Acousto-Optic Deflector Multi-Perspective Wafer Scanning
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Solution Overview
Problem
Current wafer analysis tools face challenges in distinguishing defects from wafer noise due to diffuse reflection from surface irregularities, which limits defect detection accuracy.
Innovation Solution
A computerized system utilizing an acousto-optic deflector to obtain multi-perspective scan data by scanning consecutive lines from different perspectives, with overlapping coverage to enhance defect detection by integrating cross-perspective covariances and noise analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-perspective scanning is used, then scanning speed is maintained, but defect detection precision deteriorates due to inability to distinguish defects from wafer noise
Solution Approach 1:
The scanning process is segmented into multiple perspectives, where the wafer is scanned from different angular positions (e.g., 0 degrees, 45 degrees, 90 degrees, 135 degrees). Each perspective provides independent measurement data, and the segmentation allows defects to be distinguished from wafer noise through comparative analysis across segments.
Solution Approach 2:
The scanning system transitions from single-dimension (single perspective) to multi-dimension (multiple perspectives) by introducing angular variation. This dimensional expansion enables the system to capture defect characteristics from different orientations, improving discrimination between real defects and noise artifacts.
2Measurement precision
If multi-perspective scanning is implemented, then defect detection precision improves, but scanning time increases
Solution Approach 1:
The multi-perspective scanning is implemented as a continuous process where the wafer stage moves steadily while the illumination and collection systems rotate to different angular positions. This continuous scanning approach eliminates the need for repeated scans at each perspective, maintaining constant measurement action across all perspectives without interrupting the overall scanning flow.
Solution Approach 2:
The system employs periodic rotation of the illumination and collection systems to different angular perspectives during continuous wafer scanning. This periodic action allows multiple perspectives to be acquired in a single pass, with each perspective captured at regular intervals during the continuous scan, thereby reducing total scanning time compared to sequential multi-pass approaches.
3Adaptability or versatility
If conventional single-perspective scanning is used, then system complexity is low, but ability to distinguish defects from noise deteriorates
Solution Approach 1:
The scanning system is designed with multi-functional capabilities, where a single scanning apparatus can operate in both single-perspective mode (for routine scanning) and multi-perspective mode (for enhanced defect discrimination). The illumination and collection systems can rotate to multiple angular positions, allowing the same hardware to adapt to different detection requirements without requiring separate specialized systems.
Solution Approach 2:
The system incorporates dynamic elements including rotatable illumination sources and collection systems that can adjust their angular positions during scanning. This dynamic capability allows the system to transition between different perspectives on-the-fly, providing adaptability for defect discrimination while maintaining a relatively simple base configuration that can operate in static single-perspective mode when needed.
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
Improves defect detection rates by distinguishing defects from wafer noise through simultaneous multi-perspective scanning and integrated analysis, leading to more accurate identification of defects on wafers.
Implementation Method 1
An acousto-optic deflector (AOD) configured to focus the at least one light beam such as to generate a beam train scanned along consecutive lines on the slice
Data Source
AI summary
Disclosed herein is a computerized system including scanning equipment configured to obtain multi-perspective scan data of a slice on a sample. The scanning equipment includes: (i) a light source configured to generate a light beam; (ii) an acousto-optic deflector (AOD) configured to focus the light beam such as to generate a beam train scanned along consecutive lines on the slice, in groups of n≥2 successively scanned lines, along each of which the beam train forms at least one illumination spot, respectively; and (iii) one or more detectors configured to sense light returned from the slice. The n≥2 lines are scanned different perspectives, respectively. The consecutive lines may be longitudinally displaced relative to one another, such as to overlap in 100·(n−1)/n % of widths thereof, so that the slice may be fully scanned in each of the perspectives.