Multispectral Wafer Inspection Optical System
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Solution Overview
Problem
Current inspection processes for wafers are inefficient in detecting both large and small defects, as they often require multiple passes with different tools or wavelengths, leading to increased time and cost, especially with the advancement of lithographic deposition technology reducing defect sizes beyond visible wavelength detection capabilities.
Innovation Solution
An optical system incorporating an off-axis reflective focusing system with a beamsplitter to separate visible and ultraviolet wavelengths, allowing for simultaneous detection of large defects in the visible spectrum and small defects in the UV spectrum in a single pass, using a microscope objective and multiple mirrors to project a telecentric image, which is then separated and imaged by detectors for both spectrums.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visible wavelengths are used to detect large defects, then large defects can be detected, but small defects cannot be detected
Solution Approach 1:
The optical system is segmented into multiple independent detection channels, each optimized for specific wavelength ranges. The visible spectrum channel detects large defects while the UV spectrum channel detects small defects, allowing simultaneous multi-scale defect detection without compromising precision or versatility
Solution Approach 2:
The inspection system is designed with multi-functionality to detect defects across different size scales and spectral ranges using a single integrated platform. By incorporating both visible and UV detection channels, the system universally handles both large and small defects that would otherwise require separate inspection processes
2Measurement precision
If multiple passes with different tools are used to detect various defects, then detection completeness is improved, but inspection time and cost increase
Solution Approach 1:
Multiple inspection functions are merged into a single integrated optical system. The visible and UV detection channels, along with multiple field-of-view objectives, are combined to perform what would traditionally require multiple separate passes and tools, thereby maintaining detection completeness while significantly improving inspection efficiency
Solution Approach 2:
The system enables continuous simultaneous detection across multiple spectrums and fields of view in a single inspection pass. Rather than performing sequential inspections with different tools, the system continuously captures defect information across the entire wafer surface in both visible and UV ranges simultaneously, eliminating idle time between inspection passes
3Productivity
If a single optical system is used for both visible and UV detection, then inspection efficiency is improved, but optical system complexity increases
Solution Approach 1:
The optical system is divided into distinct visible and UV detection channels with separate optical paths and detectors. This segmentation allows each channel to be optimized for its specific wavelength range while maintaining a unified system architecture, managing complexity through modular design
Solution Approach 2:
A beamsplitter acts as an intermediary component that separates the incoming light into visible and UV components, directing each to its respective detection channel. This intermediary element enables the system to handle multiple spectrums simultaneously while maintaining manageable optical path complexity
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
Enables efficient detection of both large and small defects in a single inspection pass, reducing time and cost by generating composite images from visible and UV spectrums, thereby improving the efficiency of wafer inspection processes.
Implementation Method 1
a beamsplitter to receive a light from the off-axis reflective focusing system and to separate the light into a first spectrum and a second spectrum
Data Source
AI summary
An optical system and design can image objects under inspection in the ultraviolet (UV) and visible spectrums. This imaging can be used to detect both large defects in the visible spectrum and small defects in the UV spectrum in a single pass while reducing the time and cost of the inspection process. The optical system may include an off-axis reflective focusing system for aberration correction with a beamsplitter to separate the visible spectrum from the UV wavelengths. Cameras may then image visible and UV wavelengths.