Evanescent Field Substrate Inspection for Nanometer Defect Detection
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Solution Overview
Problem
Current commercially available apparatuses are unable to detect nanometer-scale defects and variations across an entire substrate surface with sufficient precision and speed, failing to meet the requirements of positional accuracy and measurement time for commercial viability.
Innovation Solution
A method and apparatus that utilize patterned inspection radiation to create an enhanced field, allowing for the detection of variations by receiving scattered radiation and processing changes induced by surface plasmons, with the ability to position the optical element within a distance smaller than the wavelength of the inspection radiation to create an evanescent field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scatterometers with large targets (e.g., 40 μm by 40 μm) are used, then measurement capability is provided, but the space occupied by targets increases and smaller features cannot be inspected
Solution Approach 1:
The patent changes the fundamental measurement parameters by using evanescent fields instead of conventional propagating light fields, enabling detection of nanometer-scale features without requiring large target structures. This parameter change allows the measurement system to resolve much smaller features while occupying minimal substrate area.
Solution Approach 2:
The patent replaces the conventional optical measurement system with an evanescent field-based detection system. By using total internal reflection to generate evanescent fields that penetrate into the substrate, the system achieves higher resolution without mechanical or structural modifications to the substrate targets.
2Measurement precision
If conventional inspection methods are used, then existing technology is maintained, but nanometer-scale defects cannot be detected with sufficient precision and speed
Solution Approach 1:
The patent achieves both high precision and high speed by changing the physical parameters of the inspection radiation. Evanescent fields provide exponential field decay that enhances sensitivity to surface variations at nanometer scales, while the optical nature of the fields enables rapid scanning across the substrate surface.
Solution Approach 2:
The patent employs periodic scanning of the evanescent field across the substrate surface, allowing rapid acquisition of measurement data at multiple positions. This periodic action enables comprehensive coverage of the substrate while maintaining high measurement speed through efficient data collection cycles.
3Measurement precision
If the optical element is positioned close to the substrate to create an evanescent field, then detection precision is improved, but the gap control complexity increases
Solution Approach 1:
The patent implements feedback control mechanisms to maintain the optimal gap between the optical element and substrate. By continuously monitoring the evanescent field interaction and adjusting the gap position, the system maintains high detection precision while automatically compensating for positioning variations.
Solution Approach 2:
The patent designs the system to self-adjust the gap positioning through the physical interaction of the evanescent field with the substrate. The field penetration depth naturally provides feedback on gap distance, allowing the system to self-optimize without complex external control mechanisms.
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 the detection of nanometer-scale defects with improved precision and speed, achieving the necessary positional accuracy and measurement time for commercial viability by enhancing the interaction between the substrate surface and inspection radiation.
Implementation Method 1
detecting any changes to at least one characteristic of the received radiation, the said changes being induced by the generation of a surface plasmon at said surface of the optical element
Implementation Method 2
positioning the surface of the optical element within a distance smaller than a wavelength of the patterned inspection radiation to the surface of the substrate
Implementation Method 3
receiving scattered radiation resultant from interaction between the enhanced field and the substrate surface
Data Source
AI summary
Disclosed is a method and associated inspection apparatus for detecting variations on a surface of a substrate. The method comprises providing patterned inspection radiation to a surface of a substrate. The inspection radiation is patterned such that an amplitude of a corresponding enhanced field is modulated in a manner corresponding to the patterned inspection radiation. The scattered radiation resultant from interaction between the enhanced field and the substrate surface is received and variations on the surface of the substrate are detected based on the interaction between the enhanced field and the substrate surface. Also disclosed is a method of detecting any changes to at least one characteristic of received radiation, the said changes being induced by the generation of a surface plasmon at said surface of the optical element.