Pattern Evaluation Using Optical Filtering for Fine Pitches
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Solution Overview
Problem
Current pattern evaluation methods struggle to accurately assess fine patterns with line widths below 40 nm, as they are beyond the resolution limit of optical systems, leading to reduced throughput and low inspection accuracy, especially in nanoimprint lithography where defects significantly impact yield.
Innovation Solution
A pattern evaluation method and apparatus that uses a light source with a wavelength longer than twice the pattern pitch, acquiring optical images and allocating gradation values to each pixel, converting these values into average line width and roughness information, and creating maps to represent distribution, allowing for high-accuracy evaluation of fine patterns without reducing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light source with wavelength shorter than pattern pitch is used to resolve fine patterns, then measurement precision is improved, but productivity deteriorates due to low throughput
Solution Approach 1:
The patent introduces an optical filter as an intermediary element that selectively transmits light wavelengths. By placing a filter with a specific passband between the light source and the pattern, it enables the use of longer wavelengths (higher throughput) while still achieving the resolution needed for fine patterns (below 40 nm), thus resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The patent changes the wavelength parameter of the light source from traditional short wavelengths (which provide resolution but low throughput) to longer wavelengths combined with optical filtering. This parameter change allows maintaining or improving measurement precision while significantly enhancing productivity by using wavelengths that are easier to generate and detect with higher throughput
2Productivity
If a light source with wavelength longer than twice the pattern pitch is used, then productivity is improved, but measurement precision deteriorates due to insufficient resolution
Solution Approach 1:
The optical filter acts as a mediator that enables the use of longer wavelengths (improving productivity) while maintaining the ability to detect fine patterns (preserving measurement precision). The filter's selective transmission characteristics ensure that only the desired wavelength range passes through, preventing loss of resolution despite using longer wavelengths
Solution Approach 2:
The patent moves the solution from the wavelength dimension alone to a two-dimensional approach combining wavelength selection with optical filtering. By adding the filtering dimension, it becomes possible to use longer wavelengths (productivity improvement) while maintaining the effective resolution needed for fine pattern detection (measurement precision preservation)
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 high-accuracy evaluation of fine patterns with line widths below 40 nm, improving defect detection and reducing variations in pattern formation, thereby enhancing the yield and productivity in semiconductor manufacturing.
Implementation Method 1
illuminating light from a light source constituting an optical system and acquiring an optical image of a sample
Data Source
AI summary
A pattern evaluation method comprising the steps of, illuminating light from a light source constituting an optical system and acquiring an optical image of a sample having a repeated pattern with a period not more than a resolution of the optical system, allocating a gradation value to each pixel of the optical image and obtaining at least one of an average gradation value for each predetermined unit region and deviation of the gradation value in the unit region, and performing at least one of a process of converting the average gradation value into average line width information in the region of the repeated pattern and a process of converting the deviation of the gradation value into roughness of the repeated pattern and creating a map representing distribution of at least one of the average line width information and the roughness with the use of an obtained converted value.