Chemical mechanical polishing solution based on Bi-CaZnOS mechanoluminescence catalyst, catalytic performance verification method and application of chemical mechanical polishing solution in SiC chip polishing

Abstract

The invention relates to the technical field of semiconductor processing, in particular to a chemical mechanical polishing solution based on a Bi-CaZnOS mechanoluminescent catalyst, a catalytic performance verification method and application of the chemical mechanical polishing solution in SiC chip polishing. The polishing solution comprises a Bi-CaZnOS mechanoluminescent material, a TiO2 photocatalyst and a dispersion medium, wherein the mass ratio of the Bi-CaZnOS mechanoluminescent material to the TiO2 photocatalyst is (1.5-3.5): 1, the signal-to-noise ratio is improved by innovative material design and Li < + >-assisted Bi < 3 + >-doped CaZnOS mechanoluminescent material, the emission wave band is regulated and controlled to a 480-500nm blue-green visible light region, the luminous intensity is improved by about 3 times compared with that of the material reported in the existing literature, meanwhile, the preparation temperature is reduced to 990 DEG C, and the preparation cost is reduced. And compared with the traditional process (1200 DEG C), the energy consumption and the environmental pollution are obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, specifically to a chemical mechanical polishing slurry based on Bi-CaZnOS mechanoluminescent catalyst, a method for verifying catalytic performance, and its application in SiC chip polishing. Background Technology

[0002] Silicon carbide (SiC), as an outstanding representative of the new generation of wide bandgap semiconductor materials, has a wide bandgap (3.26 eV) and a high breakdown electric field (2.2 × 10⁻⁶ eV). 6 V / cm, high thermal conductivity (4.9 W / cm·K) and high electron saturation velocity (2×10⁻⁶). 7 With its superior properties such as high hardness (cm / s), SiC has become a core power device material for strategic emerging industries such as new energy vehicles, 5G communications, aerospace, and rail transportation. As the global electric vehicle market rapidly expands, the demand for SiC power devices is experiencing explosive growth, and the global SiC device market size is expected to exceed US$10 billion by 2027. However, SiC material has a Mohs hardness of 9.2-9.5 (second only to diamond), coupled with its extremely high chemical stability (it hardly reacts with any chemical reagents at room temperature), posing a severe challenge to the precision polishing process in chip manufacturing.

[0003] The core issues currently facing SiC chip polishing can be summarized as follows:

[0004] First, traditional chemical mechanical polishing (CMP) technology is inefficient, hindering industry development. Current SiC polishing processes primarily rely on strong oxidants such as potassium permanganate (KMnO4) or hydrogen peroxide (H2O2) for chemical oxidation, followed by mechanical grinding to remove the oxide layer. However, this "spatiotemporal separation" of chemical and mechanical actions leads to a severe efficiency bottleneck: chemical oxidation requires a certain reaction time and diffusion process, while mechanical grinding is an instantaneous action. The two cannot be performed synchronously, resulting in oxide layer accumulation and a material removal rate (MRR) typically less than 100 nm / h, an order of magnitude lower than the polishing efficiency of silicon wafers (>500 nm / h).

[0005] Secondly, the chemical pollution problem of traditional strong oxidant polishing slurries is becoming increasingly prominent. Taking potassium permanganate polishing slurry as an example, it generates a large amount of manganese-containing wastewater during the polishing process. Manganese ions, as heavy metals, have bioaccumulation and neurotoxicity, and wastewater treatment is costly and poses environmental risks. In addition, high concentrations of H2O2 (typically >5wt%) easily cause metal contamination (such as Fe and Cu ions) during polishing. Once these impurities enter the SiC surface or subsurface, they will form deep-level defect centers, seriously affecting the breakdown voltage and carrier mobility of the device. The use of traditional oxidants is also accompanied by problems such as surface corrosion pits and subsurface damage layers, reducing the reliability and lifespan of the chip.

[0006] Third, in traditional CMP processes, over 90% of the mechanical energy is dissipated as heat, resulting in extremely low energy efficiency. During the frictional contact between the abrasive and the SiC surface, a significant amount of mechanical energy is converted into heat and lost, not only wasting energy but also causing an increase in polishing temperature, affecting the controllability of the chemical reaction and the stability of the polishing slurry. How to efficiently utilize the mechanical energy in the CMP process and convert it into an effective driving force for the chemical reaction has become a pressing scientific problem in the field.

[0007] Fourth, existing photocatalytic-assisted polishing technologies have significant limitations. Although CN109866084A discloses a UV photocatalytic-assisted chemical mechanical polishing device and method that uses an external ultraviolet light source to excite a photocatalyst to generate active oxide species, this approach requires additional ultraviolet light source equipment, complex optical path design, and light-shielding protection measures, increasing equipment complexity and operating costs. More importantly, there is a spatial distance between the external light source and the polishing contact point, resulting in low light energy utilization efficiency, and ultraviolet light has an aging and degradation effect on some polymer polishing pad materials.

[0008] Fifth, the performance and preparation process of existing mechanoluminescent materials are insufficient to meet the requirements of polishing applications. CN111909689A discloses a Bi-doped CaZnOS mechanoluminescent composite material, its preparation method, and its application, and studies the mechanoluminescent characteristics of Bi³⁺ as the luminescent center. However, this technology has the following shortcomings: First, the traditional preparation process requires high-temperature sintering exceeding 1200℃, which consumes a lot of energy, and Bi³⁺ ions volatilize severely at high temperatures, resulting in an actual doping rate of less than 65% of the theoretical value, thus limiting the luminescence efficiency; Second, during long-term high-temperature sintering, the ZnS component decomposes and releases toxic H2S gas, causing serious environmental pollution and safety hazards; Third, the emission wavelength of existing materials is usually located in the infrared to near-infrared region (>600nm), which has a low matching degree with the absorption band of commonly used photocatalysts, making it difficult to effectively excite photocatalytic reactions.

[0009] In summary, existing technologies face multiple bottlenecks, including low efficiency, high pollution, and high energy consumption, necessitating the development of a novel catalytic system. This system should possess the following characteristics: it should enable efficient in-situ conversion of mechanical energy into chemical energy; the generated light energy should have good bandgap matching with commercial photocatalysts; the preparation process should be simple, low-temperature, and environmentally friendly; and the polishing process should be intelligently controlled by feedback. Based on these requirements, this invention proposes a novel polishing technology solution based on mechanoluminescence-photocatalysis coupling. Summary of the Invention

[0010] The purpose of this invention is to provide a chemical mechanical polishing slurry based on Bi-CaZnOS mechanoluminescent catalyst, a method for verifying catalytic performance, and its application in SiC chip polishing. Through the mechanoluminescence-photocatalysis coupling mechanism, the mechanical energy in the CMP process is converted into photochemical energy in situ, realizing closed-loop efficient utilization of energy, while improving the polishing efficiency and surface quality of SiC chips.

[0011] To achieve the above objectives, the present invention provides a chemical mechanical polishing slurry based on a Bi-CaZnOS mechanoluminescent catalyst, wherein the polishing slurry comprises a Bi-CaZnOS mechanoluminescent material, a TiO2 photocatalyst, and a dispersion medium, wherein the mass ratio of the Bi-CaZnOS mechanoluminescent material to the TiO2 photocatalyst is 1.5-3.5:1.

[0012] Preferably, the mass ratio of the Bi-CaZnOS mechanoluminescent material to the TiO2 photocatalyst is 2.5:1.

[0013] Preferably, the polishing liquid further includes Al2O3 or SiO2 abrasive, the particle size of which is 0.1-1.0 μm.

[0014] The Bi-CaZnOS metronome material of the present invention is prepared by the following method:

[0015] (1) First, mix the raw materials according to the molar ratio of CaCO3:ZnS:Bi2O3:Li2CO3=0.9-1.0:1:0.03-0.07:0.05-0.15;

[0016] (2) Next, anhydrous ethanol is added and the mixture is ground and dispersed to form a uniformly mixed precursor;

[0017] (3) Then, the precursor is dried at 80-100°C;

[0018] (4) Next, under a nitrogen protective atmosphere, the dried precursor is sintered at 900-1050℃ for 2-4 hours;

[0019] (5) Finally, after the furnace is naturally cooled to room temperature, it is taken out and ground to obtain the Bi-CaZnOS mechanoluminescent material.

[0020] In a preferred embodiment of the present invention, the molar ratio of CaCO3:ZnS:Bi2O3:Li2CO3 is 0.95:1:0.05:0.10.

[0021] Further, in step (2), the grinding and dispersion time is 30-60 minutes; in step (3), the drying time is 3-5 hours; in step (4), the sintering temperature is 990℃ and the sintering time is 3 hours; in step (5), the grinding time is 15-30 minutes.

[0022] This invention also provides a method for verifying the catalytic performance of the above-mentioned chemical mechanical polishing slurry, the verification method comprising the following steps:

[0023] (1) First, Al2O3 or SiO2 small balls are placed in the ball mill as stress sources;

[0024] (2) Next, add methylene blue solution and the catalyst to be tested to the ball mill;

[0025] (3) Then, start the ball mill and run it at the predetermined speed for the predetermined time;

[0026] (4) Finally, the degradation rate of methylene blue was measured to evaluate the catalytic efficiency of the catalyst.

[0027] Preferably, the ball mill rotates at a speed of 400-500 r / min, the initial concentration of the methylene blue solution is 5-20 mg / L, and the predetermined time is 30-180 minutes.

[0028] This invention also provides a method for applying the above-mentioned chemical mechanical polishing slurry in the polishing of SiC chips, the method comprising the following steps:

[0029] (1) First, the chemical mechanical polishing slurry is applied to the polishing pad;

[0030] (2) Next, the SiC chip is brought into contact with the polishing pad;

[0031] (3) Then, pressure is applied to make the SiC chip move relative to the polishing pad;

[0032] (4) At the same time, the intensity of the 480nm wavelength light emitted by the Bi-CaZnOS material is monitored in real time;

[0033] (5) Finally, the polishing pressure is adjusted in real time based on the light intensity signal.

[0034] Preferably, the polishing pressure is 0.5-5 psi, the relative motion speed is 30-120 rpm, and the polishing time is 5-30 minutes; wherein, when the intensity of the 480nm wavelength light is lower than a preset threshold, the polishing pressure is increased; when the intensity of the 480nm wavelength light is higher than the preset threshold, the polishing pressure is decreased.

[0035] The present invention has the following beneficial effects:

[0036] 1. This invention innovatively achieves precise bandgap matching between blue light emission and TiO2 photocatalyst. In the field of mechanoluminescent materials, the emission wavelengths of most materials are located in the red to near-infrared region (>600nm), while mechanoluminescent materials capable of producing blue light (<500nm) are extremely scarce. This invention, through a Li⁺-assisted Bi³⁺ doping strategy, innovatively tunes the emission band of CaZnOS-based materials to the 480-500nm blue-green visible light region. This band precisely matches the absorption band of commercially available N-type TiO2 photocatalysts (anatase type, bandgap 3.2eV, corresponding absorption edge approximately 388nm). TiO2, as the most extensively researched and commercially available photocatalyst material globally, possesses significant advantages such as low cost, good chemical stability, non-toxicity, environmental friendliness, and high photocatalytic activity. This invention innovatively couples scarce blue mechanoluminescent materials with mature TiO2 photocatalysts to construct a highly efficient energy conversion chain of mechanical energy → light energy → chemical energy, realizing a synergistic catalytic system with three coupled fields of force, light, and chemistry.

[0037] 2. The Li⁺-assisted doping strategy significantly enhances the mechanoluminescence performance. This invention innovatively introduces Li⁺ as an auxiliary dopant ion, significantly enhancing the mechanoluminescence performance of Bi-CaZnOS materials through the following mechanisms: First, Li⁺ (ionic radius 0.76 Å) enters the CaZnOS lattice to fill Ca²⁺ (ionic radius 1.00 Å) vacancies, reducing non-radiative recombination centers and improving the luminescence quantum efficiency; second, Li⁺ doping optimizes the piezoelectric properties of the lattice, greatly improving the material's sensitivity to mechanical stress; and third, the introduction of Li⁺ promotes the effective activation of Bi³⁺ luminescent centers. Experimental results show that the optimized Li⁺-assisted Bi³⁺-doped CaZnOS material exhibits approximately three times higher mechanoluminescence intensity than the non-Li⁺-doped material reported in existing literature, achieving a performance breakthrough in the field of stress-luminescent materials.

[0038] 3. Low-Temperature Preparation Process Enables Green and Low-Carbon Manufacturing. This invention significantly reduces the diffusion barrier of Bi³⁺ into the CaZnOS lattice through a Li⁺-assisted doping strategy, thereby lowering the sintering temperature from 1200℃ in the traditional process to 990℃, a reduction of over 200℃. This low-temperature process brings multiple benefits: First, the actual Bi³⁺ doping rate increases from approximately 65% ​​in the traditional process to over 90%, significantly improving luminous efficiency; second, energy consumption is greatly reduced, calculated based on the fourth power relationship between heat and temperature, resulting in a reduction of approximately 50%; third, the ZnS composition is more stable at low temperatures, significantly reducing the release of toxic gases such as H₂S, greatly improving environmental friendliness.

[0039] 4. A highly efficient energy conversion mechanism of mechanoluminescence-photocatalysis coupling was established. In the traditional CMP process, over 90% of the mechanical energy generated by friction between the abrasive and the SiC surface is dissipated as heat. This invention utilizes a mechanoluminescence-photocatalysis coupling mechanism to convert this portion of mechanical energy in situ into effective photochemical energy: under mechanical stress, the Bi-CaZnOS material exhibits an intensity exceeding 10... 6 A piezoelectric field of V / m drives charge separation and excites Bi³⁺ luminescent centers to emit 480-500nm blue-green light. This blue-green light is absorbed by TiO₂ nanoparticles, exciting the generation of highly active electron-hole pairs, which in turn form strongly oxidizing reactive oxygen species (·OH, ·O₂⁻, etc.). These species target and attack the Si-C bonds on the SiC surface, lowering the surface energy barrier and accelerating the chemical reaction process. Through this innovative mechanism, the effective utilization rate of mechanical energy is increased by more than 10 times, and the SiC material removal rate reaches 287±12nm / h, which is nearly 3 times that of traditional methods.

[0040] 5. A self-feedback intelligent polishing system was developed. This invention utilizes the optical signal output characteristics of mechanoluminescent materials to establish a real-time feedback control mechanism for the polishing process: the intensity of 480nm wavelength light emitted by the Bi-CaZnOS material is monitored in real time using a fiber optic spectrometer. This signal directly reflects the stress distribution and chemical reaction state in the polishing contact area. When the light intensity is lower than a set threshold, it indicates insufficient mechanical stress, and the system automatically increases the polishing pressure. When the light intensity is higher than the threshold, the pressure is appropriately reduced to prevent over-polishing. This intelligent pressure regulation strategy ensures that the polishing process is always in optimal working condition, significantly improving the stability, consistency, and repeatability of the process.

[0041] 6. Avoids the chemical pollution risks of traditional processes. This invention uses TiO2 photocatalyst to replace traditional strong oxidants such as potassium permanganate and high-concentration H2O2, fundamentally avoiding heavy metal pollution and metal contamination problems. The photocatalytic oxidation of TiO2 is a surface reaction carried out under mild conditions, which does not introduce new pollutants. The generated active oxygen species have short lifetimes and directional effects, preventing excessive corrosion of the SiC surface. In addition, Li⁺ doping reduces oxygen vacancy defects in the material lattice, and the piezoelectric field accelerates the dissolution and removal of reaction products (mainly SiOx), effectively preventing the accumulation of oxide layers. This significantly reduces the surface scratch density from 10.5 scratches / cm² in traditional methods to 1.8 scratches / cm², and the surface roughness Ra is as low as 0.42 nm.

[0042] 7. Broad Application Prospects. The mechanoluminescence-photocatalysis coupling mechanism established in this invention is not only applicable to the efficient polishing of SiC chips, but can also be extended to the precision processing of other third-generation semiconductor materials such as GaN, sapphire, and diamond, as well as the ultra-precision polishing of precision optical components. Furthermore, this technology has potential application value in environmental protection fields such as water treatment and air purification, providing a new technical path for mechanically driven photocatalytic reactions. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0044] Example 1: Preparation of Bi-CaZnOS Mecoluminescent Material

[0045] CaCO3, ZnS, Bi2O3, and Li2CO3 were prepared in a molar ratio of 0.95:1:0.05:0.10. Each component was accurately weighed (to four decimal places). The weighed raw materials were placed in an agate mortar, and 10 mL of anhydrous ethanol was added for dispersion. The mixture was ground for 30 minutes to ensure a more uniform mixture. The homogeneous precursor was then dried at 80°C for 4 hours and placed into crucibles, arranged starting from the gas inlet of a high-temperature tube furnace. The sample was then carefully placed into the high-temperature tube furnace and sealed. Nitrogen gas was introduced into the furnace tube at a rate of 0.1 L / min for approximately 15 minutes to ensure the air inside the furnace tube was purged. Following the pre-programmed procedure, the sample was sintered at 990°C for 3 hours under a nitrogen atmosphere. After the experiment, the sample was allowed to cool naturally to room temperature. The sample was then removed and thoroughly ground for approximately 15 minutes to obtain the Bi-CaZnOS metronome luminescent material.

[0046] In this preparation process, the introduction of Li⁺ plays multiple key roles: Firstly, after Li⁺ (ionic radius 0.76 Å) enters the CaZnOS lattice, it can occupy Ca²⁺ (ionic radius 1.00 Å) sites. Due to the valence difference between Li⁺ and Ca²⁺, a positively charged defect (Li·Ca) is generated. This defect forms a charge compensation relationship with the positively charged defect (Bi···Ca) generated by Bi³⁺ doping, effectively reducing the lattice distortion energy. Secondly, the introduction of Li⁺ reduces the concentration of oxygen vacancies (VO··) in the lattice, suppresses nonradiative recombination processes, and improves the luminescence quantum efficiency. In addition, Li⁺ doping optimizes the piezoelectric constant of the material and enhances its response sensitivity to mechanical stress. Compared with the traditional high-temperature process (1200℃), the low-temperature sintering process (990℃) of this invention not only reduces energy consumption by about 50%, but also significantly reduces the emission of toxic gases such as H₂S, achieving green and low-carbon manufacturing.

[0047] Example 2: Preparation of a chemical mechanical polishing slurry based on a Bi-CaZnOS mechanoluminescent catalyst

[0048] Take 1.25g of the Bi-CaZnOS mechanoluminescent material prepared in Example 1, 0.5g of N-type TiO2 photocatalyst (average particle size of about 20nm, purchased from Nanjing Advanced Materials Technology Co., Ltd., product model NT-01), mix them, add 50mL of deionized water, and ultrasonically disperse for 30 minutes. Then add 0.25g of Al2O3 abrasive with a particle size of 0.5μm (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product purity 99.9%), continue ultrasonic dispersion for 20 minutes, and finally add 0.1g of sodium carboxymethyl cellulose (CMC-Na) as a dispersion stabilizer, stir evenly, and obtain a chemical mechanical polishing slurry.

[0049] The TiO2 photocatalyst used in this embodiment is anatase N-type doped TiO2, which is one of the most extensively researched and widely used photocatalyst materials globally. Anatase TiO2 has a band gap of 3.2 eV, corresponding to an absorption edge of approximately 388 nm, and can be effectively excited by ultraviolet light with wavelengths less than 388 nm or even shorter wavelengths. However, the 480-500 nm blue-green light generated by the Bi-CaZnOS mechanoluminescent material of this invention has a sufficiently high photon flux density. Even in close contact with TiO2 nanoparticles, it can still effectively excite the photocatalytic activity of TiO2 through mechanisms such as thermally assisted light absorption and defect state absorption. More importantly, the penetration depth of 480-500 nm blue-green light in aqueous polishing fluid is much greater than that of ultraviolet light, which can activate dispersed TiO2 particles over a wider range, improving photocatalytic efficiency.

[0050] In this formulation, the mass ratio of Bi-CaZnOS mechanoluminescent material to TiO2 photocatalyst is 2.5:1. This ratio has been systematically optimized to achieve the best synergistic effect of mechanoluminescence and photocatalysis. During the CMP process, the Al2O3 abrasive provides both mechanical grinding and a stress source for the mechanoluminescent material, triggering the mechanoluminescence process. The generated 480-500nm blue-green light in situ excites the TiO2 photocatalyst, forming highly active oxide species, accelerating the oxidation of the SiC surface and promoting the removal of the oxide layer.

[0051] Example 3: Preparation of Bi-CaZnOS metronome materials with different Li⁺ doping amounts

[0052] Following the method of Example 1, three Bi-CaZnOS metronographic materials were prepared with CaCO3:ZnS:Bi2O3:Li2CO3 molar ratios of 0.95:1:0.05:0.05 (sample A), 0.95:1:0.05:0.10 (sample B), and 0.95:1:0.05:0.15 (sample C), respectively. Other preparation conditions were the same as in Example 1.

[0053] By adjusting the Li⁺ doping amount, the piezoelectric properties and luminescence characteristics of materials can be precisely tuned. Studies have found that an appropriate amount of Li⁺ doping (sample B, Li₂CO₃ molar ratio of 0.10) can minimize lattice defects, optimize the band structure, and improve luminescence efficiency, while excessive or insufficient doping leads to performance degradation. When the Li⁺ doping amount is too low (sample A), lattice vacancies and non-radiative recombination centers are difficult to fill effectively, limiting luminescence efficiency; when the Li⁺ doping amount is too high (sample C), excess Li⁺ ions may segregate at grain boundaries, forming a second phase, which introduces new defect states and affects carrier transport efficiency.

[0054] Example 4: Effect of different sintering temperatures on the properties of Bi-CaZnOS mesoluminescent materials

[0055] Following the method of Example 1, using the same raw material ratio (CaCO3:ZnS:Bi2O3:Li2CO3=0.95:1:0.05:0.10), three Bi-CaZnOS mechanoluminescent materials were prepared by sintering at 950℃ (sample D), 990℃ (sample E), and 1030℃ (sample F) for 3 hours.

[0056] Sintering temperature significantly affects the crystal structure and luminescence properties of materials. At low-temperature sintering (950℃), the solid-state reaction between raw materials is incomplete, resulting in insufficient crystallinity of the CaZnOS phase, numerous lattice defects, and low activation efficiency of Bi³⁺ luminescent centers. At high-temperature sintering (1030℃), although crystallinity increases, the diffusion coefficient of Bi³⁺ ions increases at high temperatures, making them prone to migration to grain boundaries or volatilization from the lattice, leading to a decrease in the actual doping rate. 990℃ is the optimized sintering temperature. At this temperature, the Li⁺-assisted doping strategy achieves its best effect, ensuring both sufficient solid-state reaction and good crystallization while maximizing the effective doping of Bi³⁺ luminescent centers, thus optimizing luminescence performance.

[0057] Example 5: Preparation of Bi-CaZnOS and TiO2 composite catalysts with different mass ratios

[0058] Following the method of Example 2, three composite catalysts with Bi-CaZnOS to TiO2 mass ratios of 1.5:1 (sample G), 2.5:1 (sample H), and 3.5:1 (sample I) were prepared respectively. Other conditions were the same as in Example 2.

[0059] The mass ratio of Bi-CaZnOS to TiO2 directly affects the synergistic effect of mechanoluminescence and photocatalysis. When the ratio is too low (1.5:1), the mechanoluminescent material is relatively insufficient, resulting in a limited number of blue-green photons generated, which cannot fully activate the photocatalytic reaction, and the overall catalytic efficiency of the system is limited by the light source intensity. When the ratio is too high (3.5:1), although the mechanoluminescence intensity increases, the insufficient TiO2 content limits the number of photogenerated carriers, also affecting the catalytic efficiency. Experiments show that a mass ratio of 2.5:1 achieves the optimal balance between mechanoluminescence intensity and photocatalyst content, obtaining the best synergistic catalytic performance.

[0060] Example 6: Catalytic Performance Verification Method

[0061] The catalytic efficiency of the catalyst was evaluated using a methylene blue degradation experiment. Methylene blue is a commonly used organic dye model pollutant with a characteristic absorption peak at 664 nm. Its concentration change can be accurately measured using a UV-Vis spectrophotometer, and it is widely used for evaluating photocatalytic activity. The specific steps are as follows:

[0062] (1) Add 40 mL of Al2O3 microspheres with a particle size of 0.5 mm to a ZrO2 container (100 mL) as a stress source;

[0063] (2) Add 50 mL of 10 mg / L methylene blue solution and 0.1 g of the catalyst to be tested (samples from Examples 2-5) to the ZrO2 container.

[0064] (3) Place the ZrO2 container in the ball mill, set the speed to 450 r / min, and run it for 30 minutes and 180 minutes respectively;

[0065] (4) Take out the reaction solution, centrifuge and separate it, and measure the absorbance of the supernatant at 664 nm. Calculate the concentration of methylene blue through the standard curve, and then calculate the degradation rate.

[0066] This method simulates the mechanical stress environment of the CMP process and evaluates the degradation efficiency of different catalysts under mechanoluminescence-photocatalysis synergy in the dark (without external light source). During ball milling, the collision and friction between Al2O3 microspheres and catalyst particles generate mechanical stress, which excites the luminescence of Bi-CaZnOS material, thereby activating the TiO2 photocatalytic reaction. This verification method provides a scientific and simple experimental basis for evaluating the catalytic performance of polishing slurries.

[0067] Example 7: SiC Chip Polishing Application Method

[0068] Polishing experiments on SiC chips were conducted using the chemical mechanical polishing slurry prepared in Example 2. The specific steps are as follows:

[0069] (1) The prepared polishing liquid was applied to a polyurethane polishing pad (IC1000, Rohm and Haas);

[0070] (2) Fix the 4H-SiC wafer (2 inches in diameter, (0001) Si surface, purchased from the 46th Research Institute of China Electronics Technology Group Corporation) onto the wafer tray of the polishing machine;

[0071] (3) Set the polishing pressure to 3 psi and the relative rotation speed to 60 rpm for polishing;

[0072] (4) At the same time, the intensity of the 480nm wavelength light emitted by the Bi-CaZnOS material was monitored in real time using a fiber optic spectrometer (Ocean Optics, QE65000);

[0073] (5) When fluctuations in light intensity signal are detected, adjust the polishing pressure accordingly: increase the pressure when the light intensity decreases and decrease the pressure when the light intensity is too high, so as to keep it in the optimal working range.

[0074] This self-feedback control mechanism enables real-time and precise control of the polishing process. The 480nm luminescence intensity directly reflects the stress state and chemical reaction process in the polishing contact area: too low luminescence intensity indicates insufficient mechanical stress and a limited chemical oxidation reaction rate; too high luminescence intensity indicates excessive stress, which may lead to surface damage. Based on this principle, the intelligent control strategy significantly improves the efficiency, consistency, and surface quality of SiC chip polishing.

[0075] Example 8: Effect of different polishing conditions on the surface quality of SiC chips

[0076] Based on the polishing slurry prepared in Example 2, SiC chips were polished using different polishing pressures (0.5psi, 3psi, and 5psi) and different polishing times (5 minutes, 15 minutes, and 30 minutes), with other conditions being the same as in Example 7.

[0077] After polishing, surface roughness was measured using atomic force microscopy (AFM, Bruker Dimension Icon), surface morphology was observed using scanning electron microscopy (SEM, JEOL JSM-7800F), and surface scratch density was calculated using optical microscopy. The results showed that optimal surface quality, with a surface roughness Ra < 0.5 nm and a scratch density < 2 scratches / cm², could be obtained with appropriate polishing pressure (3 psi) and polishing time (15 minutes). At low pressure (0.5 psi), the mechanical stress was insufficient to effectively excite mechanoluminescence, resulting in a low chemical reaction rate and limited material removal efficiency; at high pressure (5 psi), the risk of mechanical damage increased, and the surface scratch density rose.

[0078] Comparative Example 1: Bi-CaZnOS metronome material without Li⁺ doping

[0079] Following the method of Example 1, but without adding Li⁺-doped Bi-CaZnOS metronographic material (i.e., CaCO₃:ZnS:Bi₂O₃ = 0.95:1:0.05), other conditions were the same as in Example 1.

[0080] Undoped Li⁺ materials exhibit numerous lattice defects, particularly vacancies at Ca²⁺ sites and oxygen vacancies. These defects act as nonradiative recombination centers, severely impacting luminescence efficiency. Furthermore, the lack of Li⁺ charge compensation exacerbates the lattice distortion caused by Bi³⁺ doping, further reducing the material's piezoelectric properties and stress response sensitivity. Experimental results show that the mechanoluminescence efficiency of undoped Li⁺ materials is approximately 60% lower than that of Li⁺-assisted doped materials, fully validating the crucial role of the Li⁺-assisted doping strategy in this invention.

[0081] Comparative Example 2: Bi-CaZnOS Mecoluminescent Material Prepared by Conventional High Temperature

[0082] Bi-CaZnOS metronome material was prepared according to the formulation of Example 1, but using a conventional high-temperature sintering process of 1200°C for 2 hours. Other conditions were the same as in Example 1.

[0083] High-temperature sintering significantly increases the diffusion coefficient of Bi³⁺ ions. Some Bi³⁺ ions migrate to grain boundaries to form a Bi-rich phase, while others volatilize and are lost as Bi₂O₃ at high temperatures. Inductively coupled plasma mass spectrometry (ICP-MS) analysis showed that the actual Bi³⁺ doping rate in the 1200℃ sintered sample was only about 65% of the theoretical value, while the actual doping rate in the 990℃ sintered sample was over 90%. Furthermore, the rate of H₂S gas release from the decomposition of ZnS during high-temperature sintering significantly increases, raising environmental pollution risks and operational safety hazards.

[0084] Comparative Example 3: Polishing slurry containing only TiO2 photocatalyst

[0085] The polishing slurry was prepared according to the method of Example 2, but without adding Bi-CaZnOS mechanoluminescent material, using only 0.5 g TiO2 photocatalyst and 0.25 g Al2O3 abrasive. Other conditions were the same as in Example 2.

[0086] Polishing slurries lacking mechanoluminescent materials cannot effectively activate the photocatalytic activity of TiO2 without an external light source. Material removal relies solely on mechanical grinding and a small amount of intrinsic oxidation of TiO2. Experimental results show that the material removal rate of the TiO2-only polishing slurry in SiC polishing is only about 30% of that in Example 2, and the surface quality also decreases significantly. This fully demonstrates the core role of mechanoluminescent materials in the system of this invention—providing an in-situ light source to activate the photocatalytic reaction.

[0087] Comparative Example 4: Traditional polishing slurry containing only H2O2

[0088] A traditional polishing slurry was prepared using a traditional formula, with 5wt% H2O2 as an oxidant, 0.5g Al2O3 abrasive (particle size 0.5μm) and an appropriate amount of dispersant.

[0089] Traditional H2O2 polishing slurries achieve a material removal rate of only 95±8 nm / h in SiC polishing, far lower than the polishing slurry of this invention (287±12 nm / h). This is because H2O2 oxidation of the SiC surface is a diffusion-controlled, slow process, with the chemical reaction and mechanical removal occurring asynchronously, resulting in low efficiency. Furthermore, traditional polishing slurries exhibit a surface scratch density exceeding 10 scratches / cm², and high concentrations of H2O2 easily introduce metal contamination (such as Fe and Cu ions dissolved from reactors or pipelines), affecting chip performance and reliability.

[0090] Test Results and Analysis

[0091] Table 1: Comparison of mechanoluminescence intensity of Bi-CaZnOS materials with different Li⁺ doping concentrations

[0092] Sample number <![CDATA[Molar ratio of Li2CO3]]> Relative luminous intensity (au) Peak wavelength (nm) Sample A 0.05 156 485 Sample B 0.10 243 480 Sample C 0.15 197 478 Comparative Example 1 0 98 493

[0093] As shown in Table 1, Li⁺ auxiliary doping significantly optimizes the mechanoluminescence performance of Bi-CaZnOS materials. The undoped Comparative Example 1 sample exhibits the lowest luminescence intensity (98 au), with a peak wavelength at 493 nm. With increasing Li⁺ doping concentration, the luminescence intensity first increases and then decreases, reaching a maximum of 243 au at a Li₂CO₃ molar ratio of 0.10, approximately 2.5 times higher than the undoped sample. Simultaneously, Li⁺ doping causes a blue shift of the luminescence peak to around 480 nm, a wavelength closer to the effective absorption range of the TiO₂ photocatalyst, which is beneficial for improving light energy utilization efficiency. It is noteworthy that the 480 nm blue light emission achieved in this invention is extremely rare in the field of mechanoluminescent materials—the vast majority of mechanoluminescent materials emit light in the green, yellow, or even infrared regions. The scarcity of blue-emitting materials gives this invention unique technical value.

[0094] Table 2: Effect of different sintering temperatures on the properties of Bi-CaZnOS materials

[0095] Sample number Sintering temperature (°C) Relative luminous intensity (au) Bi³⁺ Actual Doping Rate (%) Sample D 950 187 82 Sample E 990 243 90 Sample F 1030 215 85 Comparative Example 2 1200 148 65

[0096] Table 2 shows the key effects of sintering temperature on material properties. 990℃ is the optimized sintering temperature, at which sample E exhibits the highest luminescence intensity (243 au) and actual Bi³⁺ doping rate (90%). Compared to the conventional 1200℃ high-temperature process, the low-temperature process of this invention not only improves the luminescence intensity by 64% and the Bi³⁺ doping rate by 38%, but also significantly reduces energy consumption and environmental pollution. The advantages of low-temperature sintering are attributed to the introduction of a Li⁺-assisted doping strategy. Li⁺ lowers the diffusion barrier for Bi³⁺ to enter the crystal lattice, allowing the solid-state reaction to be completed at a lower temperature, avoiding Bi³⁺ volatilization and lattice damage caused by high temperatures.

[0097] Table 3: Test Results of Catalytic Performance of Methylene Blue Degradation

[0098] Sample number Composition (mass ratio) 30-minute degradation rate (%) Degradation rate (%) at 180 minutes Sample G <![CDATA[Bi-CaZnOS:TiO2=1.5:1]]> 95.45 93.95 Sample H <![CDATA[Bi-CaZnOS:TiO2=2.5:1]]> 100.28 101.02 Sample I <![CDATA[Bi-CaZnOS:TiO2=3.5:1]]> 99.34 100.34 Comparative Example 3 <![CDATA[Only TiO2]]> 91.95 92.57 blank Catalyst-free 91.93 50.32

[0099] Table 3 shows the methylene blue degradation results, which strongly demonstrate the high catalytic efficiency of the mechanoluminescence-photocatalysis coupling system. Under dark conditions (no external light source), sample H with a Bi-CaZnOS:TiO2 ratio of 2.5:1 achieved a degradation rate of 100.28% within 30 minutes (the >100% result is due to normal fluctuations caused by experimental measurement errors), significantly higher than Comparative Example 3 (91.95%) and the blank control group containing only TiO2. This result clearly indicates that under mechanical stress, the blue-green light generated by the Bi-CaZnOS mechanoluminescent material can effectively activate the TiO2 photocatalyst, producing highly active oxide species and achieving efficient conversion of mechanical energy into chemical energy. The degradation rates of Comparative Example 3 and the blank group were similar at 30 minutes, indicating that the dark-state catalytic activity of TiO2 is limited without mechanoluminescence excitation; however, at 180 minutes, the degradation rate of the blank group significantly decreased to 50.32%, which may be related to the photodegradation equilibrium of methylene blue in the liquid phase.

[0100] Table 4: Comparison of polishing performance of SiC chips by different polishing slurries

[0101] Polishing fluid type Material removal rate (nm / h) Surface roughness Ra (nm) <![CDATA[Scratch density (number / cm 2 )]]> Example 2 287±12 0.42 1.8 Comparative Example 3 85±9 0.78 6.3 Comparative Example 4 95±8 0.86 10.5

[0102] Table 4 fully demonstrates the superior performance of this invention in SiC chip polishing applications. The polishing slurry based on the Bi-CaZnOS mesionic catalyst (Example 2) achieved a material removal rate of 287±12 nm / h, which is 3.4 times that of the TiO2-only polishing slurry (Comparative Example 3) and 3.0 times that of the traditional H2O2 polishing slurry (Comparative Example 4). Simultaneously, surface quality was significantly improved: surface roughness Ra decreased from 0.86 nm (Comparative Example 4) to 0.42 nm, and scratch density decreased from 10.5 scratches / cm² to 1.8 scratches / cm². This comprehensive improvement in performance indicators is attributed to the mesionic-photocatalytic coupling mechanism: on the one hand, the in-situ generated highly active oxide species accelerate the chemical oxidation process on the SiC surface; on the other hand, the reduced lattice oxygen vacancies due to Li⁺ doping and the product dissolution accelerated by the piezoelectric field effectively prevent oxide layer accumulation and mechanical scratches.

[0103] Based on the above embodiments and test results, the optimal implementation scheme of the present invention is as follows:

[0104] Preparation of Bi-CaZnOS mechanoluminescent material: The molar ratio of CaCO3:ZnS:Bi2O3:Li2CO3 was 0.95:1:0.05:0.10, and the material was sintered at 990℃ for 3 hours under a nitrogen protective atmosphere.

[0105] The chemical mechanical polishing slurry is composed of Bi-CaZnOS mechanoluminescent material and TiO2 photocatalyst in a mass ratio of 2.5:1, with Al2O3 abrasive with a particle size of 0.5μm added as a stress source and polishing medium.

[0106] SiC chip polishing conditions: polishing pressure 3psi, relative rotation speed 60rpm, real-time monitoring of 480nm luminescence intensity and dynamic adjustment of polishing pressure.

[0107] Under this optimal implementation, the material removal rate of the SiC chip can reach 287±12nm / h, the surface roughness Ra is as low as 0.42nm, and the scratch density is only 1.8 scratches / cm², achieving efficient and high-quality SiC chip polishing.

[0108] The core innovation of this invention lies in establishing a mechanoluminescence-photocatalysis coupling mechanism, achieving a highly efficient closed-loop conversion of mechanical energy → light energy → chemical energy. This innovative energy conversion path is fundamentally different from traditional polishing techniques, and its working mechanism can be elaborated in detail from the following aspects:

[0109] First layer: Mechanism-electric coupling (mechanical energy → electrical energy). During CMP, the contact friction between the abrasive (Al2O3 or SiO2) and the SiC surface generates localized mechanical stress. This stress is transferred to the dispersed Bi-CaZnOS mechanoluminescent particles through the polishing slurry. Because Li⁺-assisted Bi³⁺ doping optimizes the CaZnOS lattice structure, the material exhibits a significant piezoelectric effect. Under stress, the lattice undergoes asymmetric deformation, and the relative displacement of positive and negative ions leads to the generation of polarized charges within the crystal, forming a polarization charge with an intensity exceeding 10. 6 A piezoelectric field of V / m. This piezoelectric field is the trigger source for the subsequent light emission process.

[0110] The second layer: Electro-optical conversion mechanism (electrical energy → light energy). A piezoelectric field drives the separation and directional migration of charge carriers (electrons and holes) within the crystal lattice. Excited-state electrons interact with the 6s²6p¹ electron orbitals of the Bi³⁺ luminescent center, causing Bi³⁺ to transition from the ground state (¹S0) to the excited state (³P1). Subsequently, the excited-state Bi³⁺ returns to the ground state via radiative transition, releasing blue-green photons with a wavelength of 480-500 nm. It is worth emphasizing that 480 nm blue light emission is extremely rare in the mechanoluminescent material family; this unique luminescent characteristic is the physical basis for achieving efficient photocatalytic coupling in this invention.

[0111] The third layer: photo-chemical coupling mechanism (light energy → chemical energy). This invention cleverly utilizes the bandgap matching relationship between the emission spectrum of Bi-CaZnOS and the absorption spectrum of TiO2. The bandgap of commercial anatase TiO2 is 3.2 eV (corresponding to an absorption edge of approximately 388 nm), theoretically requiring ultraviolet light for effective excitation. However, this invention achieves effective activation of TiO2 by blue-green light (480-500 nm, approximately 2.5-2.6 eV) through the following pathways: First, N-type doped TiO2 introduces shallow defect states in the bandgap, reducing the effective excitation energy; second, the mechanoluminescent material and TiO2 nanoparticles are dispersed at close range in the polishing solution, and the high photon flux density compensates for the insufficient single-photon energy; third, the local temperature rise generated by the CMP process provides the conditions for thermally assisted light absorption. Under blue-green light excitation, TiO2 valence band electrons transition to the conduction band, forming photogenerated electron-hole pairs, which then react with adsorbed O2 and H2O to generate highly reactive oxidizing species such as superoxide anions (·O2⁻) and hydroxyl radicals (·OH).

[0112] The fourth layer: Chemical reaction acceleration mechanism. The reactive oxygen species generated by photocatalysis possess extremely high oxidation potentials, enabling them to directionally attack the Si-C bonds on the SiC surface (bond energy approximately 435 kJ / mol), oxidizing them to SiOx and CO2. Compared to traditional H2O2 oxidants, photocatalytic reactive oxygen species exhibit faster reaction rates and higher selectivity, and the reaction occurs within a micro-region closely adhering to the SiC surface, achieving spatiotemporal synchronization of chemical oxidation and mechanical removal. More importantly, Li⁺ doping reduces the oxygen vacancy concentration in the Bi-CaZnOS lattice, and the piezoelectric field accelerates the dissolution and removal of reaction products (mainly SiOx), effectively preventing oxide layer accumulation and ensuring a continuous and efficient material removal process.

[0113] Synergistic Mechanism of Technical Features: There is a close synergistic relationship among the various technical features of this invention. The Li⁺-assisted doping strategy simultaneously optimizes the material's luminescence properties (reducing non-radiative recombination) and piezoelectric properties (enhancing stress response), both working together in the mechanoluminescence process. The 480-500nm blue light emission band matches the absorption characteristics of TiO₂, achieving efficient light energy transfer. The low-temperature sintering process ensures efficient Bi³⁺ doping, and a high doping rate is a prerequisite for achieving high luminescence intensity. The self-feedback control system regulates the polishing pressure based on the luminescence signal, which itself depends on the material's mechanoluminescence properties. These technical features are interconnected, forming a complete technical system, none of which can be omitted.

[0114] The differentiating mechanism compared to existing technologies: Compared to traditional CMP technologies driven by oxidants (such as H2O2 and KMnO4), the essential difference of this invention lies in the different energy conversion pathways. Traditional technologies rely on the self-oxidizing ability of chemical reagents, which is a "matter-driven" reaction mode; this invention, however, converts mechanical energy into chemical energy through force-light-chemistry multi-field coupling, which is an "energy-driven" reaction mode. The advantages brought by this mode shift include: in-situ generation of reactive species, controllable concentration (by adjusting luminescence intensity through pressure), no risk of metal ion introduction, and the ability to achieve intelligent feedback control. Compared to photocatalytically assisted CMP with an external ultraviolet light source, the mechanoluminescent material of this invention generates light in-situ in the polished contact area, resulting in higher light energy utilization efficiency and eliminating the need for complex optical path design and equipment modification.

[0115] This invention is not only applicable to the efficient polishing of SiC chips, but can also be extended to the following fields:

[0116] Precision polishing of other third-generation semiconductor materials (such as GaN, sapphire, diamond, etc.) provides key process support for the manufacturing of high-frequency, high-power electronic devices.

[0117] Precision optical component processing, such as surface treatment of high-precision optical lenses and prisms, improves the surface quality and optical performance of optical components.

[0118] Mechanoluminescence-photocatalysis coupling systems can be applied to environmental protection fields such as water treatment and air purification, using mechanical energy to drive the degradation of pollutants and achieve efficient energy utilization.

[0119] The principle of this technology can be further extended to fields such as piezoelectric energy harvesting and self-driven sensors, providing technical support for new energy conversion and intelligent sensing systems.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A chemimechanical polishing slurry based on a Bi-CaZnOS mechanoluminescent catalyst, characterized in that, The polishing slurry includes Bi-CaZnOS mechanoluminescent material, TiO2 photocatalyst and dispersion medium, wherein the mass ratio of Bi-CaZnOS mechanoluminescent material to TiO2 photocatalyst is 1.5-3.5:

1.

2. The chemical mechanical polishing slurry according to claim 1, characterized in that, The mass ratio of the Bi-CaZnOS mechanoluminescent material to the TiO2 photocatalyst is 2.5:

1.

3. The chemical mechanical polishing slurry according to claim 1, characterized in that, The polishing fluid also includes Al2O3 or SiO2 abrasive, the particle size of which is 0.1-1.0 μm.

4. The chemical mechanical polishing slurry according to claim 1, characterized in that, The Bi-CaZnOS metronome material was prepared by the following method: (1) Mix the raw materials according to the molar ratio of CaCO3:ZnS:Bi2O3:Li2CO3=0.9-1.0:1:0.03-0.07:0.05-0.15; (2) Add anhydrous ethanol and grind and disperse to form a uniformly mixed precursor; (3) Dry the precursor at 80-100℃; (4) Under a nitrogen protective atmosphere, the dried precursor is sintered at 900-1050℃ for 2-4 hours; (5) After the material is naturally cooled to room temperature in the furnace, it is taken out and ground to obtain the Bi-CaZnOS mechanoluminescent material.

5. The chemical mechanical polishing slurry according to claim 4, characterized in that, The molar ratio of CaCO3:ZnS:Bi2O3:Li2CO3 is 0.95:1:0.05:0.

10.

6. The chemical mechanical polishing slurry according to claim 4, characterized in that, In step (2), the grinding and dispersion time is 30-60 minutes; in step (3), the drying time is 3-5 hours; in step (4), the sintering temperature is 990℃ and the sintering time is 3 hours; in step (5), the grinding time is 15-30 minutes.

7. The method for verifying the catalytic performance of the chemical mechanical polishing slurry according to any one of claims 1-6, characterized in that, The verification method includes the following steps: (1) First, Al2O3 or SiO2 small balls are placed in the ball mill as stress sources; (2) Next, add methylene blue solution and the catalyst to be tested to the ball mill; (3) Then, start the ball mill and run it at the predetermined speed for the predetermined time; (4) Finally, the degradation rate of methylene blue was measured to evaluate the catalytic efficiency of the catalyst.

8. The catalytic performance verification method according to claim 7, characterized in that, The ball mill rotates at a speed of 400-500 r / min, the initial concentration of the methylene blue solution is 5-20 mg / L, and the predetermined time is 30-180 minutes.

9. The method of applying the chemical mechanical polishing slurry according to any one of claims 1-6 in the polishing of SiC chips, characterized in that, The application method includes the following steps: (1) First, the chemical mechanical polishing slurry is applied to the polishing pad; (2) Next, the SiC chip is brought into contact with the polishing pad; (3) Then, pressure is applied to make the SiC chip move relative to the polishing pad; (4) At the same time, the intensity of the 480nm wavelength light emitted by the Bi-CaZnOS material is monitored in real time; (5) Finally, the polishing pressure is adjusted in real time based on the light intensity signal.

10. The application method according to claim 9, characterized in that, The polishing pressure is 0.5-5 psi, the relative motion speed is 30-120 rpm, and the polishing time is 5-30 minutes; wherein, when the intensity of the 480nm wavelength light is lower than a preset threshold, the polishing pressure is increased; when the intensity of the 480nm wavelength light is higher than the preset threshold, the polishing pressure is decreased.