Silicon carbide, with its exceptional performance, has become a core material for electric vehicles and new energy power grids. However, its extremely high hardness and inherent wafer warpage make its chemical mechanical polishing (CMP) a manufacturing bottleneck in the industry. To achieve ultra-precision global planarization, traditional uniform pressure application alone can no longer meet requirements. The key lies in constructing a closed-loop technology system with multi-zone precision pressure control as the core execution unit, deeply integrated with surface figure measurement and intelligent decision-making.
Why Does Silicon Carbide CMP Require More Precise Pressure Control?
Imagine the CMP process as polishing an extremely expensive piece of hard jade. Traditional single-zone pressure control is like using a flat wooden board to apply uniform pressure. For silicon carbide—a material that is both extremely hard and prone to warpage—this approach reveals immediate drawbacks:
• Extreme Material Hardness: Silicon carbide has a Mohs hardness of 9.2. Non-uniform pressure directly causes surface scratches and wafer breakage, resulting in irreversible damage.
• Inherent Warpage: Silicon carbide epitaxial wafers inherently possess warpage, preventing perfect contact with the polishing pad. Traditional overall pressure application leads to insufficient pressure (under-polishing) in warped areas and excessive pressure (over-polishing) in well-contacted regions.
• Stringent Requirements: Power devices demand zero tolerance for surface defects. Any minor non-uniformity directly impacts device breakdown voltage and reliability.
Single-technology improvements can no longer address these systemic challenges; innovation is required at the process system level.
Multi-Zone Pressure Control: How to Achieve "Precise Targeting" Pressure Application?
The core concept of multi-zone pressure control technology can be likened to "precision massage"—instead of applying uniform force with the entire palm, it uses multiple independently controlled fingers to apply precisely appropriate pressure to different regions on the wafer's backside.
Its precision system mainly consists of three parts:
Multi-chamber air bladders or independent pressure chambers: The polishing head interior is divided into multiple independent ring-shaped or fan-shaped pressure chambers. Each chamber can independently inflate/deflate to apply different pressures.
High-precision pressure sensors and pneumatic control systems: Each pressure chamber connects to independent precision pressure regulating valves and sensors, monitoring and maintaining set pressure values in real-time.
Intelligent data processing center: Receives data from sensors and dynamically adjusts pressure output for each zone according to preset process recipes.
Through deep integration with surface figure measurement systems, multi-zone pressure control achieves a leap from "passive pressure application" to "active shape adjustment," becoming an indispensable execution component in the surface figure closed-loop control system.
Surface Figure Closed-Loop Control: A System Engineering of Multi-Technology Collaboration
Modern silicon carbide CMP surface figure control is a system engineering effort encompassing the following key components:
High-Precision Surface Figure Sensing System
• Online optical interferometers capture wafer 3D topography in real-time
• Precise identification of warped regions and thickness variations
Intelligent Decision-Making and Pressure Mapping
• Process models convert surface figure data into pressure commands
• Adaptive algorithms optimize pressure parameters for each region
Multi-Zone Precision Pressure Execution
• Multi-chamber polishing heads enable independent pressure regulation across zones
• Dynamic compensation for inherent wafer warpage and process fluctuations
This closed-loop system fully leverages the technical potential of multi-zone pressure control, upgrading it from an independent execution unit to the core component of an intelligent surface figure control system.
Core Technical Advantages: The Leap from "Uniform" to "Excellent"
This technology system delivers multiple advantages:
Significantly Improved Wafer Global Flatness: By compensating for inherent wafer warpage and uneven polishing pad wear, multi-zone pressure control achieves nearly consistent material removal from wafer center to edge, minimizing within-wafer non-uniformity.
Enhanced Material Removal Rate: While maintaining uniformity, more optimized process pressures can be applied overall without sacrificing efficiency due to edge over-polishing concerns, effectively boosting productivity.
Reduced Surface Defects: Uniform pressure distribution prevents micro-scratches, fragmentation, and sub-surface lattice damage caused by locally excessive pressure, providing a perfect "substrate" for subsequent epitaxial growth or device manufacturing.
Enhanced Process Window and Flexibility: When facing minor differences between silicon carbide substrates from different suppliers or batches, multi-zone pressure control offers wider process adjustment space. Stable polishing results can be achieved by fine-tuning zone pressures, improving production robustness.
Challenges and Future Outlook
Despite its clear advantages, multi-zone pressure control technology faces challenges in application:
High System Complexity: Multiple independent pneumatic circuits and sensing systems increase equipment costs and maintenance difficulty.
High Process Development Barriers: Determining optimal multi-zone pressure recipes requires deep process knowledge and extensive experimental data accumulation.
Wafer Backside Edge "Color Difference": Current technology cannot completely eliminate edge thickness variations caused by micro non-uniform pressure distribution—a key factor still limiting higher yields.
Real-Time Model Accuracy: Achieving truly effective real-time dynamic control depends on precise process models and rapid response algorithms, presenting extremely high technical barriers.
Siplus CMP Technology Practice: Breaking Core Challenges through Innovation
Siplus Semiconductor has built a complete CMP solution by deeply integrating multi-zone pressure control with surface figure measurement and intelligent decision-making:
• Multi-zone pressure control: Dynamically compensates for wafer warpage/density differences, eliminating edge roll-off and center over-polishing
• High-rigidity integrated spindle architecture: Designed for high-pressure conditions, ensuring precision retention and longevity under long-term harsh operation
• Process and consumables co-optimization: Collaborative development of equipment, process recipes, and consumables provides customers with immediately usable "optimal process windows"
Currently, Siplus's silicon carbide CMP equipment and solutions have been validated and applied at domestic leading substrate manufacturers, stably achieving high removal rates, nanometer-level global flatness, and extremely low surface defect rates.
Silicon carbide CMP surface figure control technology has evolved from single pressure control to a complete technical system encompassing precise measurement, multi-zone execution, and intelligent decision-making. As the core execution component, multi-zone pressure control achieves precise regulation of silicon carbide wafer surface topography through deep integration with surface figure measurement, endpoint detection, and other technologies.
In the future, with the deep application of artificial intelligence and industrial internet technologies, silicon carbide CMP surface figure control will develop toward greater intelligence and adaptability, providing solid manufacturing technology support for the widespread application of silicon carbide semiconductors in electric vehicles, rail transit, smart grids, and other fields.