A silicon wafer chemical mechanical polishing liquid based on ternary polymer synergistic effect
The silicon wafer chemical mechanical polishing slurry, which utilizes the synergistic effect of ternary polymers, solves problems such as abrasive agglomeration, scratches, and metal contamination, achieving efficient and environmentally friendly silicon wafer surface planarization and meeting the polishing requirements of highly integrated silicon wafers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-03-05
- Publication Date
- 2026-06-26
AI Technical Summary
Existing silicon wafer CMP polishing slurries have drawbacks such as abrasive agglomeration, easy edge collapse and surface scratches, high risk of metal contamination, poor synergy between chemical and mechanical effects, and environmental unfriendliness, making it difficult to meet the requirements for surface planarization of highly integrated silicon wafers.
A silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers is adopted. Through the combination of silica sol, polyethylene glycol, cellulose derivatives and sorbitol, shear thickening, chemical complexation, interface modification and abrasive stabilization effects are formed, ensuring that the polishing slurry can efficiently remove defects on the surface of silicon wafers while reducing metal pollution and environmental impact.
It achieves efficient and environmentally friendly silicon wafer surface polishing, significantly reducing surface defects and metal contamination, meeting the planarization requirements of highly integrated silicon wafers, and reducing post-processing costs and environmental burden.
Smart Images
Figure CN122278355A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor material processing technology, specifically relating to a chemical mechanical polishing slurry for precision processing of silicon wafers, and in particular a highly efficient and green chemical mechanical polishing slurry based on the synergistic effect of a ternary polymer of polyethylene glycol, cellulose derivatives and sorbitol. Background Technology
[0002] As integrated circuits rapidly advance towards higher integration, higher efficiency, and lower power consumption, atomic-level planarization requirements have been placed on the surface flatness of silicon wafers in semiconductor manufacturing. Chemical mechanical polishing (CMP), currently the only core technology capable of achieving global planarization of silicon wafer surfaces, is an indispensable core process in the entire integrated circuit manufacturing industry chain. Its core lies in the synergistic effect of the polishing slurry—"chemical oxidation to form a soft reactive layer + abrasive mechanical removal"—to achieve high-precision polishing. The chemical additive system directly determines the balance between chemical and mechanical actions, thus directly affecting the final performance of CMP. In existing CMP technologies, silicon wafer CMP polishing slurries mainly employ mono- or binary polymer additive systems, focusing on optimizing single functions such as silicon wafer surface lubrication and rheological control. Furthermore, current mainstream silicon wafer CMP polishing slurries often contain toxic and harmful substances such as fluorides and amines (e.g., TMAH), posing environmental and safety risks, and resulting in high costs for post-processing and wastewater treatment.
[0003] Therefore, developing a multi-system coupled polishing slurry system that can combine rheological regulation, chemical complexation, interface modification, abrasive stabilization and shear thickening effects is difficult to meet the stringent requirements of advanced processes, making high-performance and environmentally friendly polishing slurries with multiple synergistic mechanisms a technological bottleneck. Summary of the Invention
[0004] To address the problems existing in the prior art, the purpose of this invention is to solve the defects of existing silicon wafer CMP polishing slurries, such as easy abrasive agglomeration, easy edge collapse and surface scratches, high risk of metal contamination, poor synergy between chemical and mechanical effects, and environmental unfriendliness. This invention provides a silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers that can balance chemical corrosion and mechanical polishing, significantly reduce surface defects and metal contamination, and is environmentally friendly. Specifically, this is achieved through the following technical solutions: A silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers, the slurry being composed of the following components by weight percentage: Silica sol: 5-15 wt%, particle size 20-120 nm; Polyethylene glycol: 0-10 wt%, excluding 0 wt%, molecular weight 1000-6000; Cellulose derivatives: 0-0.5 wt%, excluding 0 wt%, viscosity 40-10000 mPa·s; Sorbitol: 0-0.5 wt%, excluding 0 wt%; Oxidizing agent: 0.5-1.5 wt%, including but not limited to hydrogen peroxide and K2S2O8; pH adjuster: 0.3-0.8 wt%, to maintain the pH value of the polishing solution at 9.5-11.0; Deionized water: Balance.
[0005] Furthermore, the silica sol is a nano-sized silica abrasive with a particle size of 20-60 nm, and the concentration of the silica sol is 10-13 wt%. Using nano-silica with a particle size range of 20-60 nm as the polishing slurry abrasive ensures high polishing efficiency while reducing scratches on the silicon wafer surface caused by large particles.
[0006] Furthermore, the polyethylene glycol is a polyethylene glycol macromolecular compound containing 6 hydroxyl groups, with a molecular weight of 2000-6000. Polyethylene glycol in this range can give the polishing slurry near-non-Newtonian fluid properties, producing a local shear thickening effect on the raised parts of the silicon wafer surface, which can achieve polishing effect more efficiently, with a concentration of 5-6 wt%.
[0007] Furthermore, the cellulose derivative is selected from at least one of hydroxyethyl cellulose and hydroxypropyl cellulose.
[0008] Furthermore, the hydroxyethyl cellulose has a viscosity of 40-200 mPa·s. Hydroxyethyl cellulose with this viscosity range can form a liquid film of suitable thickness on the silicon wafer surface to prevent scratches from strong mechanical action. Its three-dimensional network structure can effectively maintain the suspension of abrasive particles, while avoiding the difficulty of subsequent cleaning caused by excessive thickening. The concentration is 0.03-0.2 wt%. The hydroxypropyl cellulose has a viscosity of 70-150 mPa·s. Hydroxypropyl cellulose with a higher proportion of hydrophobic ether groups in this viscosity range forms a lubricating film on the silicon wafer surface with better lubrication, which is more conducive to obtaining a high-quality silicon wafer surface while ensuring polishing efficiency. The concentration is 0.02-0.2 wt%.
[0009] Furthermore, the concentration of sorbitol is 0.005-0.05 wt%.
[0010] Furthermore, the oxidant is hydrogen peroxide with a concentration of 0.8-1.3 wt%.
[0011] Furthermore, the pH adjuster can be any one of ammonia, potassium hydroxide, or tetramethylammonium hydroxide.
[0012] Furthermore, ammonia is used as the pH adjuster to maintain the pH value of the polishing solution at 9.5-10.5.
[0013] In this technical solution, deionized water serves as the base solvent, and silica sol acts as the abrasive, participating in both chemical etching and mechanical grinding. A pH adjuster regulates the pH of the polishing slurry, allowing the difficult-to-remove silicon wafer surface to oxidize at a suitable rate under the action of the oxidant, generating a relatively easier-to-remove oxide layer. PEG with a molecular weight of 1000-6000 is selected. Its long-chain terminal hydroxyl groups (-OH) can undergo hydrogen bonding cross-linking reactions with the hydroxyl groups (Si-OH) on the silicon wafer surface and the SiO2 abrasive surface, forming a dual adsorption effect (reaction formula: PEG-OH + Si-OH → PEG-O-Si + H2O), ensuring that PEG preferentially adsorbs on the raised areas of the silicon wafer and the abrasive surface. On one hand, the lubricating film formed by adsorption can isolate the abrasive from direct hard contact with the silicon substrate, significantly reducing scratches and subsurface damage; on the other hand, the steric hindrance effect of the long-chain PEG can inhibit the excessive dissolution of silicon oxide in the raised areas, forming a selective passivation film, providing core support for the global self-planarization of the silicon wafer. Meanwhile, PEG molecular chains can form hydrogen bonds with the polyhydroxyl groups of sorbitol, enhancing the stability of the composite system. The molecular chain length and cross-linking density directly affect the sensitivity of the subsequent shear thickening effect. The selected hydroxyethyl cellulose (HEC) or hydroxypropyl cellulose (HPC) has a large number of hydroxyl groups (-OH) in its long-chain molecules that can intertwine through intermolecular hydrogen bonds to form a three-dimensional network rheological framework. This network structure can precisely encapsulate SiO2 abrasive (20-50 nm), preventing rapid sedimentation of the nano-abrasives and extending the residence time of the abrasives on the silicon wafer surface, thus enhancing the uniformity of mechanical grinding. More importantly, the cellulose network structure provides a core carrier for the shear thickening effect. When the shear rate is increased under appropriate polishing pressure, the molecular chains of the network structure undergo orientation rearrangement, increasing the cross-linking point density with PEG and sorbitol. The viscosity of the polishing fluid system instantly increases, forming a "rigid lubrication-grinding composite layer," which not only prevents silicon wafer edge collapse but also improves the grinding efficiency of the abrasive. Among them, the preferred low-viscosity HEC (concentration of 0.03-0.2 wt%) and the preferred low-viscosity HPC (0.02-0.2 wt%) can balance rheological stability and shear thickening response speed, avoiding the clogging of polishing pad micropores caused by high viscosity and ensuring the circulation efficiency of polishing fluid. The sorbitol molecule contains 6 hydroxyl groups (2 primary hydroxyl groups and 4 secondary hydroxyl groups), which can achieve complementary synergy through multiple chemical reactions and intermolecular interactions. First, through the formation of hydrogen bonds between the hydroxyl groups and the hydroxyl groups of PEG and cellulose, it strengthens the adhesion and shear resistance of the composite lubricating film, ensuring structural stability of the lubricating film under the shear thickening effect. Second, as a highly efficient chelating agent, its primary and secondary hydroxyl groups can react with Si released during silicon wafer polishing. 4+ and Fe introduced from the environment 3+ Cu2+ When metal ions undergo chelation reactions, stable five- or six-membered chelates are formed (with Cu as the base metal). 2+ For example, the reaction formula is: C6H 14 O6+ Cu 2+ → [Cu(C6H 12 O6)] 2+ + 2H + It can effectively prevent metal ions from reacting with OH groups. - The combination forms hydroxide precipitates (such as Cu(OH)2, Fe(OH)3), fundamentally preventing metal contamination and particle defects on the silicon wafer surface; thirdly, it forms hydrogen bonds with the silicon wafer surface oxide layer (SiO2) through hydroxyl groups (reaction formula: C6H). 14 O6+ SiO2→ C6H 12 O6-O-Si-O + H2O) gently promotes the softening of the oxide layer, improves wettability, and allows the high-viscosity polymer system to be evenly spread on the surface of the silicon wafer and polishing pad, avoiding surface distortion caused by insufficient or excessive polishing in certain areas.
[0014] Furthermore, the ternary system composed of cellulose derivatives, polyethylene glycol, and sorbitol involved in this invention possesses both excellent green and environmentally friendly properties and outstanding economic feasibility. Cellulose derivatives are renewable biomass materials with a biodegradability rate exceeding 95%. Their production process requires no toxic catalysts, and the degradation products are carbon dioxide and water, leaving no harmful residues. Polyethylene glycol (PEG 1000-6000) is a low-toxicity, inert polymer, non-irritating, and poses no teratogenic or carcinogenic risks. Its molecular structure is stable, and it does not release volatile organic compounds (VOCs) during polishing. It is completely degraded in the natural environment without the need for additional degradation agents to treat wastewater. Sorbitol, as a natural polyol, is widely found in fruit and plant juices. It can be prepared via glucose hydrogenation catalysis, resulting in a green and clean production process with no toxic byproducts and a biodegradability rate approaching 100%. The metal chelates formed by its chelation are easily decomposed and removed by subsequent SC1 cleaning solution, leaving no residue on the silicon wafer surface and preventing heavy metal accumulation pollution in aquatic environments. This completely eliminates the toxicity and corrosive risks associated with traditional fluorinated complexing agents (such as ammonium fluoroborate). The polishing slurry formulation involved in this invention can achieve efficient cross-linking without special pretreatment processes. The preparation process only requires conventional stirring and ultrasonic equipment, and is fully compatible with existing polishing slurry production lines. No additional equipment modification investment is required, which can significantly reduce the cost of industrialization transformation, provide core support for industrialization promotion, and have strong market competitiveness.
[0015] The polishing slurry of this invention achieves multi-coupling optimization such as abrasive stabilization, shear thickening, and chemical complexation through the precise ratio and synergistic effect of the ternary system. While ensuring a high material removal rate, it significantly reduces surface defects and metal contamination, meeting the surface polishing requirements of advanced process silicon wafers. Moreover, the polishing slurry formula is green and environmentally friendly, consisting of water-soluble polymers or biodegradable materials, which greatly reduces the environmental burden and simplifies post-processing procedures, making it easy to promote industrialization. Attached Figure Description
[0016] Figure 1 Optical microscope image of the silicon wafer before CMP; Figure 2 An optical microscope image of a silicon wafer after CMP using the polishing solution of Example 1 of this invention; Figure 3 An optical microscope image of a silicon wafer after CMP using the polishing solution of Example 2 of this invention; Figure 4 This is a scanning electron microscope image of the silicon wafer before CMP (Continuous Electron Microscopy). Figure 5 A scanning electron microscope image of a silicon wafer after CMP using the polishing solution of Example 1 of the present invention; Figure 6 This is a scanning electron microscope image of a silicon wafer after CMP using the polishing solution of Example 2 of the present invention. Detailed Implementation
[0017] The present invention will be further described below with reference to specific embodiments and accompanying drawings in order to better understand the technical solution.
[0018] Examples 1-2: Polishing fluid formulation Two polishing solutions (Example 1 and Example 2) were prepared according to the components and contents shown in Table 1. All components were mixed and stirred until homogeneous. The polishing solution formulations for Example 1 and Example 2 are shown in Table 1.
[0019] Table 1: Polishing Fluid Formulation
[0020] Verification example: Polishing experiment Polishing experiments were conducted on a CMP polisher, with parameters shown in Table 2. A 5×5 cm silicon wafer was fixed to a tray with paraffin wax, and CMP was performed for 1 min according to the experimental parameters shown in Table 2. 100 mL of deionized water and 0.5 mL of ammonia were added to beaker A. 100 mL of ammonia was added to beaker B. 100 mL of ethanol was added to beaker C. After polishing, the silicon wafer was removed and ultrasonically cleaned sequentially in beakers A, B, and C for 15–30 min. After cleaning, the silicon wafer was dried until no liquid residue remained on the surface, and then the surface morphology was verified using optical microscopy and scanning electron microscopy (SEM).
[0021] Table 2: Polishing Experiment Parameters
[0022] Experimental Results and Analysis: like Figure 1 and Figure 4 As shown, the silicon wafer surface before CMP was extremely rough, with numerous scratches of varying depths, and some particles and stains remaining. After CMP using the polishing slurry of Example 1, the surface... Figure 2 As can be seen from the optical microscope images, the surface quality of the silicon wafer was significantly improved, and the number of scratches was significantly reduced. Similarly, after CMP using the polishing slurry of Example 2, the surface quality of the silicon wafer was significantly improved. Figure 3 As shown in the optical microscope images, the surface quality of the silicon wafer was further improved compared to before polishing. This is because, under suitable pH conditions, the oxidant in the polishing slurry forms a more easily removable oxide layer on the silicon wafer surface. Subsequently, as the polishing slurry flows between the polishing pad and the silicon wafer, the increased shear rate creates a shear thickening effect, forming a flexible "flowing abrasive tool" that can more effectively remove uneven protrusions on the silicon wafer surface. Simultaneously, the cellulose and sorbitol in the polishing slurry system effectively prevent severe abrasive aggregation and form a lubricating layer on the silicon wafer surface that reduces over-grinding, ultimately resulting in a silicon wafer with significantly improved surface quality. Figure 5 , Figure 6 As can be seen from the scanning electron microscope images, microscopic defects (such as pits and protrusions) on the surface of the silicon wafer have been effectively removed, resulting in a high-quality, high-flatness surface.
[0023] Experimental results show that the ternary polymer synergistic polishing slurry provided by this invention, under alkaline conditions, enables the oxidant to form a soft oxide layer on the silicon wafer surface. Simultaneously, the PEG-induced shear thickening effect creates a "flexible abrasive" in the raised areas of the silicon wafer, enhancing the selectivity and efficiency of mechanical removal. The three-dimensional network structure of the cellulose derivative stabilizes the abrasive, preventing agglomeration, and together with PEG and sorbitol, constructs a robust lubricating film, effectively protecting the silicon wafer surface and preventing excessive wear and scratches. Sorbitol chelates metal ions in the system, preventing secondary contamination. It is this synergistic effect of the three components that achieves a perfect balance between chemical and mechanical action, resulting in excellent polishing performance.
Claims
1. A chemical mechanical polishing slurry for silicon wafers based on the synergistic effect of ternary polymers, characterized in that, The polishing slurry consists of the following components by weight percentage: Silica sol: 5-15 wt%, particle size 20-120 nm; Polyethylene glycol: 0-10 wt%, excluding 0 wt%, molecular weight 1000-6000; Cellulose derivatives: 0-0.5 wt%, excluding 0 wt%, viscosity 40-10000 mPa·s; Sorbitol: 0-0.5 wt%, excluding 0 wt%; Oxidizing agent: 0.5-1.5 wt%, including but not limited to hydrogen peroxide and K2S2O8; pH adjuster: 0.3-0.8 wt%, to maintain the pH value of the polishing solution at 9.5-11.0; Deionized water: Balance.
2. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The silica sol is a nano-sized silica abrasive with a particle size of 20-60 nm and a concentration of 10-13 wt%.
3. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The polyethylene glycol is a polyethylene glycol macromolecular compound containing 6 hydroxyl groups, with a molecular weight of 2000-6000 and a concentration of 5-6 wt%.
4. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The cellulose derivative is selected from at least one of hydroxyethyl cellulose and hydroxypropyl cellulose.
5. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 4, characterized in that, The hydroxyethyl cellulose has a viscosity of 40-200 mPa·s and a concentration of 0.03-0.2 wt%; the hydroxypropyl cellulose has a viscosity of 70-150 mPa·s and a concentration of 0.02-0.2 wt%.
6. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The concentration of sorbitol is 0.005-0.05 wt%.
7. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The oxidant is hydrogen peroxide, with a concentration of 0.8-1.3 wt%.
8. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 1, characterized in that, The pH adjuster can be any one of ammonia, potassium hydroxide, or tetramethylammonium hydroxide.
9. The silicon wafer chemical mechanical polishing slurry based on the synergistic effect of ternary polymers as described in claim 8, characterized in that, Ammonia is used as the pH adjuster to maintain the pH value of the polishing solution between 9.5 and 10.5.