Defect Inspection Using Polarized Light Beams
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current defect inspecting apparatuses using optical microscopes face challenges in achieving high resolution and sensitivity due to difficulties in illuminating fine structural objects with uniform, high-intensity short-wavelength light, leading to low brightness and high costs, especially with the miniaturization of reticle, photo-mask, LSI, and MEMS patterns.
Innovation Solution
The method involves using multiple polarized light beams with different properties to illuminate and scan the object's surface, splitting the light into p-polarized and s-polarized beams, and detecting the reflected or scattered light to generate high-resolution images, allowing for nonsimultaneous double-scanning and improving resolving power and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If short-wavelength light is used to improve resolving power, then the ability to resolve fine surface structures is improved, but the illumination intensity becomes insufficient and the system cost increases
Solution Approach 1:
The patent combines multiple light beams with different polarization states (p-polarized and s-polarized light) to illuminate the inspection area simultaneously. This merging of multiple light sources increases the total illumination intensity while maintaining the short wavelength needed for high resolving power, thereby resolving the contradiction between improved measurement precision and insufficient illumination intensity.
2Measurement precision
If high NA objective lens is used to improve resolving power, then the ability to resolve fine patterns is improved, but the system cost and complexity increase significantly
Solution Approach 1:
The patent changes the illumination parameters by using multiple polarized light beams instead of conventional single-source illumination. This parameter change allows the system to achieve high resolving power without requiring extremely high NA objective lenses, thereby reducing system complexity and cost while maintaining measurement precision.
3Device complexity
If conventional single light source illumination is used, then the system is simple, but the brightness is insufficient and exposure time must be very long
Solution Approach 1:
The patent merges multiple light beams with different polarization states to illuminate the inspection area simultaneously, significantly increasing the total brightness. This approach maintains relative system simplicity while solving the insufficient brightness problem, thereby reducing the required exposure time without dramatically increasing device 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
This approach enables high-resolution and high-sensitivity defect inspection with reduced costs by enhancing the optical resolving power and throughput, effectively addressing the limitations of existing systems in handling miniaturized patterns.
Implementation Method 1
a light beam from a light source is split into N (N is natural number equal to or more than two) polarized light beams, each of which has different property
Implementation Method 2
outputting the each of N polarized light beams reflected by the surface, the each of N polarized light beams passed-through the object or the each of N polarized light beams scattered by the surface, as an image signal
Implementation Method 3
outputting the each of N polarized light beams reflected by the surface, the each of N polarized light beams passed-through the object or the each of N polarized light beams scattered by the surface, as an image signal
Data Source
AI summary
A method for forming an image of an object includes: illuminating sequentially a surface of the object arranged in the same shooting area using each of N (N is natural number equal to or more than two) polarized light beams, each of which has different property; scanning the surface using the each of N polarized light beams; and outputting the each of N polarized light beams reflected by the surface, the each of N polarized light beams passed-through the object or the each of N polarized light beams scattered by the surface, as an image signal.