Defect Inspection Timing Correction for Semiconductor Sensitivity
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Solution Overview
Problem
Conventional defect inspection methods struggle to detect minute defects on semiconductor and thin film substrates with high sensitivity due to the rapid decrease in scattered light intensity as defect sizes approach the detection limit, and existing methods to enhance scattered light often risk damaging the sample by increasing laser power or temperature.
Innovation Solution
A defect inspection method that corrects detection timing errors of scattered light rays from multiple irradiations on the same area, using a reference wafer with known defects to align and add or average the signals, thereby improving sensitivity without sample damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser power is increased to enhance scattered light intensity for detecting minute defects, then defect detection sensitivity is improved, but sample damage risk increases due to temperature rise
Solution Approach 1:
The patent applies periodic action by irradiating the same area multiple times with lower-power laser beams and accumulating the scattered light signals. Instead of using a single high-power irradiation that would cause sample damage, the system performs repeated low-power irradiations and adds the detected signals together, achieving high detection sensitivity without exceeding the sample's thermal tolerance threshold.
2Measurement precision
If multiple scattered light rays from the same area are added to improve detection sensitivity, then signal intensity increases, but detection timing errors cause signal cancellation and reduced sensitivity
Solution Approach 1:
The patent employs feedback by using a reference wafer with known defect positions to detect and measure timing errors in the detection system. The detected timing deviations are then used to correct the detection timing of scattered light signals from actual samples, ensuring that multiple signals from the same defect align properly during accumulation and do not cancel each other out.
3Productivity
If defect size decreases to meet miniaturization requirements, then product integration increases, but scattered light intensity decreases rapidly making detection difficult
Solution Approach 1:
The patent applies merging by combining multiple scattered light signals from repeated irradiations of the same area. Since scattered light intensity decreases rapidly with defect size (I∝d^6), the system compensates for the weak signals from minute defects by accumulating multiple detections, effectively merging the signal strength to achieve detectable levels without requiring higher laser power.
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
This method enhances defect detection sensitivity while preventing sample damage by accurately aligning and combining scattered light signals from multiple irradiations, effectively addressing the challenge of detecting small defects without increasing laser intensity or temperature.
Implementation Method 1
a laser beam focused to a few tens μm is irradiated thereon and scattered light from the defect is converged and detected
Data Source
AI summary
A method for inspecting a defect of a surface of a sample, includes irradiating a laser beam on the sample surface a plurality of times so that at least part of an illumination field of the laser beam on the sample surface illuminates a first area of the sample surface each of the plurality of times, detecting a plurality of scattered light rays from the first area caused by the plurality of times of irradiation, correcting errors of detection timings for the plurality of scattered light rays detected in the detection step, and determining a defect on the sample surface based on the plurality of scattered light rays in accordance with the correcting errors of detection timings.