Coherent Diffraction Imaging for Semiconductor Defect Detection
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Solution Overview
Problem
Current defect detection methods in lithographic processes, particularly for modern semiconductor structures, face challenges due to the small dimensions of features which cannot be imaged using optical metrology techniques, and scanning electron microscopy is time-consuming.
Innovation Solution
An inspection apparatus and method utilizing coherent diffraction imaging (CDI) with a radiation source and image detector, combined with an illumination optical system, to capture diffraction patterns and calculate synthetic images for defect identification, avoiding the need for physical lenses and enabling high-resolution defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscopy is used to resolve modern product structures, then measurement precision is improved, but productivity deteriorates due to time-consuming inspection
Solution Approach 1:
The patent replaces the mechanical scanning electron microscopy system with an optical metrology system using coherent diffraction imaging. This substitution enables imaging of modern product structures at visible wavelengths while maintaining high throughput speeds, thus improving productivity without sacrificing measurement precision.
2Productivity
If optical metrology techniques at visible wavelengths are used, then productivity is improved, but measurement precision deteriorates because small features cannot be imaged
Solution Approach 1:
The patent changes the wavelength parameter of the radiation used in optical metrology from visible wavelengths to extreme ultraviolet wavelengths. This parameter change enables the optical system to resolve much smaller features while maintaining the high productivity advantages of optical metrology over electron microscopy.
3Productivity
If conventional optical metrology is used for defect detection, then productivity is maintained, but measurement precision deteriorates for periodic structures
Solution Approach 1:
The patent segments the inspection process into multiple measurements taken at different positions across the periodic structure. By combining these segmented measurements through coherent diffraction imaging, the system achieves high measurement precision for periodic structures while maintaining productivity through efficient data processing.
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 and high-resolution defect detection in both periodic and non-periodic structures, improving the accuracy and speed of defect identification in semiconductor manufacturing, thereby enhancing the control of lithographic processes.
Implementation Method 1
capturing at least one diffraction pattern formed by the radiation after scattering by the product structure
Implementation Method 2
capturing at least one diffraction pattern formed by the radiation after scattering by the product structure
Data Source
AI summary
A product structure (407, 330′) is formed with defects (360-366). A spot (S) of EUV radiation which is at least partially coherent is provided on the product structure (604) to capture at least one diffraction pattern (606) formed by the radiation after scattering by the product structure. Reference data (612) describes a nominal product structure. At least one synthetic image (616) of the product structure is calculated from the captured image data. Data from the synthetic image is compared with the reference data to identify defects (660-666) in the product structure. In one embodiment, a plurality of diffraction patterns are obtained using a series overlapping spots (S(1)-S(N)), and the synthetic image is calculated using the diffraction patterns and knowledge of the relative displacement. The EUV radiation may have wavelengths in the range 5 to 50 nm, close to dimensions of the structures of interest.