Wafer Height Profiling for Chuck Table Foreign Matter Detection
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Solution Overview
Problem
Existing cutting apparatuses struggle to efficiently detect and prevent damage from foreign matter on the holding surface of a chuck table, which can lead to reduced processing quality of silicon wafers.
Innovation Solution
A cutting apparatus equipped with a chuck table, height measurement unit, and controller that measures and analyzes height distribution and change rates of the workpiece to detect foreign matter on the holding surface, providing error notifications if foreign matter is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If foreign matter detection is performed using an imaging unit, then foreign matter on the holding surface can be detected, but small foreign matter may be missed and detection efficiency is insufficient
Solution Approach 1:
The patent replaces the optical imaging-based detection system with a height measurement system that uses mechanical or non-optical sensing methods. The height measurement unit measures the actual height of the workpiece at multiple points, and the control unit calculates height distribution and change rates to detect foreign matter. This substitution allows for more precise detection of small foreign matter that cannot be detected by imaging, while maintaining efficient automated operation.
Solution Approach 2:
The patent changes the detection parameter from optical imaging to height measurement. Instead of relying on visual detection of foreign matter, the system measures height variations of the workpiece surface. By calculating height distribution and change rates, the system can detect even tiny foreign matter through subtle height differences, significantly improving detection precision while maintaining productivity.
2Productivity
If the workpiece is held on the chuck table without foreign matter detection, then processing speed is maintained, but the workpiece may be damaged or processing quality reduced
Solution Approach 1:
The patent implements preliminary detection of foreign matter before the cutting process begins. The height measurement unit measures the workpiece height, and the control unit analyzes height distribution and change rates to detect foreign matter on the holding surface. If foreign matter is detected, the system notifies the operator before processing starts, preventing workpiece damage while maintaining efficient production flow through automated pre-checks.
3Measurement precision
If height measurement and analysis are performed to detect foreign matter, then detection accuracy is improved, but system complexity increases
Solution Approach 1:
The height measurement unit serves multiple functions: it measures workpiece height for positioning, detects foreign matter on the holding surface, and provides data for quality control. The control unit performs multiple calculations including height distribution analysis and change rate calculation from the same measurement data. This multi-functionality improves detection accuracy while minimizing additional system complexity by making existing components do multiple jobs.
Data Source
AI summary
A cutting method that measures heights of an outer periphery of a wafer, calculates height distribution data, and then calculates change rates of the heights of the outer periphery of the wafer. Based on results of a comparison between the height change rates and a threshold, the cutting method determines whether or not foreign matter exists on a back surface of the wafer (i.e., whether or not foreign matter exists on a holding surface of a chuck table). The existence of foreign matter on the holding surface can hence be detected appropriately. If foreign matter exists on the holding surface, a worker is notified, and the cutting operation is cancelled. Therefore, the cutting method can appropriately give notification to the worker that foreign matter is stuck on the holding surface, and can also appropriately avoid performing cutting processing with foreign matter stuck on the holding surface.