Micro-lens Array Homogenizer for Wafer Inspection Illumination
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Solution Overview
Problem
Existing wafer inspection technologies face challenges in achieving high-intensity, homogeneous illumination, which is crucial for accurate defect detection as inhomogeneous illumination can falsely indicate defects during image comparison.
Innovation Solution
The apparatus employs a combination of collector optics, homogenizing optics with two micro-lens arrays, and Fourier optics to project a light source onto a specular surface, ensuring uniform and high-intensity illumination by overlapping near-field light distributions, and an objective optics to project the surface onto a detector for image recording.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional illumination systems are used, then the structure is simple, but the illumination intensity is insufficient and homogeneity is poor
Solution Approach 1:
The illumination system is segmented into multiple functional modules: collector optics for light gathering, homogenizing optics with micro-lens arrays for uniformity, and Fourier optics for intensity distribution control. This segmentation allows each module to optimize specific parameters without compromising overall system performance.
Solution Approach 2:
The optical components are arranged in a nested configuration where the micro-lens arrays are positioned within the focal regions of previous optical elements. The first micro-lens array is nested within the collector optics focal region, and the second micro-lens array is nested within the first array's focal region, creating a compact nested structure that maximizes space utilization and optical efficiency.
2Illumination intensity
If conventional illumination systems are used, then the device complexity is low, but the illumination homogeneity is insufficient
Solution Approach 1:
The micro-lens arrays provide local quality enhancement by independently controlling light distribution in different spatial regions. Each micro-lens acts as a local light redistribution element, ensuring uniform illumination across the entire wafer surface while maintaining the ability to address local variations in light intensity.
Solution Approach 2:
The system changes optical parameters through the use of micro-lens arrays with specific focal lengths and spacing configurations. By adjusting the focal lengths of the micro-lenses and their relative positions, the illumination homogeneity and intensity distribution can be precisely controlled to match the requirements of different inspection applications.
3Productivity
If high-intensity illumination is used, then throughput increases, but false defect indications occur due to inhomogeneity
Solution Approach 1:
The homogenizing optics with micro-lens arrays serve as an intermediary between the light source and the wafer surface. This intermediary component transforms the non-uniform high-intensity light from the collector optics into a homogeneous illumination pattern, enabling both high throughput and accurate defect detection without false indications.
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 configuration achieves an extremely uniform and high-intensity illumination on the wafer, enhancing inspection throughput and accuracy by minimizing false defect indications.
Implementation Method 1
the near-field distribution of the light source is homogenized by overlapping the images
Implementation Method 2
the collector optics and the first micro-lens array project the light source onto the second micro-lens array
Implementation Method 3
a Fourier optics for transmitting the light from the homogenizing optics onto the specular surface
Data Source
AI summary
The present invention relates to an apparatus for illuminating and inspecting a specular surface, comprising a light source, a collector optics for collecting the light from the light source, a homogenizing optics for transmitting the light from the collector optics having a first micro-lens array downstream of the collector optics, and a second micro-lens array downstream of the first micro-lens array, a Fourier optics for transmitting the light from the homogenizing optics onto the specular surface, an objective optics, and a detector for receiving an image, wherein the collector optics and the first micro-lens array project the light source onto the second micro-lens array and wherein the second micro-lens array and the Fourier optics project the first micro-lens array onto the specular surface, and wherein the objective optics projects the specular surface onto the detector.