Multi-Anode Detector Optical Axis Alignment for Wafer Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor wafer inspection systems using a rotating wafer and an elliptical light beam, the alignment of the optical axis between the optical image detection unit and the scattered light detection unit is not guaranteed, leading to inaccurate defect detection.
Innovation Solution
A multi-anode detection system is used to detect scattered light, with an adjustment unit aligning the optical axis of the elliptical beam and a correction unit improving detection accuracy by rotating or amplitude correcting the light beam, ensuring the light receiving axis of the multi-anode detector is aligned with the elliptical beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an optical image detection unit is disposed separately from a scattered light detection unit, then the optical axis can be adjusted in the optical image detection unit, but the optical axis is not necessarily in alignment in the scattered light detection unit and the accuracy of the position of the defect detection is not improved
Solution Approach 1:
The patent combines the optical image detection unit and the scattered light detection unit into a single integrated detection unit. This integration ensures that the optical axis alignment is consistent across both detection functions, as they now share the same detection pathway and calibration reference, thereby resolving the misalignment issue while maintaining ease of operation
Solution Approach 2:
The detection unit is designed to perform multiple functions: both optical image detection and scattered light detection. By making the detection unit universal, it eliminates the need for separate alignment procedures for different detection modes, ensuring consistent optical axis alignment across all detection functions
2Measurement precision
If a multi-anode detector is used instead of a photomultiplier, then scattered light detection capability is improved, but it becomes necessary to calibrate the optics system with high accuracy such that it is necessary to align the optical axis of the elliptical beam with the multi-anode direction
Solution Approach 1:
The patent merges the optical image detection function and scattered light detection function into a single integrated detection unit that uses the multi-anode detector. This integration allows the system to leverage the high detection capability of the multi-anode detector while using the same detection pathway for both functions, thereby reducing the overall calibration complexity despite the higher precision requirements
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 enhances the accuracy of defect detection on semiconductor wafers by ensuring precise alignment and correction of the light beam, leading to improved position and size measurement of defects.
Implementation Method 1
detecting a defect on the wafer such as a foreign object by utilizing scattered light reflected on the wafer
Data Source
AI summary
Provided is a method wherein a multi-anode detector is used for the purpose of detecting scattered light from a wafer, data obtained from the detector (multi-anode) for detecting defects is used, the shape of a beam radiated to the wafer, a rotational shift between the radius direction and the beam long side, and the like are calculated, and the optical axis of the irradiation beam is adjusted. Furthermore, the method is provided with a technique which feeds back the correction quantities for rotation and amplitude to inspection signal data, on the basis of the correction data, and corrects inspection data. Since fine correction with the adjustment of an optics system and signal processing is made possible, positional accuracy of defect inspection and accuracy of defect level (defect size) are improved.