Views: 222 Author: Lake Publish Time: 2025-03-26 Origin: Site
Content Menu
● Introduction to Silicon Carbide Polishing
● Polishing Methods for Silicon Carbide
>> 1. Ultrasonic-Assisted Chemical Mechanical Polishing (UACMP)
>> 2. Chemical Mechanical Polishing (CMP)
● Step-by-Step Polishing Process
>> 2. Polishing Fluid Preparation
>> 3. Polishing Equipment Setup
● Applications of Polished SiC
● FAQ
>> 1. What is the best polishing fluid for SiC?
>> 2. How to reduce scratches during polishing?
>> 3. Why is SiC polishing slower than silicon?
>> 4. How to handle thin SiC wafers without breakage?
>> 5. Can SiC be polished to optical-grade smoothness?
Silicon carbide (SiC) is a critical material in industries ranging from semiconductors to aerospace due to its exceptional hardness, thermal conductivity, and chemical resistance. However, its extreme properties make polishing challenging. This guide explores advanced techniques, tools, and best practices for achieving ultra-smooth SiC surfaces, supported by data, visuals, and practical insights.
Silicon carbide (Mohs hardness: 9.3) is harder than most materials, requiring specialized methods to achieve nanoscale surface roughness (<1 nm). Polishing aims to eliminate surface defects like scratches, pits, and subsurface damage while maintaining high material removal rates (MRR). Applications include:
- Semiconductors: SiC wafers for power electronics.
- Optics: High-precision mirrors and lenses.
- Industrial: Wear-resistant coatings and cutting tools.
Combines chemical etching and mechanical abrasion with ultrasonic vibration to enhance efficiency.
Key Components:
- Polishing Fluid: Triethylamine (3wt%), potassium hydrogen phthalate (1wt%), SiO₂/Al₂O₃ abrasives (5wt%), H₂O₂ (6wt%).
- Ultrasonic Parameters: 20 kHz frequency, 2 μm amplitude.
- Results: Ra reduced from 95 nm to 3 nm, MRR = 25.96 nm/min.
A standard method for semiconductor wafers, balancing chemical oxidation and mechanical removal.
Optimized Slurry:
- Oxidizers: H₂O₂, Fe(NO₃)₃.
- Abrasives: Colloidal silica (20–50 nm).
- pH: 10–12 (KOH or NH₄OH).
Challenges:
- Low MRR (~5 μm/hr vs. silicon's 100–200 μm/hr).
- High defectivity (scratches, particle residues).
Solutions:
- Diamond Conditioning Pads: Maintain pad asperity for consistent abrasion.
- Lapping: Use diamond slurry (30–60 μm) to achieve Ra <1 μm.
- Cleaning: Remove residues with deionized water and isopropyl alcohol.
- UACMP Example: Mix triethylamine (3%), potassium hydrogen phthalate (1%), SiO₂/Al₂O₃ (5%), H₂O₂ (6%).
- CMP Example: Colloidal silica (10%), H₂O₂ (5%), pH 11 (KOH).
- Pressure: 11.76 N (UACMP) or 3–5 psi (CMP).
- Speed: 200 rpm (UACMP) or 50–100 rpm (CMP).
- Temperature: 20–25°C.
- Time: 2 hours for UACMP; 4–8 hours for CMP.
- Monitoring: Laser confocal microscopy for Ra measurement.
- Megasonic Cleaning: Remove sub-100 nm particles.
- Drying: Nitrogen blow-off to prevent watermarks.
| Challenge | Solution |
|---|---|
| Low MRR | Optimize slurry oxidizers (H₂O₂, Fe⊃3;⁺). |
| Surface Defects | Use defect-reduced slurries and diamond conditioning. |
| Wafer Breakage | Handle wafers with vacuum chucks and edge protection. |
| High Cost | Recycle slurries and extend pad lifespan. |
- Devices: MOSFETs, Schottky diodes.
- Benefits: Higher efficiency in EVs and renewables.
- Use: Laser mirrors, aerospace windows.
- Specs: Ra <0.5 nm for high-reflectivity coatings.
- Examples: Cutting inserts, nozzles.
- Advantage: 10x longer lifespan than tungsten carbide.
1. Plasma-Assisted Polishing: Combines plasma etching with mechanical abrasion for Ra <0.1 nm.
2. AI-Driven Process Control: Machine learning optimizes MRR and defectivity in real time.
3. Eco-Friendly Slurries: Biodegradable additives reduce environmental impact.
Polishing silicon carbide demands a balance between chemical reactivity, mechanical force, and precision tooling. UACMP and optimized CMP slurries achieve Ra <3 nm, while diamond abrasives handle coarse material removal. Innovations in plasma and AI promise to overcome current limitations in MRR and cost. By leveraging these techniques, industries can unlock SiC's full potential in high-performance applications.
A mix of triethylamine (3%), potassium hydrogen phthalate (1%), SiO₂/Al₂O₃ (5%), and H₂O₂ (6%) achieves Ra 3 nm in UACMP.
Use colloidal silica slurries and diamond-conditioned pads to minimize abrasive agglomeration.
SiC's hardness (9.3 Mohs) and chemical inertness require stronger oxidizers and finer abrasives, reducing MRR.
Use vacuum chucks with edge protection and low-pressure polishing (<5 psi).
Yes. Plasma-assisted polishing achieves Ra <0.1 nm for laser optics.
[1] https://www.nature.com/articles/s41598-024-77598-x
[2] https://blog.entegris.com/not-your-average-wafer-solving-cmp-challenges-in-high-volume-sic-production
[3] https://global.kyocera.com/prdct/fc/industries/products/002.html
[4] https://pmc.ncbi.nlm.nih.gov/articles/PMC9611252/
[5] https://marklapedus.substack.com/p/cmp-challenges-seen-for-200mm-silicon
[6] https://www.acmr.com/sic-challenges/
[7] https://nxhuiheng.en.made-in-china.com/product/BjLQcwZTSlks/China-High-Hardness-Silicon-Carbide-for-Sandblasting-and-Polishing.html
[8] https://ceramics.onlinelibrary.wiley.com/doi/10.1002/ces2.10183
[9] https://greensiliconcarbide.com/product/green-silicon-carbide-polishing-powder/
[10] https://journals.sagepub.com/doi/full/10.1177/1687814017729090
