Inspection Apparatus Multi-Angle Scattered Light Detection
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Solution Overview
Problem
Conventional inspection methods for semiconductor substrates struggle to accurately detect microscopic defects and contamination due to the isotropic distribution of light scattered from surface roughness, which reduces the effectiveness of additive averaging techniques.
Innovation Solution
An inspection apparatus is designed with multi-azimuth and multi-elevation angle detection optics to selectively use forward, sideward, or backward-scattered light signals, and a signal-processing unit performs arithmetic operations on these signals to improve the signal-to-noise ratio for defect and haze detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additive averaging of signals detected from multiple directions is used, then the signal-to-noise ratio improves for micro-defect detection, but the effectiveness decreases when shot noise from surface roughness is non-uniform across detection directions
Solution Approach 1:
The patent segments the detection process by separating defect detection and haze detection into distinct functional paths. Defect detection uses signals from multiple detection units with different azimuth and elevation angles, while haze detection specifically uses signals from detection units positioned at elevation angles of 45 degrees or more. This segmentation allows each detection type to use optimally selected signals, resolving the contradiction between improving S-N ratio through averaging and maintaining reliability when noise is non-uniform.
Solution Approach 2:
The patent applies local quality by assigning different detection strategies to different spatial regions and signal characteristics. For defect detection, signals from all detection units are processed to maximize S-N ratio. For haze detection, only signals from specific elevation angles (45 degrees or more) are used, as these regions provide better haze discrimination. This localized optimization resolves the contradiction by adapting the detection method to the specific measurement goal.
2Measurement precision
If multi-azimuth and multi-elevation angle detection optics are used to selectively detect scattered light signals, then detection precision for micro-defects and surface roughness improves, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing a single detection optics system that serves multiple purposes: detecting both micro-defects and surface roughness (haze) simultaneously. The same array of detection units with different azimuth and elevation angles is used for both defect detection and haze detection, just with different signal processing strategies. This universal approach improves detection precision for both applications while avoiding the need for separate detection systems, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges defect detection and haze detection functions into a single integrated inspection apparatus. Multiple detection units with different azimuth and elevation angles are combined into one system, and the signal processing unit processes signals from all units to perform both defect detection and haze detection. This merging approach achieves high detection precision for both micro-defects and surface roughness while maintaining a compact, unified device structure rather than requiring separate complex systems.
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 approach enables more accurate detection of micro-defects and surface roughness by isolating and processing specific light scattering patterns, enhancing the signal-to-noise ratio and improving detection precision.
Implementation Method 1
irradiates the surface of a sample with a laser beam condensed to several tens of microns, and acquires/detects the light scattered from defects or contamination
Implementation Method 2
detection optics being adapted to detect the light scattered from the inspection region, in forward direction relative to the direction of the illumination
Data Source
AI summary
An inspection method and apparatus for detecting defects or haze of a sample, includes illuminating light to the sample from an oblique direction relative to a surface of the sample with an illuminator, detecting first scattered light at a forward position relative to an illuminating direction from the sample with a first detector, detecting second scattered light at a sideward or backward position relative to the illuminating direction from the sample with a second detection, and processing a first signal of the first scattered light and a second signal of the second scattered light with different weighting for the first signal and for the second signal with a processor.