Description
RDS – Residue Detection System
The Residue Detection System (RDS) by Graftek Imaging is an advanced, high-throughput automated inspection platform designed to detect residual metal and other defects on semiconductor wafers during the Chemical Mechanical Planarization (CMP) process. This cutting-edge system eliminates the inefficiencies and inaccuracies of manual visual inspection, delivering 100% inline inspection to ensure real-time, defect-free wafer processing in modern semiconductor fabrication environments.
Key Features and Capabilities:
1. Custom Imaging and Illumination System
- The RDS is equipped with a high-resolution 1600×1400 pixel camera paired with custom-designed optics and illumination. This system ensures full-wafer imaging (200mm wafers) from a fixed distance of 150mm, allowing for precise defect detection across various wafer sizes.
- Covered under our Patent US20140263981A1, whose protected lighting technology allows for enhanced contrast differentiation between residual metal particles and patterned surfaces by using multiple light sources positioned at different angles. The specialized lighting is critical for detecting both copper and tungsten residuals, which are often indistinguishable under normal lighting conditions.
2. Advanced Residue Detection Algorithms
- The RDS utilizes a 12-bit imaging system capable of distinguishing 4,096 grayscale levels, allowing for the detection of even the smallest defects. The system is specifically calibrated to handle different metal types (e.g., copper, tungsten) with adjustable thresholds based on known good and defect wafer sets.
- The Advanced Residue Detection (ARD) algorithm is a proprietary solution that recognizes disruptions in the wafer’s pattern without relying on a golden template. This advanced algorithm enables the RDS to detect both bright and dark defects, even those that match the intensity of the surrounding wafer pattern.
- The system processes images in real-time, with no need for prior teaching or product-specific information, ensuring immediate and reliable defect detection across different product types and technology nodes.
3. Full Wafer Coverage and Defect Localization
- Unlike traditional inspection systems that require pre-alignment or partial imaging, the RDS provides full-wafer coverage in a single scan. The system can autonomously locate the wafer’s notch and determine its orientation, allowing for defect localization relative to this fixed reference point.
- Detailed defect reports are generated for each wafer, providing data on defect size, location, intensity, and total number of spots. This data is integrated into the facility’s Statistical Process Control (SPC) systems, enabling continuous process improvement and failure analysis.
Process Integration and Tool Compatibility
1. Seamless CMP Tool Integration
- The RDS is designed to be fully integrated into existing CMP tools with minimal impact on throughput. With its compact form factor (12″x12″x12″) and robust I/O interfaces, the system communicates seamlessly with polisher control software via the SECS/GEM protocol. This allows for real-time process adjustments based on defect data, such as alarm, pause, or abort actions.
- The RDS can be mounted within the CMP tool’s robotic system, leveraging its 6-axis tool robot for precise wafer placement, illumination, and imaging.
2. Closed-Loop Inspection and Feedback
- The RDS system supports a fully automated closed-loop inspection process, providing immediate feedback to the CMP tool. This enables the polisher to make corrective actions in real-time, based on the type and severity of detected defects.
- The system logs all inspection data for each wafer, enabling traceability of defects down to individual lots, product types, and even specific tools (e.g., plater, carrier heads). This data is invaluable for FMEA (Failure Mode and Effects Analysis) and process optimization.
RDS for Advanced Process Control
1. Versatile Recipe Management
- The RDS supports a highly flexible recipe system, allowing users to create and manage custom inspection recipes based on product type, metal type, defect size, and brightness thresholds. These recipes can be updated and refined without requiring downtime, ensuring maximum inspection efficiency across diverse manufacturing needs.
- For most applications, the RDS can operate using a universal recipe, achieving up to 99% inspection efficiency, significantly reducing the need for product-specific recipe adjustments.
2. Enhanced Process Monitoring and Defect Detection
- In addition to residual metal detection, the RDS system can be configured to detect a variety of other wafer-related defects, including wafer breakage and component failures such as head gimbal bearing damage, slurry loss, and other consumable failures.
- The RDS system logs historical images of all wafers processed, enabling post-process analysis and documentation for tool maintenance or human-induced incidents.
Operational and Cost Benefits
1. Return on Investment (ROI) and Efficiency
- The RDS delivers a rapid ROI, typically within one year, due to its ability to significantly reduce wafer scrap and rework costs. For example, the RDS reduces scrap risks from 75+ wafers in copper CMP processes to fewer than 10 wafers per event, translating to cost savings of over $45,000 per incident.
- By eliminating human inspection variability, the RDS improves overall line yield and reduces production cycle times, enhancing labor force productivity and minimizing misprocessing.
2. Minimal Maintenance and High Uptime
- The RDS system is designed for 24/7 operation with minimal maintenance, featuring a long Mean Time Between Failures (MTBF) for its camera, lighting, and electronics. The system includes self-calibration and automated verification tools to ensure consistent performance over time.
- Graftek Imaging offers remote monitoring and troubleshooting capabilities, allowing for offsite reprocessing of images and system diagnostics, reducing downtime and enabling continuous process improvements.