Chemical mechanical polishing method based on piezoelectric light-assisted Fenton reaction and application

Abstract

The invention belongs to the related field of ultra-precision polishing technology, and discloses a chemical mechanical polishing method based on piezoelectric light-assisted Fenton reaction, which comprises the following steps: first-stage rough polishing processing: selecting particles of which the hardness is higher than or equal to that of a workpiece as a first abrasive material, putting the first abrasive material into deionized water to prepare a rough polishing solution, and then performing mechanical polishing; and in the second stage of fine polishing processing, the piezoelectric material serves as a second abrasive material and is put into deionized water, a photocatalyst is added, magnetic stirring is executed to prepare fine polishing liquid of a Fenton system, and then the fine polishing liquid is adopted and irradiated with ultraviolet light to execute chemical mechanical polishing. The invention further discloses ultra-precision polishing application of the method to monocrystalline silicon, silicon carbide, gallium nitride and diamond. Compared with the prior art, the method has the advantages that the material removal rate can be more effectively increased, the polishing time is shortened, a more environment-friendly polishing solution can be used, the waste liquid treatment cost is reduced, and the environment is protected.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision polishing technology, and more specifically, relates to a chemical mechanical polishing method and its application based on piezoelectric-assisted Fenton reaction. Background Technology

[0002] Chemical mechanical polishing (CMP) is a machining technique that relies on the synergistic effect of chemicals and machinery to remove material from the surface of a workpiece. It is also currently the only ultra-precision machining method capable of achieving local or even global planarization. Traditional Fenton-assisted chemical mechanical polishing technology uses hydrogen peroxide (H2O2) as an oxidant and various metal ions as catalysts, thus forming a homogeneous Fenton oxidation system.

[0003] This system must be placed in an acidic environment, often regulated with sulfuric acid or hydrochloric acid, and requires timely replenishment of H2O2 to sustain the Fenton reaction. This system poses varying degrees of harm to personnel, equipment, and the environment. Although solid-phase catalysts such as ferric hydroxide powder, iron(III) oxide (Fe3O4), cobalt(III) oxide (Co3O4), and manganese(III) oxide (MnO2) react with H2O2 to produce active hydroxyl groups (•OH), broadening the pH range of the polishing solution and ensuring catalyst recyclability, significantly reducing the release of metal ions into the environment, the transformation of the valence state of metal ions in the polishing solution remains a key factor limiting polishing efficiency and quality.

[0004] To address the aforementioned technical problems, some solutions have been proposed in the prior art. For example, CN116435189A and CN116589927A disclose methods for ultraviolet light-assisted chemical mechanical polishing and corresponding polishing slurries. However, the hole-electron pairs of a single ultraviolet laser are easily recombinated, and the energy utilization rate of ultraviolet light is low, resulting in a decrease in the efficiency of chemical action during the polishing process. In addition, CN109866084A discloses the introduction of iron salts and other substances into a photocatalytic medium to form an ultraviolet photocatalytic (Fenton-like) system. Although the chemical corrosion ability of this polishing slurry is enhanced to some extent, the oxidant in the polishing slurry is consumed while the valence state transformation of iron ions is slow, resulting in a continuous weakening of the subsequent oxidation ability, and the material removal efficiency during the polishing process is uneven.

[0005] Accordingly, there is an urgent need in this field to develop a novel, green, stable and efficient chemical mechanical polishing method in order to better solve the problem of ultra-precision polishing of high-hardness semiconductor materials such as single-crystal silicon, silicon carbide, gallium nitride and diamond. Summary of the Invention

[0006] To address one or more of the above-mentioned deficiencies or needs of existing technologies, this invention provides a chemical mechanical polishing method and application based on piezoelectric-optically assisted Fenton reaction. By redesigning the entire process route and reaction mechanism, compared with existing technologies, it can not only more effectively improve the material removal rate and reduce polishing time, but also use more environmentally friendly polishing fluid, reducing waste liquid treatment costs and protecting the environment. Therefore, it is particularly suitable for ultra-precision polishing applications of high-hardness semiconductors such as single-crystal silicon, silicon carbide, gallium nitride, and diamond, while achieving low-damage and ultra-smooth surfaces.

[0007] To achieve the above objectives, according to one aspect of the present invention, a chemical mechanical polishing method based on piezoelectric-assisted Fenton reaction is provided, the method comprising the following two stages: Phase 1: Rough Polishing Select particles with a hardness higher than or equal to that of the workpiece as the first abrasive, put them into deionized water to prepare a coarse polishing solution, and then use the coarse polishing solution to perform mechanical polishing on the workpiece. Second stage: Fine polishing A piezoelectric material was used as the second abrasive. It was placed in deionized water and a photocatalyst was added. Then, magnetic stirring was performed to prepare a Fenton system fine polishing slurry. Next, the fine polishing slurry was transported to the surface of the workpiece to make contact, and the fine polishing slurry was irradiated with external ultraviolet light. During this process, the piezoelectric material in the fine polishing slurry is subjected to various mechanical stresses, thereby achieving a piezoelectric catalytic effect, i.e., generating an internal electric field (IEF), which drives e - and h + The migration towards the surface of the second abrasive simultaneously triggers redox reactions to form hydroxyl radicals (•OH) and superoxide anion radicals (•O2). - The photocatalyst in the polishing slurry, when excited by ultraviolet light, exhibits a photocatalytic effect, releasing electron-hole pairs that react with surface hydroxyl radicals (-OH) and water molecules to generate active oxide species such as hydroxyl radicals (•OH). In this way, the piezoelectric catalytic effect and the photocatalytic effect are coupled together. The built-in electric field enhances the utilization rate of ultraviolet light by the polishing slurry and accelerates the valence state cycle of metal ions in the Fenton system, thereby forming an oxide layer on the surface of the workpiece. This layer is subsequently removed by the second abrasive mechanically, resulting in a low-damage, ultra-smooth surface.

[0008] As a further preferred embodiment of the present invention, in the above-mentioned rough polishing stage, the first abrasive is preferably made of alumina or diamond particles, with an average particle size of W 0.5 to W 1.0, and its mass fraction in the rough polishing liquid is preferably 3.0 wt.% to 6.0 wt.%.

[0009] As a further preferred embodiment of the present invention, in the above-mentioned fine polishing stage, the piezoelectric material is selected from modified piezoelectric zirconium oxide, tetragonal barium titanate, zinc oxide or molybdenum disulfide particles, and its average particle size is preferably between 0.05 micrometers and 1.0 micrometers.

[0010] As a further preferred embodiment of the present invention, in the above-mentioned fine polishing stage, the photocatalyst is selected from BiFeO3 or Bi2Fe4O9.

[0011] As a further preferred embodiment of the present invention, in the above-mentioned fine polishing stage, the various mechanical stresses include one or a combination of the stresses of stirring, water flow, friction, extrusion and ultrasound.

[0012] As a further preferred embodiment of the present invention, the fine polishing liquid may also contain a dispersant and / or a pH adjuster, wherein the dispersant is selected from xanthan gum, sodium citrate, sodium carboxymethyl cellulose, sorbitol, polyethylene glycol or silica sol; and the pH adjuster is selected from citric acid, tartaric acid, malic acid or mandelic acid.

[0013] As a further preferred embodiment of the present invention, hydrogen peroxide (H2O2) may preferably be added to the fine polishing solution as an oxidant to improve the effect of the Fenton reaction.

[0014] As a further preferred embodiment of the present invention, the fine polishing slurry is preferably prepared through the following process: Fill a container with deionized water, place a magnet in the container and let it sink to the bottom; then place the container on a magnetic stirrer, start the magnetic stirrer and adjust the speed of the magnet. At this time, the liquid in the container is stirred to form a vortex. The piezoelectric material is added to the container as a second abrasive, and after thorough stirring, the photocatalyst is added and stirring continues, thereby preparing the fine polishing liquid.

[0015] As a further preferred embodiment of the present invention, the fine polishing process is preferably achieved through the following steps: The polishing pad is attached to the polishing disc, and then the workpiece is fixed to the bottom of the polishing head, with the weight of the polishing head serving as the load on the workpiece relative to the polishing pad. A rotary motor rotates the polishing disc and the polishing pad adhered thereon. A peristaltic pump continuously delivers the fine polishing slurry prepared in the container to the polishing pad. Simultaneously, an ultraviolet lamp irradiates the processing area of ​​the workpiece. During this process, the rotating polishing pad rapidly distributes the fine polishing slurry across its entire surface. The slurry flowing between the workpiece and the polishing pad is then transported to the processing area of ​​the workpiece. This process generates an internal electric field under the action of various mechanical stresses, and simultaneously releases electron-hole pairs upon ultraviolet excitation. The formation of the piezoelectric field further promotes photoinduced carrier separation and migration, enhancing the oxidizing activity of the polishing slurry.

[0016] According to another aspect of the present invention, the above method is also provided for ultra-precision polishing of high-hardness semiconductors such as single-crystal silicon, silicon carbide, gallium nitride, and diamond.

[0017] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: 1. This invention addresses the various shortcomings of existing chemical mechanical polishing processes by redesigning the entire process route and reaction mechanism. It can fully utilize the energy of mechanical-optical processes to generate an internal electric field during polishing to improve photocatalytic efficiency, while accelerating the valence state cycle of metal ions. Furthermore, the various active hydroxyl oxides generated in situ can appropriately supplement the Fenton system consumed during the reaction process, ensuring the continuous and stable oxidation process of the workpiece by the polishing solution, and effectively improving the material removal rate of the workpiece. 2. The present invention further makes targeted improvements to some specific operations of the polishing process in terms of supporting workpieces and key parameters, so as to complete the entire chemical mechanical polishing process in a way that is easy to control and efficient, and ensure the mutual coupling of piezoelectric catalysis and photocatalysis effects; 3. The process method of the present invention can catalytically oxidize the workpiece in situ while mechanically grinding it away, thereby reducing the brittleness of the material surface and improving the plastic removal effect of the abrasive. Therefore, as a green, stable and efficient technical solution, it is especially suitable for ultra-precision polishing applications of high-hardness semiconductors such as single-crystal silicon, silicon carbide, gallium nitride and diamond, while achieving a low-damage and ultra-smooth surface. Attached Figure Description

[0018] Figure 1 This is an overall process flow diagram of the chemical mechanical polishing method based on piezoelectric-optically assisted Fenton reaction according to the present invention; Figure 2 This is a schematic diagram of the composition of a polishing apparatus according to a preferred embodiment of the present invention; Figure 3 Taking 200nm single-crystal silicon as an example, this paper demonstrates its three-dimensional surface morphology after rough polishing. Figure 4 Taking 200nm single-crystal silicon as an example, this paper demonstrates its three-dimensional surface morphology after fine polishing. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Figure 1 This is a flowchart of the overall process of the chemical mechanical polishing method based on piezoelectric-optically assisted Fenton reaction according to the present invention, which will be referred to below. Figure 1 The process method of the present invention will be explained in more detail below.

[0021] The chemical mechanical polishing method according to the present invention mainly includes the following two stages of operation. Phase 1: Rough Polishing Select particles with a hardness higher than or equal to that of the workpiece as the first abrasive, put them into deionized water to prepare a coarse polishing solution, and then use the coarse polishing solution to perform mechanical polishing on the workpiece. According to a preferred embodiment of the present invention, in the above-mentioned rough polishing stage, the first abrasive is preferably made of alumina or diamond particles, with an average particle size of W 0.5 to W 1.0, and its mass fraction in the rough polishing liquid is preferably 3.0 wt.% to 6.0 wt.%.

[0022] More specifically, in the rough polishing stage, abrasives with a hardness higher than or equivalent to that of the workpiece can be selected, such as single-crystal silicon, which is most suitable for rough polishing of alumina. The particle size is mostly selected in the range of W 0.5 ~ W 1.0. The prepared polishing solution contains only alumina and deionized water, and the mass fraction of alumina is preferably between 3.0 wt.% and 6.0 wt.%. For silicon carbide, gallium nitride, or diamond, diamond micro powder is most suitable for rough polishing, and the polishing solution can be adjusted to alkaline.

[0023] Second stage: Fine polishing Using piezoelectric material as the second abrasive, it is placed in deionized water and a photocatalyst is added. Then, magnetic stirring is performed to prepare a Fenton system fine polishing slurry. Next, the fine polishing slurry is transported to the surface of the workpiece to make contact, and the fine polishing slurry is irradiated with external ultraviolet light.

[0024] During this process, the piezoelectric material in the fine polishing slurry is subjected to various mechanical stresses (such as stirring, water flow, friction, extrusion, or ultrasound) to obtain a piezoelectric catalytic effect, that is, to generate an internal electric field (IEF), driving e - and h + The migration towards the surface of the second abrasive simultaneously triggers redox reactions to form hydroxyl radicals (•OH) and superoxide anion radicals (•O2). - The photocatalyst in the polishing slurry, when excited by ultraviolet light, exhibits a photocatalytic effect, releasing electron-hole pairs that react with surface hydroxyl radicals (-OH) and water molecules to generate active oxide species such as hydroxyl radicals (•OH). In this way, the piezoelectric catalytic effect and the photocatalytic effect are coupled together. The built-in electric field enhances the utilization rate of ultraviolet light by the polishing slurry, while accelerating the valence state cycle of metal ions in the Fenton system and continuously modulating carrier dynamics. In the polishing liquid environment, various active oxide species can be continuously and stably generated, forming an oxide layer on the surface of the workpiece. This layer is subsequently removed by the second abrasive mechanically, resulting in a low-damage, ultra-smooth surface.

[0025] According to another preferred embodiment of the present invention, in the above-mentioned fine polishing stage, the piezoelectric material is selected from modified piezoelectric zirconium oxide, tetragonal barium titanate, zinc oxide, or molybdenum disulfide particles, and its average particle size is preferably between 0.05 micrometers and 1.0 micrometers. Furthermore, the photocatalyst is selected from BiFeO3 or Bi2Fe4O9.

[0026] More specifically, the aforementioned fine polishing stage is a type of chemical mechanical polishing. The polishing slurry, as the direct carrier for realizing the piezoelectric-assisted Fenton reaction-based chemical mechanical polishing method, has a particularly important composition. Commonly used polishing abrasives include diamond, alumina, silicon dioxide, and cerium oxide, but these abrasives do not possess piezoelectric effects. Therefore, in this invention, modified piezoelectric zirconium oxide or tetragonal barium titanate can be used as the abrasive, with a particle size distribution of 0.05 mm. ~1.0 between.

[0027] More specifically, in actual operation, the selected abrasives can be slowly added to a beaker containing deionized water. The magnetic stirrer is turned on, the speed is adjusted and stirred for a certain period of time to disperse the abrasives evenly. A small amount of photocatalyst and metal salt are added, and the mixture is stirred thoroughly again for a certain period of time. Finally, a certain amount of hydrogen peroxide (H2O2, 30 wt.%) is added as an oxidant. Finally, some weak acids and weak bases are used to adjust the pH environment of the polishing solution. If necessary, dispersants (xanthan gum, sodium carboxymethyl cellulose, sodium citrate, sorbitol, polyethylene glycol or silica sol, etc.) may also be added.

[0028] During this process, physical stirring maintains the dispersion characteristics of particles in the polishing slurry. A peristaltic pump and conduit drop the polishing slurry onto the polishing pad. In the processing area, the rotating polishing disc causes the piezoelectric abrasive to generate an internal electric field due to friction and compressive stress. For example, ultraviolet light with a wavelength of 365nm excites the photocatalyst to release electron-hole pairs. The piezoelectric field enhances the utilization rate of ultraviolet light by the polishing slurry and can also promote the valence state cycle of metal ions to enhance the stability and persistence of the Fenton-like oxidation of the polishing slurry. An oxide layer is formed on the surface of the workpiece after Fenton-like oxidation, which is subsequently mechanically removed by the piezoelectric abrasive.

[0029] The following will use a single-crystal silicon with a diameter of 200nm as an example to provide further explanation of the present invention.

[0030] Specific example 1 Single-crystal silicon with a diameter of 200 mm is selected as the workpiece, which is most suitable for rough polishing of alumina. The particle size is usually selected between W0.5 and W1.0. The prepared rough polishing solution contains only alumina and deionized water, with the mass fraction of alumina between 3.0 wt.% and 6.0 wt.%. After polishing for a certain period of time, its surface morphology is as follows. Figure 3 As shown, the surface roughness is 3.712 nm.

[0031] After rough polishing, the fine polishing operation for this single-crystal silicon workpiece is as follows: Step 1: Add 200mL of deionized water to beaker 14, place magnet 13 into beaker 14 and let it sink to the bottom, then place beaker 14 on magnetic stirrer 12, turn on magnetic stirrer 12 and adjust the speed of magnet 13 to 800 rpm to 1200 rpm. At this time, the liquid in beaker 14 will be stirred to form a vortex. Add piezoelectric materials as abrasives, such as modified piezoelectric zirconium oxide, tetragonal barium titanate, zinc oxide and molybdenum disulfide.

[0032] In this specific example, piezoelectric zirconium oxide with a particle size of 80 nm can be selected as the abrasive. 20 g is weighed and added to beaker 14. After stirring thoroughly for 30 min, a photocatalyst in the form of a metal salt needs to be added. Since BiFeO3 and Bi2Fe4O9 have the effects of photocatalyst and Fenton-like catalyst, 50 nm to 80 nm BiFeO3 can be added in this specific example. The mass fraction of BiFeO3 in the polishing solution is 0.5 wt.%, that is, 2.5 g is added to 500 mL of polishing solution. Stir again for 30 min, add 100 g of hydrogen peroxide (H2O2, 30 wt.%) to enhance the Fenton reaction effect. Finally, add deionized water to the 500 mL mark of beaker 14. The pH environment can be adjusted to acidic by choosing organic weak acids such as citric acid, tartaric acid, malic acid or mandelic acid. In order to improve the dispersibility of particles in the polishing solution, a certain amount of silica sol can be added as a dispersant, which can avoid the consumption of oxide species in the polishing solution by organic dispersants.

[0033] Step Two: Fix foot 1 to the bottom of the polishing device 2 to support the entire polishing device. The rotary motor 3 is placed inside the main body of the polishing device 2, and the lower part of the polishing disc 5 is connected to the rotary motor 3. Select a polishing pad 6, choosing a suitable pad based on the characteristics of the material being processed. For example, for monocrystalline silicon, a polishing pad made of frosted leather or damping cloth can be used. Then, attach the polishing pad 6 to the polishing disc 5, ensuring a tight fit without any obvious air bubbles. The workpiece 7 is then fixed to the bottom of the fused silica polishing head 8. The weight of the fused silica polishing head 8 is the load on the workpiece 7. The ultraviolet lamp 9 is placed on the top of the main body of the polishing device 2 and shines vertically downwards on the polishing disc 5. The wavelength of the ultraviolet light can be selected as 365 nm, and its power is 60 W and the range is adjustable. The emitted ultraviolet light can pass through the fused silica polishing head 8 and act directly on the processing area. The power switch 10 controls the start of the rotary motor 3, and the speed control knob 11 controls the rotation speed of the polishing disc 5. The magnetic stirrer 12 stirs the polishing liquid 15 in the beaker 14 through the magnetic stirrer 13. The conduit 16 is connected to the polishing liquid 15 and the peristaltic pump 17. After the power is turned on, the peristaltic pump 17 controls the flow rate of the polishing liquid 15 through the speed control knob and is gradually transported to the polishing pad 6. During the polishing process, the rotating polishing disc 5 transports the polishing liquid 15 on the surface of the polishing pad 6 to the area of ​​the workpiece 7. The polishing waste liquid will flow to the waste liquid collection tank 4.

[0034] Step 3: During processing, turn on the power switch 10 and use the adjustment knob 11 to maintain the polishing disc speed at 50 rpm to 80 rpm. Start the polishing slurry supply system. The conduit 16 connects the polishing slurry 15 to the peristaltic pump 17. After the power is turned on, the peristaltic pump 17 controls the flow rate of the polishing slurry 15 through the speed adjustment knob, gradually delivering it to the polishing pad 6. Under the action of centrifugal force, the delivered polishing slurry 15 is quickly distributed across the entire surface of the polishing pad 6. The polishing slurry flowing between the workpiece 7 and the polishing pad 6 is subjected to mechanical friction and ultraviolet light, which rapidly oxidizes the surface of the workpiece 7. The piezoelectric zirconium oxide comes into contact with the workpiece 7 and the surface charge is polarized due to friction. This in-situ catalytic generation of more active hydroxyl and other oxide species in the polishing slurry to replenish the consumption of the reaction, while the surface charge transfer also accelerates the Fe in the polishing slurry. 3+ / Fe 2+ The cycle promotes the Fenton process, and finally the oxide film on the surface of workpiece 7 is removed by piezoelectric zirconium oxide mechanical grinding.

[0035] After polishing for the appropriate time, turn off all power to the device, remove the workpiece from the bottom of the polishing head, rinse it first with deionized water, and then gently wipe the workpiece surface with a non-woven cloth soaked in anhydrous ethanol. The surface morphology of the workpiece is measured after chemical mechanical polishing. For example... Figure 4 As shown, its roughness is less than 0.2 nm, and the entire processing is clean, efficient, simple and safe to operate.

[0036] In summary, the piezoelectric-optically assisted Fenton reaction-based chemical mechanical polishing method of the present invention can fully utilize the energy of the mechanical-optical process to generate an internal electric field during polishing to improve photocatalytic efficiency and accelerate the valence state cycle of metal ions. Moreover, the various active hydroxyl oxides generated in situ can appropriately replenish the Fenton system consumed during the reaction process, ensuring the continuous and stable oxidation process of the workpiece by the polishing slurry, and effectively improving the material removal rate of the workpiece. In addition, a more environmentally friendly polishing slurry can be used, reducing waste liquid treatment costs and protecting the environment. Therefore, as a green, stable, and efficient technical solution, it is particularly suitable for ultra-precision polishing applications of high-hardness semiconductors such as single-crystal silicon, silicon carbide, gallium nitride, and diamond, while achieving low-damage and ultra-smooth surfaces.

[0037] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A chemical mechanical polishing method based on piezoelectric-assisted Fenton reaction, characterized in that, This method includes the following two phases of operation: Phase 1: Rough Polishing Select particles with a hardness higher than or equal to that of the workpiece as the first abrasive, put them into deionized water to prepare a coarse polishing solution, and then use the coarse polishing solution to perform mechanical polishing on the workpiece. Second stage: Fine polishing A piezoelectric material was used as the second abrasive. It was placed in deionized water and a photocatalyst was added. Then, magnetic stirring was performed to prepare a Fenton system fine polishing slurry. Next, the fine polishing slurry was transported to the surface of the workpiece to make contact, and the fine polishing slurry was irradiated with external ultraviolet light. During this process, the piezoelectric material in the fine polishing slurry is subjected to various mechanical stresses, thereby achieving a piezoelectric catalytic effect, i.e., generating an internal electric field (IEF), which drives e - and h + The migration towards the surface of the second abrasive simultaneously triggers redox reactions to form hydroxyl radicals (•OH) and superoxide anion radicals (•O2). - The photocatalyst in the polishing slurry, when excited by ultraviolet light, exhibits a photocatalytic effect, releasing electron-hole pairs that react with surface hydroxyl radicals (-OH) and water molecules to generate active oxide species such as hydroxyl radicals (•OH). In this way, the piezoelectric catalytic effect and the photocatalytic effect are coupled together. The built-in electric field enhances the utilization rate of ultraviolet light by the polishing slurry and accelerates the valence state cycle of metal ions in the Fenton system, thereby forming an oxide layer on the surface of the workpiece. This layer is subsequently removed by the second abrasive mechanically, resulting in a low-damage, ultra-smooth surface.

2. The method as described in claim 1, characterized in that, In the above-mentioned rough polishing stage, the first abrasive is preferably made of alumina or diamond particles, with an average particle size of W 0.5 to W 1.0, and its mass fraction in the rough polishing liquid is preferably 3.0 wt.% to 6.0 wt.%.

3. The method as described in claim 2, characterized in that, In the aforementioned fine polishing stage, the piezoelectric material is selected from modified piezoelectric zirconium oxide, tetragonal barium titanate, zinc oxide, or molybdenum disulfide particles, and its average particle size is preferably between 0.05 micrometers and 1.0 micrometers.

4. The method as described in claim 3, characterized in that, In the above-mentioned fine polishing stage, the photocatalyst is selected from BiFeO3 or Bi2Fe4O9.

5. The method as described in claim 4, characterized in that, During the aforementioned fine polishing stage, the various mechanical stresses include one or a combination of stresses such as stirring, water flow, friction, extrusion, and ultrasound.

6. The method according to any one of claims 1-5, characterized in that, The fine polishing solution may preferably also contain a dispersant and / or a pH adjuster, wherein the dispersant is selected from xanthan gum, sodium citrate, sodium carboxymethyl cellulose, sorbitol, polyethylene glycol, or silica sol; and the pH adjuster is selected from citric acid, tartaric acid, malic acid, or mandelic acid.

7. The method as described in claim 6, characterized in that, The fine polishing solution shown may preferably also contain hydrogen peroxide (H2O2) as an oxidant to improve the effect of the Fenton reaction.

8. The method according to any one of claims 1-5, characterized in that, The fine polishing slurry is preferably prepared through the following process: Fill a container with deionized water, place a magnet in the container and let it sink to the bottom; then place the container on a magnetic stirrer, start the magnetic stirrer and adjust the speed of the magnet. At this time, the liquid in the container is stirred to form a vortex. The piezoelectric material is added to the container as a second abrasive, and after thorough stirring, the photocatalyst is added and stirring continues, thereby preparing the fine polishing liquid.

9. The method as described in claim 8, characterized in that, The fine polishing process is preferably achieved through the following steps: The polishing pad is attached to the polishing disc, and then the workpiece is fixed to the bottom of the polishing head, with the weight of the polishing head serving as the load on the workpiece relative to the polishing pad. A rotary motor rotates the polishing disc and the polishing pad adhered thereon. A peristaltic pump continuously delivers the fine polishing slurry prepared in the container to the polishing pad. Simultaneously, an ultraviolet lamp irradiates the processing area of ​​the workpiece. During this process, the rotating polishing pad rapidly distributes the fine polishing slurry across its entire surface. The slurry flowing between the workpiece and the polishing pad is then transported to the processing area of ​​the workpiece. This process generates an internal electric field under the action of various mechanical stresses, and simultaneously releases electron-hole pairs upon ultraviolet excitation. The formation of the piezoelectric field further promotes photoinduced carrier separation and migration, enhancing the oxidizing activity of the polishing slurry.

10. The method described in any one of claims 1-9 for ultra-precision polishing applications of high-hardness semiconductors such as single-crystal silicon, silicon carbide, gallium nitride, and diamond.

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