Laser Scanning Defect Inspection System with Adaptive Control
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Solution Overview
Problem
Existing laser scattering defect inspection systems face challenges with poor positional precision of detected defect coordinates, leading to inefficiencies in defect location and increased inspection time, particularly during the LSI process and final shipment inspections.
Innovation Solution
A laser scattering defect inspection system that includes a stage unit for rotating and transporting the workpiece, a laser light source, an optical deflector for high-speed scanning using an acousto-optical deflector, and a control unit that adjusts scan conditions such as rotation speed, moving speed, scan width, and frequency to optimize defect inspection for each step, allowing for efficient detection of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a complex scanning method combining spiral scan and cross scan is used, then the beam spot size can be increased substantially and the wafer surface can be scanned effectively with fewer revolutions per minute, but the positional precision of the detected defect coordinates becomes poor
Solution Approach 1:
The patent applies dynamics by making the scanning parameters adaptive rather than fixed. The system dynamically adjusts the scanning method based on the inspection step: using complex scanning (spiral + cross scan) for final shipment inspection where speed is prioritized, and simple spiral scanning for LSI process inspection where positional precision is critical. This dynamic adaptation resolves the contradiction by allowing the system to optimize for either productivity or measurement precision depending on the specific application context.
Solution Approach 2:
The patent changes the scanning parameters (scan pattern, beam spot size, rotation speed) based on the inspection step requirements. For final shipment inspection, it uses larger beam spot size and complex scanning to improve productivity. For LSI process inspection, it uses smaller beam spot size and simple spiral scanning to maintain positional precision. This parameter adaptation allows the system to resolve the technical contradiction by matching scanning parameters to the specific inspection objectives.
2Speed
If the beam spot size is increased substantially using optical deflector, then the wafer surface can be scanned effectively with fewer revolutions per minute, but the inspection time per wafer increases for total inspection applications
Solution Approach 1:
The system dynamically adjusts the rotation speed and scanning method based on the inspection step. For final shipment inspection, it uses higher rotation speeds with complex scanning to reduce the number of revolutions needed. For LSI process inspection, it uses lower rotation speeds with simple spiral scanning to maintain positional precision. This dynamic adjustment resolves the contradiction between speed and inspection time by optimizing parameters for each specific application.
Solution Approach 2:
The patent changes operational parameters (rotation speed, scan pattern, beam spot size) according to the inspection step requirements. This allows the system to reduce inspection time for total inspection applications while maintaining appropriate quality levels for each inspection purpose, resolving the time-speed tradeoff.
3Measurement precision
If simple spiral scanning is used, then the positional precision of defect coordinates is maintained, but the inspection efficiency decreases and more revolutions per minute are required
Solution Approach 1:
The system dynamically selects the scanning method based on inspection step requirements. For LSI process inspection where positional precision is critical, it uses simple spiral scanning. For final shipment inspection where overall defect detection is sufficient, it uses complex scanning with optical deflector to improve efficiency. This dynamic selection resolves the contradiction by matching the scanning method to the specific inspection objectives.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system significantly reduces inspection time and improves production efficiency by performing defect inspections under tailored conditions, achieving high sensitivity and precision in defect detection.
Implementation Method 1
an optical deflector that scans the laser beam emitted from the laser light source on the workpiece
Implementation Method 2
detect the light beam scattered from the surface, thereby detecting the presence of defects
Data Source
AI summary
A laser scattering defect inspection system includes: a stage unit that rotates a workpiece W and transports the workpiece W in one direction; a laser light source that emits a laser beam LB toward the workpiece W mounted on the stage unit; an optical deflector that scans the laser beam LB emitted from the laser light source on the workpiece W; an optical detector that detects the laser beam LB scattered from the surface of the workpiece W; a storage unit that stores defect inspection conditions for each inspection step of a manufacturing process of the workpiece W, where the conditions include the rotation speed and the moving speed of the workpiece W by the stage unit, the scan width on the workpiece W and the scan frequency by the optical deflector; and a control unit that reads the defect inspection conditions stored for each inspection step in the storage unit and controls the driving of the stage unit and the optical deflector under the conditions.