Case Study: Root Cause Analysis of Machining Micro-Cracks in Solid SiC Focus Rings for Dry Etching Equipment & Thermal Field Reconstruction in Vertical CVD Furnaces

SemixLab Technical Application & Engineering Case Study

1. Executive Summary / Key Data Snapshot

2. Customer Background & Pain Points of Traditional Approaches

2.1 Customer Background

The customer is a high-end component supplier focusing on semiconductor front-end dry etching equipment, long supplying critical consumables such as high-purity Solid SiC (pure silicon carbide) Focus Rings and Edge Rings to 12-inch wafer fabrication lines. Inside plasma etching chambers, Solid SiC components must withstand intense bombardment from high-power fluorine-based and chlorine-based plasma, demanding extremely stringent purity (>99.999%), density, and structural integrity.

2.2 Traditional Practices & Historical Pain Points

Prior to adopting SemixLab's technical upgrade, the customer utilized traditional horizontal CVD furnaces to deposit and manufacture Solid SiC ring blanks, suffering from severe operational paralysis:

· • Immediate Shattering During Rough Machining with Sky-High Scrap Rates: Solid SiC annular blanks produced by traditional horizontal furnaces experienced an instantaneous release of huge accumulated thermal stress upon entering the diamond tool roughing or grinding stage. This caused radial through-thickness cracking and catastrophic scrap rates.

· • Uncontrollable Delivery Cycles & Surging Production Costs: Due to frequent blank scrap and severe machining losses, the production cycle of Solid SiC rings was indefinitely extended, consumable costs soared, and urgent spare-part replacement demands from downstream wafer fabs could not be met.

3. Key Challenges & Failure Mechanism Analysis

3.1 Physical Failure Morphology

During initial diamond cutting or rough machining of Solid SiC ring blanks, visible deep micro-cracks frequently initiated along the outer edge or inner hole perimeter. These cracks rapidly propagated and tore along grain boundaries during subsequent machining, leading to the total destruction of the entire ring body.

3.2 Stress & Mechanism Investigation

To identify the root cause of cracking, the SemixLab technical team conducted CAE computer numerical simulations to model and investigate the flow field and temperature field of the legacy horizontal furnace:

· • Asymmetric Thermal Field & Flow Field Imbalance in Horizontal Furnaces: CAE simulations revealed significant top-to-bottom gravitational settling and front-to-back thermal gradients inside the horizontal furnace chamber. This caused uneven reaction gas deposition rates and resulted in asymmetric crystal growth morphology.

· • Thermal Tensile Stress Concentration During Crystal Growth: During prolonged high-temperature CVD deposition, substantial residual tensile stress accumulated inside the Solid SiC blanks due to anisotropic thermal expansion and cooling rate differentials. When surface skin layers were removed during machining, the stress equilibrium was disrupted, and local stress concentration directly triggered matrix cracking.

4. Solution: Equipment Reconstruction & Process Optimization

To address high internal stress and rough machining cracking in Solid SiC blanks, the SemixLab engineering team achieved a major technical breakthrough through a three-pronged approach: Equipment Upgrades + Simulation Reconstruction + Process Optimization.

5. Results & Quantified Benefits

After deploying the reconstructed Solid SiC ring blanks to the machining production line and customer validation, breakthrough quantified results were achieved:

· • Quantum Leap in Machining Yield: Machining roughing yield for Solid SiC blanks jumped from low feasibility with frequent cracking (<20%) to over 95%.

· • Superior Structural Integrity: Cracking issues during rough machining were completely resolved. Machined Solid SiC rings exhibit zero micro-cracks, zero edge chipping, and exceptional concentricity and tolerance control.

· • Successful Multi-Customer Line Qualification: The upgraded Solid SiC rings successfully passed production line verification on 12-inch dry etching equipment across multiple semiconductor clients, securing high-volume orders.

6. Production & Quality Control (SemixLab Manufacturing Assurance)

· 1. Precision Vertical Deposition: SemixLab utilizes the upgraded vertical CVD reaction furnace with fully automated control over deposition temperature and gas flow rates, ensuring highly isotropic internal structures in Solid SiC blanks.

· 2. Stress & Non-Destructive Testing: 100% non-destructive testing (NDT) and stress evaluation are performed after blanks are unloaded, ensuring no hidden internal micro-cracks advance to machining.

· 3. Ultra-Precision CNC Grinding: High-precision 5-axis CNC cutting with specialized diamond grinding heads ensures uniform wall thickness and precise dimensional tolerances.

· 4. Ultra-Pure Cleaning & Packaging: Processed through ultrapure water and acid cleaning for particle removal, followed by double-layer vacuum packaging in a cleanroom prior to shipment.

7. Frequently Asked Questions (FAQ) & Summary

Q1: Why are vertical furnaces superior to horizontal furnaces for producing low-stress Solid SiC ring blanks?

Answer: Ring-shaped components possess inherent axial symmetry. Vertical furnaces deliver highly symmetrical flow and thermal field distributions, eliminating top-to-bottom and front-to-back thermal gradients caused by gravity and gas settling in horizontal furnaces. This significantly reduces anisotropic internal stress developed during deposition.

Q2: What direct benefits does a >95% machining yield bring to customers?

Answer: A dramatic increase in machining yield significantly reduces raw material waste and cuts production cycle times by over 50%. This enables us to provide customers with cost-competitive, highly stable supplies of Solid SiC etching rings.

Summary & Conclusion

As a core consumable in plasma etching equipment, the manufacturing challenge of Solid SiC lies not only in its extreme material hardness, but also in internal stress control during blank deposition. By conducting in-depth simulation analysis of legacy horizontal furnace thermal/flow fields and successfully transitioning to highly symmetrical vertical furnaces, SemixLab has completely solved the industry-wide challenge of rough machining cracking in Solid SiC blanks. Boosting machining yield from under 20% to over 95%, SemixLab provides robust material assurance for the localized and reliable supply of semiconductor etching chamber components.