polysaccharide fibers with a positive apparent surface charge can capture polishing debris generated during polishing by the electrostatic interaction between the polishing debris and the polysaccharide fiber. By capturing polishing debris with the polysaccharide fiber, the smoothness of the polished surface of the object can be improved.

[0052] (Polysaccharide fiber size) The polysaccharide fiber used as an additive is preferably a so-called polysaccharide nanofiber, having at least a nano-sized fiber diameter (minor axis) of 1 nm to 999 nm. The polysaccharide fiber preferably has a fiber diameter in the range of 4 nm to 999 nm and a fiber length (major axis) in the range of 4 nm to 10,000 nm. Thus, it is preferable to use polysaccharide fibers smaller in size than the micro-sized abrasive grains (first abrasive). Polysaccharide fibers of the aforementioned size, which have a lower specific gravity than the first abrasive grains, can form agglomerates of appropriate size with the first abrasive grains, thereby providing excellent anti-settling properties that prevent the abrasive grains from settling. Furthermore, agglomerations of appropriate size can be formed by the agglomeration of the polysaccharide fiber and the first abrasive grains, allowing the object to be polished efficiently with the first polishing liquid. The size of the polysaccharide fiber was measured using a field emission scanning electron microscope (SEM).

[0053] (Polysaccharide fiber concentration in the first polishing solution) In the first polishing liquid, the concentration of polysaccharide nanofibers as an additive is preferably in the range of 0.01 wt% to 5 wt%, more preferably 0.5 wt% to 1 wt%. When the concentration of polysaccharide nanofibers in the first polishing liquid is within this range, settling of the first abrasive, such as abrasive particles, can be suppressed, thereby improving the polishing rate. Furthermore, when the concentration of polysaccharide nanofibers in the first polishing liquid is within this range, excessive viscosity can be suppressed, and the frictional effect between the first abrasive, such as abrasive particles, and the surface plate can be increased, thereby improving the polishing rate. Note that, when the concentration of polysaccharide nanofibers in the first polishing liquid is low, the first abrasive, such as abrasive particles, tends to settle more easily, resulting in a decrease in the polishing rate. Furthermore, when the concentration of polysaccharide nanofibers in the first polishing liquid is high, the viscosity of the first polishing liquid increases, reducing the frictional effect between the first abrasive, such as abrasive particles, and the surface plate, resulting in the first abrasive slipping on the surface plate, which tends to slow down the polishing rate.

[0054] (pH of first polishing solution) The first polishing liquid is set to a pH of 5.8 or higher and is used for polishing in the first polishing step at a pH of 5.8 or higher. The pH of the first polishing liquid is adjusted with a pH adjuster as needed to maintain a pH of 5.8 or higher. The pH of the first polishing liquid is preferably in the range of 5.8 to 13.0, more preferably 5.8 to 10.0, and even more preferably 5.8 to 8.5. Chitosan particles maintain their particle shape in the first polishing liquid at a pH within this range, thereby increasing the apparent size of the abrasive particles and providing other benefits such as elasticity. Chitosan particles tend to dissolve in solvents with a pH lower than 5.8, particularly in solvents with a pH lower than 5.0. Chitosan tends to hydrolyze in strongly alkaline solutions, so increasing the pH of the first polishing liquid too much is thought to result in little improvement in the polishing rate.

[0055] The abrasive particles contain inorganic materials with a negative surface charge in the neutral pH range, and polysaccharide fibers with a positive surface charge in the neutral pH range. The abrasive particles and polysaccharide fibers aggregate to form aggregates in a first polishing solution with a pH of 5.8 or higher. This allows for an improved polishing rate and improved anti-settling effect due to the aggregates having a larger apparent size than the abrasive particles. The chitosan particles and polysaccharide fibers that make up the abrasive particles tend to dissolve in the first polishing solution when the pH of the first polishing solution is lower than 5.8, making it difficult for the abrasive particles and polysaccharide fibers to aggregate. For example, in the case of chitosan fiber, chitosan is not water-soluble under neutral or alkaline conditions, but becomes water-soluble under weakly acidic conditions due to the protonation of its amino groups (see Figure 2). In other words, it is desirable to use polysaccharide fibers that are insoluble or hardly soluble in the first polishing liquid at a pH of 5.8 or higher. For example, chitosan fibers that are hardly soluble or insoluble in this pH range have the advantage that the addition of polysaccharide fibers does not increase the viscosity of the first polishing liquid. Here, as the pH of the first polishing liquid becomes more alkaline, the surface charge (zeta potential) of the polysaccharide fibers becomes more negative, and the ability of the polysaccharide fibers to collect polishing debris tends to weaken.

[0056] (pH adjuster) Examples of pH adjusters for adjusting the pH of the first polishing solution include hydrochloric acid, nitric acid, acetic acid, lactic acid, formic acid, acrylic acid, methacrylic acid, propionic acid, butyric acid, glacial acetic acid, resorcinol, aromatic sulfonic acids such as phenol and benzenesulfonic acid, aromatic carboxylic acids such as catechins and benzoic acid, alkylphenols such as o-cresol, m-cresol, p-cresol, and xylenol, and organic acids such as ascorbic acid. Organic acids are preferred for protecting the surface plate. Furthermore, alkali metal or alkaline earth metal bases can be used as pH adjusters. Monovalent acids are particularly preferred because they prevent chitosan crosslinking in the first polishing solution, making it easier to dissolve chitosan particles in the second polishing solution.

[0057] (Abrasive content in first polishing liquid) The first abrasive is preferably contained in the first dispersion medium in a range of 0.02 wt % to 5.0 wt %. By containing the first abrasive in the above range, the object to be polished can be efficiently polished by the first polishing liquid.

[0058] (Second polishing liquid) The second polishing liquid used in the second polishing step has a pH range in which the chitosan particles cannot maintain their particle shape (the chitosan particles dissolve). The second polishing liquid also contains a second polishing material. In the second polishing liquid, the second polishing material is dispersed in a second dispersion medium. Examples of the second abrasive include single crystal diamond, polycrystalline diamond, silicon carbide, silica, anatase titanium dioxide, rutile titanium dioxide, boron carbide, aluminum (III) oxide, zirconia, iron (II) oxide (FeO), triiron tetroxide (magnetite, Fe3O4), α-iron (III) oxide, β-iron (III) oxide, γ-iron (III) oxide, ε-iron (III) oxide, α-iron oxyhydroxide, β-iron oxyhydroxide, γ-iron oxyhydroxide, δ-iron oxyhydroxide, limonite, ferrihydrite, schwertmannite, graphite, chromium oxide, ceria (cerium oxide), gallium nitride, boron nitride, zinc oxide, tin oxide, manganese oxide, barium carbonate, calcium carbonate, magnesium carbonate, garnet, and clay minerals such as montmorillonite, bentonite, sericite, and mica. Examples of the second abrasive include those used in polishing, and these may be used alone or in combination. The second abrasive is preferably a photocatalytic inorganic material that exhibits catalytic action when irradiated with light, such as titanium oxide, ceria (cerium oxide), zirconium oxide, and zinc oxide.

[0059] (Second abrasive material) The second abrasive is selected appropriately according to the object to be polished, and preferably has a negative surface charge in an aqueous solvent having a pH of 10 or less. Examples of second abrasives that have a negative surface charge in an aqueous solvent having a pH of 10 or less include titanium dioxide, zirconia, ceria (cerium oxide), and zinc oxide.

[0060] (Average particle size of second abrasive) The average particle size of the second abrasive is preferably smaller than that of the first abrasive, such as abrasive particles. The average particle size of the second abrasive can be selected depending on the function required of the second polishing liquid, but is preferably in the range of 5 nm to 10 μm, and more preferably in the range of 200 nm to 1 μm. When the average particle size of the second abrasive is within the above range, the object to be polished can be polished efficiently and precisely. Note that if the particle size of the second abrasive is reduced to the molecular level, it becomes difficult for the second abrasive to perform its function, and if the particle size is increased, it becomes more likely to settle during polishing.

[0061] (Second dispersion medium) The second dispersion medium of the second polishing liquid is not particularly limited as long as it is a liquid, but it is usually an aqueous medium mainly composed of water, a rust inhibitor such as an alcohol amine, and a water-soluble organic solvent. The second dispersion medium other than water is preferably a water-soluble organic solvent, such as alcohols such as ethanol, normal propanol, and 2-propanol, or a pyrrolidone-based solvent.

[0062] (Additives for the second polishing liquid) An additive may be added to the second polishing liquid. Examples of additives that can be added include polysaccharide fibers such as cellulose nanofibers, chitin nanofibers, chitosan nanofibers, and carboxymethylcellulose nanofibers. The polysaccharide fibers preferably have a positive surface charge in the pH range in which the second polishing liquid is used for polishing. Since many of the objects to be polished, such as SiC, have a negative charge, polysaccharide fibers with a positive apparent surface charge can capture polishing debris generated during polishing by the electrostatic interaction between the polishing debris and the polysaccharide fiber. By capturing polishing debris with the polysaccharide fiber, the smoothness of the polished surface of the object can be improved.

[0063] (Polysaccharide fiber size) The polysaccharide fiber used as an additive is preferably a so-called polysaccharide nanofiber, having at least a nano-sized fiber diameter (minor axis) (1 nm to 999 nm). The polysaccharide fiber preferably has a fiber diameter in the range of 4 nm to 999 nm and a fiber length (major axis) in the range of 4 nm to 10,000 nm. Thus, it is preferable to use polysaccharide fibers smaller in size than micro-sized abrasive grains (abrasives). Polysaccharide fibers of the aforementioned size, which have a lower specific gravity than the second abrasive, can form agglomerates of appropriate size with the second abrasive, thereby providing good anti-settling properties that prevent the second abrasive from settling. Furthermore, agglomerations of appropriate size are formed by the agglomeration of the polysaccharide fiber and the second abrasive, allowing the object to be polished efficiently with the second polishing liquid. The size of the polysaccharide fiber was measured using a field emission scanning electron microscope (SEM).

[0064] (Polysaccharide fiber concentration in the second polishing solution) In the second polishing liquid, the concentration of the polysaccharide nanofiber as an additive is preferably in the range of 0.01 wt% to 5 wt%, more preferably in the range of 0.5 wt% to 1 wt%. When the concentration of the polysaccharide nanofiber in the second polishing liquid is within this range, sedimentation of the second abrasive can be suppressed, thereby improving the polishing rate. Furthermore, when the concentration of the polysaccharide nanofiber in the second polishing liquid is within this range, excessive viscosity can be suppressed, and the frictional effect between the second abrasive and the platen can be increased, thereby improving the polishing rate. Note that, as the concentration of the polysaccharide nanofiber in the second polishing liquid decreases, the second abrasive tends to settle more easily, resulting in a decrease in the polishing rate. Furthermore, as the concentration of the polysaccharide fiber in the second polishing liquid increases, the viscosity of the second polishing liquid increases, reducing the frictional effect between the second abrasive and the platen, resulting in the second abrasive slipping on the platen, which tends to prevent an increase in the polishing rate.

[0065] (pH of second polishing liquid) The second polishing liquid is set to a pH of 5.0 or less and is used for polishing in the second polishing step at a pH of 5.0 or less. The pH of the second polishing liquid is adjusted with a pH adjuster as needed to maintain a pH of 5.0 or less. The pH of the second polishing liquid is preferably in the range of 1.0 to 5.0, and even more preferably in the range of 2.0 to 3.0. Chitosan particles constituting the abrasive particles tend to dissolve in liquids with a pH lower than 5.8. This is thought to be due to the fact that chitosan becomes water-soluble under weakly acidic conditions due to protonation of its amino group (see FIG. 2). Thus, by supplying a second polishing liquid with a pH of 5.0 or less to a platen containing abrasive particles based on chitosan particles, the chitosan particles can be dissolved and the abrasive particles can be removed from the platen.

[0066] (pH adjuster) Examples of pH adjusters for adjusting the pH of the second polishing liquid include hydrochloric acid, nitric acid, acetic acid, lactic acid, formic acid, acrylic acid, methacrylic acid, propionic acid, butyric acid, glacial acetic acid, resorcinol, phenol, aromatic sulfonic acids such as benzenesulfonic acid, aromatic carboxylic acids such as catechins and benzoic acid, alkylphenols such as o-cresol, m-cresol, p-cresol, and xylenol, and organic acids such as ascorbic acid. From the viewpoint of protecting the surface plate, organic acids are preferred. Furthermore, alkali metal or alkaline earth metal bases can be used as pH adjusters.

[0067] (Abrasive content in second polishing liquid) The second abrasive is preferably contained in the second dispersion medium in an amount of 0.1 wt% to 20.0 wt%, more preferably 5.0 wt% to 6.0 wt%. By containing the second abrasive in the above range, the object to be polished can be efficiently polished by the second polishing liquid.

[0068] The second polishing liquid can be obtained by mixing a second abrasive, an additive, etc., as needed, with a second dispersion medium.

[0069] The second abrasive preferably has an isoelectric point or point of zero charge higher than 5. Examples of second abrasives with an isoelectric point or point of zero charge higher than 5 include aluminum oxide, chromium oxide, magnesium oxide, triiron tetroxide (magnetite, Fe2O4), α-iron(III) oxide, γ-iron(III) oxide, α-iron oxyhydroxide, β-iron oxyhydroxide, γ-iron oxyhydroxide, ferrihydrite, limonite, schwertmannite, calcium carbonate, barium carbonate, titanium dioxide (rutile, anatase), ceria (cerium oxide), and zinc oxide. If the isoelectric point or point of zero charge is 5 or higher, agglomeration is unlikely to occur when used as abrasive grains in a second polishing liquid with a pH of 5.0 or less, and the abrasive grains in the second polishing liquid are more likely to be uniformly dispersed on the surface plate. As a result, the surface roughness of the resulting polished product can be reduced. Furthermore, the polysaccharide nanofibers added to the first polishing liquid and the second polishing liquid may be the same or different in fiber type, length, or type.

[0070] (1st polishing process) A first polishing liquid is supplied to a surface plate. The object to be polished is pressed against the surface plate while the object and the surface plate are rotated relative to each other, thereby polishing the object with the surface plate and smoothing the surface of the object to be polished. The first polishing liquid is supplied continuously or intermittently. The first polishing liquid may be dripped either upstream or downstream of the object to be polished.

[0071] (Amount of first polishing liquid supplied) The polishing conditions using the first polishing liquid according to the present disclosure are appropriately set depending on the object to be polished, the purpose of polishing, and the like, and can be, for example, as follows: The amount of the first polishing liquid supplied to the platen per unit time is preferably in the range of 0.1 ml / min to 10 ml / min. By setting the supply amount of the first polishing liquid within this range, the polishing rate can be improved. Note that if the supply amount is too small, the polishing rate does not increase, and if the supply amount is too large, the object to be polished tends to slide, preventing the polishing rate from increasing. The supply amount of the first polishing liquid per unit time may be constant in the first polishing step, may be increased stepwise or linearly in the first polishing step, or may be decreased stepwise or linearly in the first polishing step.

[0072] (Surface pressure in the first polishing process) The surface pressure of the object to be polished pressed against the platen in the first polishing step is 50 gf / cm 2 ~300gf / cm 2 is preferred, and more preferably 120 gf / cm 2 ~250gf / cm 2 When the surface pressure is within the above range, the polishing rate can be improved while suppressing scratches. Note that the lower the surface pressure, the slower the polishing rate, and the higher the surface pressure, the more likely scratches tend to occur. The surface pressure in the first polishing step may be constant, increased stepwise or linearly, or decreased stepwise or linearly in the first polishing step.

[0073] (Rotation speed of the surface plate in the first polishing process) The rotation speed of the platen in the first polishing step is preferably in the range of 10 rpm to 120 rpm, more preferably in the range of 30 rpm to 80 rpm. When the rotation speed is within this range, the polishing rate can be improved while suppressing scratches. Note that the slower the rotation speed, the less the polishing rate increases, while the faster the rotation speed, the more likely scratches are to occur. The rotation speed in the first polishing step may be constant, increased stepwise or linearly, or decreased stepwise or linearly in the first polishing step.

[0074] (Action and effect of the first polishing liquid) According to the first abrasive and first polishing liquid of the present disclosure, abrasive grains are supported on chitosan particles through electrostatic interaction, allowing abrasive grains with a larger apparent particle size than the abrasive grains to act on the object to be polished, thereby improving the polishing rate. It is known that the polishing rate of objects such as SiC increases with increasing abrasive grain size. However, simply increasing the abrasive grain size can lead to various problems, such as an increase in the thickness of the damaged layer (process-affected layer) and significant processing marks remaining on the object to be polished, resulting in a deterioration in smoothness. Furthermore, in the process following lapping, the process-affected layer is removed by etching or polishing. However, etching SiC and other materials requires the use of hazardous molten potassium hydroxide (KOH), making it industrially difficult from an equipment and operational standpoint. Therefore, polishing is only possible with small abrasive grains, and the size of the diamond grains used as abrasive grains in this process generally corresponds to the size of the first abrasive (abrasive grains) according to the present disclosure. The abrasive particles of the present disclosure have a soft core composed of chitosan particles, which reduces the surface roughness of the polishing surface of the object to be polished, and the unique relaxation effect of chitosan reduces scratches on the polishing surface. Furthermore, the abrasive particles, whose apparent size is larger than the abrasive grain size, improve the polishing rate, thereby reducing the thickness of the process-affected layer. Thus, the abrasive particles of the present disclosure and the first polishing liquid containing these abrasive grains can improve the polishing rate without increasing the size of the abrasive grains themselves. Since the abrasive grains themselves are not large, the thickness of the process-affected layer can be reduced, improving the smoothness of the object to be polished.

[0075] The abrasive particles according to the present disclosure have a lower apparent density than abrasive grains, making them less likely to settle in the first polishing liquid. Because the first polishing liquid thus prevents abrasive grains from settling in the supply path of the first polishing liquid in a polishing apparatus, the abrasive grains can be efficiently delivered to the workpiece to be polished. Therefore, the first polishing liquid according to the present disclosure can reduce the amount of abrasive grains required for polishing, which can contribute to reducing the cost of polishing hard materials such as SiC and GaN, which require expensive abrasive grains such as diamond. Furthermore, the first polishing liquid does not prevent abrasive grains from settling by increasing the viscosity with a dispersant or additive, but instead uses abrasive grains composed of chitosan particles carrying abrasive grains. This allows the viscosity of the first polishing liquid to be kept low, even to the same level as pure water. A low-viscosity first polishing liquid can increase the coefficient of kinetic friction during polishing, thereby improving the polishing rate. Furthermore, the first polishing liquid has a low viscosity, which reduces the flow resistance in the supply path of the first polishing liquid in the polishing apparatus, and can be efficiently supplied to the object to be polished.

[0076] (Second polishing process) A second polishing liquid is supplied to the surface plate. The supply of the second polishing liquid may be started after the supply of the first polishing liquid is stopped, or the supply of the second polishing liquid may be started while the first polishing liquid is being supplied and then stopped. When the supply of the second polishing liquid is started, the first polishing material containing abrasive particles remains on the surface plate, and the first polishing material and the second polishing material are mixed together in the initial stage of the second polishing process. From the viewpoint of improving the polishing rate, it is preferable to start the supply of the second polishing liquid after stopping the supply of the first polishing liquid. Then, the object to be polished is pressed against the surface plate and the surface plate are rotated relative to each other, thereby polishing the object to a mirror finish. The second polishing liquid is supplied continuously or intermittently. The second polishing liquid may be dripped either upstream or downstream of the object to be polished.

[0077] When the second polishing liquid contains a photocatalytic inorganic material as the second abrasive, it is preferable to irradiate the second polishing liquid supplied to the surface plate with light to activate the photocatalytic action of the photocatalytic inorganic material. In this way, the photocatalytic action of the photocatalytic inorganic material allows efficient chemical polishing of the object to be polished, thereby improving the polishing rate. Here, the light irradiated onto the photocatalytic inorganic material is preferably ultraviolet light. Among ultraviolet light, it is preferable that the wavelength is in the range of 200 nm to 400 nm. A wavelength in the range of 200 nm to 400 nm is preferable because it can efficiently induce the photocatalytic activity of the photocatalytic inorganic material. Furthermore, the irradiation intensity of the light is 5 mW / cm. 2 ~5000mW / cm 2 , preferably 200 mW / cm 2 ~3500mW / cm 2 It is preferable to irradiate the surface plate from a distance of 2 cm to 30 cm within this range. When the light irradiation intensity is within this range, catalytic action is sufficiently induced, and deterioration of the surface plate due to the ultraviolet light and heat from the light source and evaporation of the second polishing liquid can be suppressed. The illuminance and irradiation intensity of the light may be constant during the second polishing step, or may be increased stepwise or linearly during the second polishing step, or may be decreased stepwise or linearly during the second polishing step. Furthermore, light irradiation may be continuous or intermittent. The light irradiation position may be either upstream or downstream of the dripping position of the second polishing liquid, but in order to efficiently induce photocatalytic action, it is preferable to irradiate the light downstream of the dripping position of the second polishing liquid.

[0078] (Amount of second polishing liquid supplied) The polishing conditions using the second polishing liquid according to the present disclosure are appropriately set depending on the object to be polished, the purpose of polishing, and the like, but can be, for example, as follows: The amount of the second polishing liquid supplied to the platen per unit time is preferably in the range of 0.1 ml / min to 10 ml / min. By setting the supply amount of the second polishing liquid within the above range, the polishing rate can be improved. Note that if the supply amount is too small, the polishing rate does not increase, and if the supply amount is too large, the object to be polished tends to slide, preventing the polishing rate from increasing. The supply amount of the second polishing liquid per unit time may be constant in the second polishing step, may increase stepwise or linearly in the second polishing step, or may decrease stepwise or linearly in the second polishing step. Here, the supply amount of the second polishing liquid per unit time is preferably greater than the supply amount of the first polishing liquid per unit time.

[0079] (Surface pressure in the second polishing process) The surface pressure of the object to be polished pressed against the platen in the second polishing process is 50 gf / cm 2 ~300gf / cm 2 is preferred, and more preferably 120 gf / cm 2 ~250gf / cm 2 The surface pressure is in the range. When the surface pressure is in the above range, the polishing rate can be improved while suppressing scratches. Note that the lower the surface pressure, the less the polishing rate increases, and the higher the surface pressure, the more likely scratches tend to occur. The surface pressure in the second polishing step may be constant, may be increased stepwise or linearly, or may be decreased stepwise or linearly in the second polishing step. Here, it is preferable that the surface pressure in the second polishing step is lower than the surface pressure in the first polishing step.

[0080] (Rotation speed of the surface plate in the second polishing process) The rotation speed of the platen in the second polishing step is preferably in the range of 10 rpm to 120 rpm, more preferably in the range of 30 rpm to 80 rpm. A rotation speed within this range can improve the polishing rate while suppressing scratches. Note that the slower the rotation speed, the less the polishing rate increases, while the faster the rotation speed, the more likely scratches tend to occur. The rotation speed in the second polishing step may be constant, or may be increased stepwise or linearly, or may be decreased stepwise or linearly, in the second polishing step. Preferably, the rotation speed in the second polishing step is slower than the rotation speed in the first polishing step.

[0081] (Surface plate) The polishing platen (pad) used can be made of, for example, a plastic, cast iron, stainless steel, ceramic, quartz, or granite polishing plate, with a plastic polishing plate being the most preferred. The shape of the platen is not particularly limited, but any shape capable of holding an abrasive, such as a honeycomb shape, is sufficient. For plastic platens, the Shore A hardness is preferably in the range of 0 to 100, with a Vickers hardness (HV) of 2.5 to 40 being preferred. For inorganic material platens, the Vickers hardness (HV) is preferably in the range of 4 to 2000. For platens made of a composite material of plastic and inorganic material, the Shore A hardness is preferably in the range of 0 to 100, with a Vickers hardness (HV) of 2.5 to 2000 being preferred.

[0082] The same surface plate can be used for polishing with the first polishing liquid and polishing with the second polishing liquid. That is, the surface plate used in the first polishing step can be used in the second polishing step without changing it, with the first polishing liquid still remaining on the surface plate. Also, a relatively soft surface plate for polishing can be used in the first polishing step.

[0083] (auxiliary agent) In both or one of the first and second polishing steps, an auxiliary agent may be supplied to the surface plate. Examples of the auxiliary agent include rust inhibitors such as lactic acid, surfactants, pH adjusters, etching agents, complexing agents, oxidizing agents, and preservatives. Examples of the preservative include ascorbic acid, sodium benzoate, and isopropylmethylphenol. The amount of the auxiliary agent supplied to the surface plate per unit time is preferably in the range of 0.1 ml / min to 1.5 ml / min.

[0084] (Action and effect of the second polishing liquid) When the second polishing liquid is supplied to the platen, the pH of the second polishing liquid is below 5.0, so the chitosan particles in the abrasive particles present on the platen dissolve and gradually become smaller. The chitosan particles completely dissolve and are discharged from the platen along with the second polishing liquid overflowing from the platen. Furthermore, the inorganic material supported by the chitosan particles settles and is discharged from the platen along with the second polishing liquid overflowing from the platen. The abrasive particles present on the platen are replaced by the second abrasive from the first polishing liquid, replacing the first abrasive from the first polishing liquid. In this way, the abrasive particles based on chitosan particles can be dissolved and discharged with the second polishing liquid. Therefore, the platen used in the first polishing step can be used in the second polishing step without removing the first polishing liquid. In this way, the transition from the first polishing step to the second polishing step eliminates the need for the usual tasks involved in transitioning from lapping to polishing, such as changing the polishing equipment, transferring the workpiece to be polished, replacing the platen, and removing the first polishing liquid from the platen. Therefore, the time and labor required to perform processes from lapping to polishing on an object to obtain a polished product can be significantly reduced, and the polishing speed of the object can be improved.

[0085] The method for manufacturing a polished product according to the present disclosure includes a coexistence period during which the abrasive particles and the second abrasive coexist. During this coexistence period, the chitosan particles in the abrasive particles gradually dissolve and are discharged, causing the relatively large abrasive particles to gradually become smaller and be replaced by the second abrasive, which is smaller than the abrasive particles. In this way, rather than a sudden change from large to small abrasive particles, the abrasive particles contributing to the polishing of the object to be polished gradually become smaller. In the initial stage of the second polishing step, the polishing speed can be gradually reduced, thereby improving the polishing rate. As the second polishing step progresses, the abrasive particles are discharged, preventing scratches caused by the abrasive particles and enabling the object to be polished more precisely.

[0086] (Application) The method for manufacturing a polished workpiece according to the present disclosure can be used to polish metal materials such as cast iron, alloy steel, copper, copper alloy, aluminum, aluminum alloy, and cemented carbide, as well as brittle materials such as SiC (silicon carbide), GaN (gallium nitride), GaO (gallium oxide), silicon wafers, ceramics, quartz, and glass. The polishing method according to the present disclosure can also be used in surface grinding, cylindrical grinding, internal grinding, honing, centerless grinding, slicing, lapping, polishing, and other processes. Among these, the method is particularly suitable for polishing hard materials such as SiC (silicon carbide) because it can improve the polishing rate.

[0087] Next, the method for manufacturing a ground product according to the present invention will be described below by way of examples with reference to the accompanying drawings. [Example]

[0088] (Abrasive particles of the first abrasive) The abrasive particles used as the first abrasive in the first polishing liquids of Examples 1 to 56 and Comparative Examples 1 to 6 were prepared as follows. Chitosan was dissolved in a solution of lactic acid (same amount as chitosan's amino group equivalent) in pure water to prepare a chitosan-acid aqueous solution containing 7.5 wt% chitosan. 10 g (400 wt% of chitosan) of single crystal diamond (manufactured by Dia Material Co., Ltd., average particle size 9 μm) was added to 33.3 g of the chitosan-acid aqueous solution to prepare an inorganic material-chitosan-acid aqueous solution. The inorganic material-chitosan-acid aqueous solution had a pH of 5.3, and the zeta potential of the single crystal diamond in the acid aqueous solution was -50 mV, while the zeta potential of the chitosan in the acid aqueous solution was +65 mV. The inorganic material-chitosan-acid aqueous solution was dispersed by stirring with a magnetic stirrer for 1 hour. Separately, a decalin dispersion was prepared by adding 20 g of a surfactant (polyoxyethylene octylphenyl ether, Dow Chemical, product name: Triton-X) to 500 ml of decalin as an organic solvent, containing 0.04 g / ml of surfactant relative to the decalin. The viscosity of the decalin dispersion was 1.42 mPa·s (decalin dispersion at 25°C). The inorganic material-chitosan-acid aqueous solution was added to the decalin dispersion, and the dispersion was maintained at 85°C. The dispersion was stirred at 375 rpm using a magnetic stirrer for 5 hours, allowing water to evaporate from the inorganic material-chitosan-acid aqueous solution droplets that formed in the dispersion. The resulting abrasive particles were collected by filtration and washed with ethanol. They were then wet-classified using alcohol (Japan Alcohol Sales Co., Ltd., product name: Solmix) through 25 μm and 105 μm sieves, and the diamond-loaded chitosan particles were collected. The recovery rate of the abrasive particles was nearly 100 wt% based on the chitosan and single crystal diamond used.

[0089] The abrasive particles are chitosan particles in which the chitosan has not been crosslinked (uncrosslinked). The particle size of the abrasive particles is as shown in the table. As shown in Figure 5, it can be seen that single crystal diamonds are attached to the surface of the chitosan particles in the abrasive particles.

[0090] (Preparation of first polishing liquid) In Example 1, 12 g of abrasive particles, 100 g of an additive (chitosan nanofiber, Sugino Machine Co., Ltd., product name BiNFi-s chitosa, 2 wt% slurry), and 288 g of water were mixed to prepare a first polishing liquid containing 3 wt% abrasive particles and 0.5 wt% chitosan nanofiber. The first polishing liquids of Examples 2 to 56 were similar to Example 1, with the concentrations of abrasive particles and chitosan nanofiber as an additive being as shown in the table. Lactic acid was added dropwise while stirring the first polishing liquid, and the pH of the first polishing liquid was adjusted to the value shown in the table. In the first polishing liquids of Examples 1 to 56 and Comparative Examples 1 to 6, the first abrasive consisted solely of abrasive particles.

[0091] (Preparation of second polishing liquid) The second polishing solution for Example 1 was prepared as follows. 50 g of a second abrasive (ceria, Showa Denko K.K., trade name: Shorox), 250 g of an additive (chitosan nanofiber, Sugino Machine Corp., trade name: BiNFi-s chitosa, 2 wt% slurry), and 700 g of water were mixed to prepare a second polishing solution containing 5 wt% ceria as the second abrasive and 0.5 wt% chitosan nanofiber. The second polishing solutions for Examples 2 to 56 were similar to those for Example 1, with the concentrations of the second abrasive and chitosan nanofiber as an additive being as shown in the table. While stirring the second polishing solution, lactic acid was added dropwise to adjust the pH of the second polishing solution to the value shown in the table.

[0092] (Abrasive processing equipment) As shown in FIGS. 6 and 7 , the polished workpiece manufacturing apparatus 10 of the embodiment includes a balance plate 14 that supports a surface plate 12 on its upper surface and rotates horizontally, and a polishing head 16 that supports a polished object 50 on its lower surface and rotates horizontally while pressing the polished object 50 against the surface plate 12 supported on the upper surface of the balance plate 14. The balance plate 14 is disk-shaped and rotates horizontally around an axis passing vertically through its center by a driving means such as a motor. The surface plate 12 is detachably attached to the upper surface of the balance plate 14 and rotates horizontally in conjunction with the horizontal rotation of the balance plate 14. The polishing head 16 is disk-shaped and rotates horizontally around an axis passing vertically through its center by a driving means such as a motor. The polished object 50 (the obtained polished workpiece) is detachably attached to the lower surface of the polishing head 16 and rotates horizontally in conjunction with the horizontal rotation of the polishing head 16. The polishing head 16 has a detachable weight, and by changing the weight of the weight, the surface pressure that presses the object 50 to be polished against the surface plate 12 can be adjusted.

[0093] 6 and 7, the manufacturing apparatus 10 includes a first supplying means 18 that supplies a first polishing liquid containing chitosan particles carrying an inorganic material and adjusted to a pH of 5.8 or higher to the platen 12, a second supplying means 20 that supplies a second polishing liquid adjusted to a pH of 5.0 or lower to the platen 12, and a control means 22 that controls the first supplying means 18 and the second supplying means 20. The control means 22 controls the second supplying means 20 to start supplying the second polishing liquid to the platen 12 containing the chitosan particles. The first supplying means 18 includes a first tank 18a that stores the first polishing liquid and a first pump 18b that delivers the first polishing liquid from the first tank 18a to the platen 12 via a pipe. The second supplying means 20 includes a second tank 20a that stores the second polishing liquid and a second pump 20b that delivers the second polishing liquid from the second tank 20a to the platen 12 via a pipe. The first supply means 18 and the second supply means 20 have supply paths independent of each other, and the supply ports to the surface plate 12 are located in the vicinity of the polishing head 16 .

[0094] 6 and 7, the manufacturing apparatus 10 includes an ultraviolet irradiation means 24 that irradiates ultraviolet light toward the surface plate 12. The ultraviolet irradiation means 24 is disposed above the balance plate 14 and spaced apart from the surface plate 12.

[0095] 6 and 7, the manufacturing apparatus 10 of the embodiment includes a third supply means 26 that supplies an auxiliary agent to the surface plate 12. The third supply means 26 includes a third tank 26a that stores the auxiliary agent, and a third pump 26b that sends the auxiliary agent from the third tank 26a toward the surface plate 12 via a pipe.

[0096] (Manufacturing of polished products) A test was conducted to produce a polished product using a wafer as the object to be polished. The polishing conditions for the examples and comparative examples are as shown in the table. The wafers and equipment used in the examples and comparative examples are as follows. Wafer: SiC (silicon carbide) Polishing machine: Musashino Electronics Co., Ltd., Product name: MA-300 Ultraviolet irradiation device: Matsuo Sangyo Co., Ltd., Product name: MS-H1000AF Surface plate: Polypropylene pad, hardness Shore D70

[0097] (1st polishing process) Before polishing, the first polishing solution was dropped onto the platen at the supply rate shown in the table while the platen was rotated to allow the first polishing solution to settle into the platen. The wafer was then placed on the platen, and a weight was placed on top to achieve the specified weight, and the first polishing step began. Furthermore, a lactic acid solution (2 wt% lactic acid dispersed in distilled water) was supplied to the platen as an auxiliary agent at the supply rate shown in the table during the first polishing step. The polishing conditions for the first polishing step, such as the supply rate of the first polishing solution per unit time, the rotation speed of the platen, and the surface pressure of the wafer pressed against the platen, were as shown in the table. The first polishing step was carried out for 4 hours.

[0098] (Second polishing process) After the first polishing step was performed for four hours, the supply of the first polishing solution was stopped and the rotation of the platen was stopped. The weight of the weight was then adjusted, and the second polishing step was initiated by starting the dripping of the second polishing solution and rotating the platen. At the start of the second polishing step, the second polishing step was performed while irradiating the platen with ultraviolet light of the wavelength and intensity shown in the table from a position 3 cm away from the platen using an ultraviolet irradiation device. A lactic acid solution (2 wt% lactic acid dispersed in distilled water) was supplied to the platen as an auxiliary agent at the supply rate shown in the table. The polishing conditions for the second polishing step, such as the supply rate of the second polishing solution per unit time, the rotation speed of the platen, and the surface pressure of the wafer pressed against the platen, were as shown in the table. The second polishing step was performed for five hours.

[0099] After the second polishing step was performed for 5 hours, the wafer was removed from the apparatus, washed with distilled water, and dried by air blowing. After the wafer was dried, the weight of the wafer was measured, and the polishing rate was calculated, and then the surface roughness was measured. In both the examples and comparative examples, the first polishing step was performed for 4 hours, and the second polishing step was performed for 5 hours.

[0100] The polishing rate was calculated from the difference in weight before and after polishing and the polishing time. Specifically, the wafer before polishing was thoroughly washed and dried, and the weight (W1) was measured. After the polishing operation, the wafer was thoroughly washed and dried, and the weight (W2) was measured. The difference in weight before and after polishing was used as the specific gravity of the wafer (3.21 g / cm 3 The total removal rate (R) was calculated by dividing the total removal rate (R) by the total removal time (T (9 hours)) of the wafer. Total polishing rate (R) = (W1-W2) / (3.21 x A x T) The surface roughness was measured using a stylus surface profiler (ULVAC, product name Dektak150) and the arithmetic mean roughness (Ra) was calculated from one-dimensional measurements with a measurement width of 10 μm.

[0101] The results of the polishing tests are shown in Tables 1 to 7.

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] [Table 4]

[0106] [Table 5]

[0107] [Table 6]

[0108] [Table 7]

[0109] (Comparative ratio) For comparison, the polishing rate, surface roughness, and total polishing time are shown for the four steps of primary mechanical polishing, secondary mechanical polishing, primary chemical mechanical polishing, and secondary chemical mechanical polishing. The primary mechanical polishing was performed using a cast iron surface plate, the secondary mechanical polishing using a tin surface plate, the primary chemical mechanical polishing using a hard plastic pad, and the secondary chemical mechanical polishing using a soft plastic pad. The polishing solutions used in the primary mechanical polishing, secondary mechanical polishing, primary chemical mechanical polishing, and secondary chemical mechanical polishing are as follows. For comparison, polishing was performed using the same polishing apparatus as in the examples and comparative examples, and the polishing conditions were as follows:

[0110] The polishing solution for the comparative primary mechanical polishing was prepared by dispersing single crystal diamond (manufactured by Diamond Material Co., Ltd., average particle size 9 μm) as abrasive grains in distilled water. The pH of the polishing solution for the primary mechanical polishing was 7. The primary mechanical polishing for the comparative example was carried out with a supply rate of the polishing solution of 1.4 mL / min, a rotation speed of the surface plate of 75 rpm, and a surface pressure of 240 gf / cm. 2 In addition, distilled water was supplied to the platen as an auxiliary agent at a rate of 0.2 mL / min. The polishing time for the primary mechanical polishing, which is a comparative example, is 3 hours.

[0111] The polishing solution for the secondary mechanical polishing in comparison was prepared by dispersing single crystal diamond (manufactured by Diamond Material Co., Ltd., average particle size 3 μm) as abrasive grains in distilled water. The pH of the polishing solution for the secondary mechanical polishing was 7. The secondary mechanical polishing in comparison was carried out with a supply rate of the polishing solution of 1.4 mL / min, a rotation speed of the surface plate of 75 rpm, and a surface pressure of 240 gf / cm. 2 In addition, distilled water was supplied to the platen as an auxiliary agent at a rate of 0.2 mL / min. The polishing time for the secondary mechanical polishing, which is a comparative example, is 4 hours.

[0112] The polishing solution for the primary chemical mechanical polishing in comparison was prepared by dispersing single crystal diamond (manufactured by Diamond Material Co., Ltd., average particle size 0.5 μm) as abrasive grains in distilled water. The pH of the polishing solution for the primary chemical mechanical polishing was 7. The primary chemical mechanical polishing in comparison was carried out with a supply rate of the polishing solution of 2.0 mL / min, a rotation speed of the surface plate of 75 rpm, and a surface pressure of 66.6 gf / cm. 2 In addition, distilled water was supplied to the platen as an auxiliary agent at a rate of 0.2 mL / min. The polishing time for the primary chemical mechanical polishing, which is a comparative example, was 4 hours.

[0113] The polishing solution for the comparative secondary chemical mechanical polishing was prepared by dispersing single crystal diamond (manufactured by Diamond Material Co., Ltd., average particle size 0.2 μm) as abrasive grains in distilled water. The pH of the polishing solution for the comparative secondary chemical mechanical polishing was 7. The supply rate of the polishing solution for the comparative secondary chemical mechanical polishing was 2.0 mL / min, the rotation speed of the platen was 75 rpm, and the surface pressure was 66.6 gf / cm. 2In addition, distilled water was supplied to the platen as an auxiliary agent at a rate of 0.2 mL / min. The polishing time for the secondary chemical mechanical polishing (CMP) was 11 hours.

[0114] For comparison, the polishing rate and surface roughness were calculated for each of the primary mechanical polishing, secondary mechanical polishing, primary chemical mechanical polishing, and secondary chemical mechanical polishing processes. The polishing rates for primary mechanical polishing and secondary mechanical polishing were calculated using the same method as for the first polishing process in the above-described Examples and Comparative Examples. The polishing rates for primary chemical mechanical polishing and secondary chemical mechanical polishing were calculated using the same method as for the second polishing process in the above-described Examples and Comparative Examples. In comparison, primary mechanical polishing had a polishing rate of 15.1 μm / h and a surface roughness of 29.4 nm. In comparison, secondary mechanical polishing had a polishing rate of 2.1 μm / h and a surface roughness of 11.2 nm. In comparison, primary chemical mechanical polishing had a polishing rate of 0.3 μm / h and a surface roughness of 3.2 nm. In comparison, the secondary chemical mechanical polishing had a polishing rate of 0.1 μm / h and a surface roughness of 0.98 nm. The total polishing rate of the comparative example was 2.55 μm / h, and the polishing time required to reach a surface roughness of 1 nm or less was 22 hours. The method for calculating the total polishing rate was the same as in the above-mentioned Examples and Comparative Examples. The comparative example includes not only the polishing time but also the time required to replace the surface plate for each process, and when this time is included, the polishing rate becomes worse than the above value.

[0115] [Table 8]

[0116] (evaluation) If the polishing rate was higher than the control and the surface roughness was 1 nm or less, the evaluation was given as good (○); if the polishing rate was higher than the control and the surface roughness was 0.7 nm or less, the evaluation was given as excellent (◎); and if at least one of the conditions of the polishing rate being higher than the control and the surface roughness being 1 nm or less was not met, the evaluation was given as unacceptable (×).

[0117] In the Examples, the polishing time required to reduce the surface roughness to 1 nm or less was significantly shorter, and as shown in Tables 1 to 6, the Examples showed significantly improved polishing rates compared to the conventional methods shown in the comparative examples. As shown in Comparative Examples 1 to 3 in Table 7, when the pH of the first polishing liquid was 5.0 or less, the polishing rate was significantly reduced. It was found that when the pH of the first polishing liquid was set to 5.8 or higher, as in the Examples in Table 1, the surface roughness was reduced and the polishing rate was improved. Furthermore, as shown in Example 10 in Table 1, when the pH of the first polishing liquid was 10, the surface roughness was slightly increased, and it was found that the pH of the first polishing liquid should preferably be in the range of 5.8 to 8.5.

[0118] As shown in Comparative Examples 4 to 6 in Table 7, when the pH of the second polishing liquid is 6.0 or higher, the surface roughness decreases. When the pH of the second polishing liquid is set to 5.0 or lower, as in the Examples in Table 2, the surface roughness is reduced and the polishing rate is improved. Furthermore, as shown in Examples 11 to 13 in Table 2, when the pH of the second polishing liquid is 4.0 or higher, the surface roughness increases slightly. As shown in Example 20 in Table 2, when the pH of the second polishing liquid is 1.0, the surface roughness increases slightly. Therefore, it is clear that the pH of the second polishing liquid is preferably in the range of 2.0 to 3.0.

[0119] As shown in Examples 21 and 22 in Table 3, when the supply rate of the first polishing liquid is in the range of 0.1 ml / min to 10 ml / min, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 23 and 24 in Table 3, when the rotation speed of the platen in the first polishing step using the first polishing liquid is in the range of 10 rpm to 120 rpm, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 25 and 26 in Table 3, in the first polishing step using the first polishing liquid, the surface pressure of the wafer against the surface plate was 50 gf / cm 2 ~300gf / cm 2 It can be seen that within this range, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 27 and 28 in Table 3, when the supply rate of lactic acid solution in the first polishing step using the first polishing solution is in the range of 0.1 ml / min to 1.5 ml / min, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less.

[0120] As shown in Examples 29 and 30 in Table 4, when the supply rate of the second polishing liquid is in the range of 0.1 ml / min to 10 ml / min, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 31 and 32 in Table 4, when the rotation speed of the platen in the second polishing step using the second polishing liquid is in the range of 10 rpm to 120 rpm, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 33 and 34 of Table 4, in the second polishing step using the second polishing liquid, the surface pressure of the wafer against the surface plate was 50 gf / cm 2 ~300gf / cm 2 It can be seen that within this range, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 35 and 36 in Table 4, when the supply rate of lactic acid solution in the second polishing step using the second polishing solution is in the range of 0.1 ml / min to 1.5 ml / min, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less.

[0121] As shown in Examples 37 and 38 in Table 5, when the size (average particle diameter) of the abrasive particles used in the first polishing liquid is in the range of 5 μm to 800 μm, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 39 and 40 in Table 5, when the content of inorganic material contained in the abrasive particles used in the first polishing liquid is in the range of 1 wt% to 500 wt%, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 41 and 42 in Table 5, when the size (average particle diameter) of the inorganic material in the abrasive particles used in the first polishing liquid is in the range of 0.0005 μm to 50 μm, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 43 and 44 in Table 5, when the content of abrasive particles in the first polishing liquid is in the range of 0.02 wt% to 5 wt%, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 45 and 46 in Table 5, when the content of polysaccharide fiber in the first polishing liquid is in the range of 0.01 wt% to 5 wt%, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less.

[0122] As shown in Examples 47 and 48 in Table 6, when the size (average particle diameter) of the second abrasive used in the second polishing liquid is in the range of 5 nm to 10,000 nm, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 49 and 50 in Table 6, when the concentration of the second abrasive in the second polishing liquid is in the range of 0.1 wt% to 20 wt%, it is possible to improve the polishing rate and achieve a surface roughness of 1 nm or less. As shown in Examples 51 and 52 in Table 6, when the content of polysaccharide fiber in the second polishing liquid is in the range of 0.01 wt% to 5 wt%, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less. As shown in Examples 53 and 54 in Table 6, when the wavelength of the ultraviolet light irradiated in the second polishing step is in the range of 200 nm to 400 nm, it is possible to improve the polishing rate and reduce the surface roughness to 1 nm or less. As shown in Examples 55 and 56 in Table 6, the irradiation intensity of the ultraviolet light irradiated in the second polishing step was 5 mW / cm 2 ~5000mW / cm 2 It can be seen that within this range, the polishing rate can be improved and the surface roughness can be reduced to 1 nm or less.

Claims

1. a first polishing liquid containing chitosan particles carrying an inorganic material and adjusted to a pH of 5.8 or higher is supplied to a platen, and an object to be polished is polished on the platen; A second polishing liquid adjusted to a pH of 5.0 or less is supplied to the platen on which the chitosan particles are present, and the object to be polished is polished on the platen, thereby obtaining a polished product. A method for manufacturing a polished product, comprising:

2. the second polishing liquid contains a photocatalytic inorganic material; 2. The method for manufacturing a polished product according to claim 1, wherein the second polishing liquid supplied to the surface plate is irradiated with ultraviolet light.

3. 2. The method for manufacturing a polished product according to claim 1, wherein the surface plate is the same for polishing with the first polishing liquid and polishing with the second polishing liquid.

4. 2. The method for producing a polished product according to claim 1, wherein the first polishing liquid contains polysaccharide fiber.

5. 3. The method for producing a polished product according to claim 2, wherein the second polishing liquid contains polysaccharide fiber.

6. 2. The method for producing a polished product according to claim 1, wherein the chitosan particles are made of uncrosslinked chitosan.

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