Periodic Optical Test Structure for Inline Meta-Lens Measurement
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Solution Overview
Problem
Current inline inspection processes for meta-optical devices, such as scanning electron microscopes, struggle to accurately measure the critical dimensions of meta-lens structures due to their complex, non-periodic arrangement of pillars, leading to unpredictable device performance and reduced production quality.
Innovation Solution
An optical test structure is developed with a specific arrangement of optical units on a substrate, allowing for inline optical measurement to predict device performance by correlating light beam intensity with critical dimension differences, thereby improving measurement accuracy and reflecting manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscopes are used for inline inspection of meta-lens structures, then device performance prediction is attempted, but measurement accuracy deteriorates due to charging effects and complex non-periodic pillar arrangements
Solution Approach 1:
The patent replaces the mechanical/electronic scanning electron microscope system with an optical measurement system. The optical test structure uses periodic pillar arrangements that interact with light through diffraction and interference effects, enabling critical dimension measurements without charging effects. Light beams are emitted through the test structure, and diffraction patterns are analyzed to determine critical dimensions, substituting the problematic electron beam mechanism with an optical field-based approach.
2Measurement precision
If scanning electron microscopes are used for inline inspection, then device performance prediction is attempted, but inspection efficiency deteriorates due to complex measurement procedures
Solution Approach 1:
The patent creates an optical test structure that copies the essential geometric features (critical dimensions) of the actual meta-lens structure but uses simplified periodic arrangements. This optical copy structure allows for rapid optical measurement that reflects the critical dimensions of the original structure without requiring complex electron microscope procedures. The test structure serves as an optical replica that preserves the measurement-relevant geometry while enabling efficient inspection.
Solution Approach 2:
The optical test structure employs periodic arrangements of optical elements (pillars) rather than the complex non-periodic arrangements of the actual meta-lens. This periodicity creates regular diffraction patterns that are easier to analyze and measure. The periodic structure allows for standardized measurement procedures and simplifies the relationship between measured diffraction patterns and critical dimensions, thereby improving inspection efficiency while maintaining measurement accuracy.
3Adaptability or versatility
If complex non-periodic pillar arrangements are used in meta-lens structures, then optical functionality is achieved, but measurement and inspection difficulty increases
Solution Approach 1:
The patent segments the measurement task into two parts: (1) the actual meta-lens structure with complex non-periodic pillars that performs the optical function, and (2) a separate optical test structure with periodic pillars that performs the measurement function. The test structure is segmented to have regular, periodic arrangements that are easy to measure, while the actual device maintains its complex functionality. This segmentation allows the measurement system to use simplified periodic patterns to infer critical dimensions of the complex structure.
Solution Approach 2:
The optical test structure acts as an intermediary between the measurement system and the actual meta-lens structure. Instead of directly measuring the complex non-periodic pillars of the meta-lens, the system uses the periodic optical test structure as a mediator. The test structure's regular pattern serves as an intermediate reference that can be easily measured optically, and the measured critical dimensions are then correlated back to the actual device structure, facilitating indirect but accurate measurement.
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
The optical test structure enables precise prediction of device performance, reducing inspection time, enhancing productivity, and lowering production costs by accurately measuring critical dimensions without being affected by charging effects.
Implementation Method 1
Meta-optics is an optical technique using meta-surfaces or meta-structures to manipulate characteristics of light (for example, phase, amplitude, or polarization of the light) when the light passes through the meta-surfaces or the meta-structures.
Implementation Method 2
A meta-optical device is generally composed of a planar light-transmissive substrate and millions of dielectric subwavelength nanostructures arranged in an array on the planar light-transmissive substrate
Data Source
AI summary
An optical test structure includes a substrate and at least one optical unit. The at least one optical unit is disposed on the substrate, and includes a first optical element, a second optical element, a third optical element, and a fourth optical element which are spaced apart from each other. The second optical element is disposed between the first optical element and the third optical element. The third optical element is disposed between the second optical element and the fourth optical element. A size of the third optical element is larger than a size of each of the first optical element, the second optical element, and the fourth optical element. The size of each of the second optical element and the fourth optical element is larger than the size of the first optical element.