Semi-Circular Focusing Lens for Ellipsometer Auto-Focus
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Solution Overview
Problem
Conventional ellipsometers struggle to precisely measure minute patterns in thin films due to the mismatch between the size of the light spot and the pattern, leading to imprecise focusing and measurement.
Innovation Solution
An ellipsometer with an improved auto-focus function, featuring a gantry with arc-shaped guides and coupling portions, a semi-circular or semi-spherical focusing lens positioned on the sample, and a polarization generator and analyzer system that adjusts light paths and polarization, allowing for precise focusing and measurement of thin films regardless of light wavelength or incident angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ellipsometer uses a standard light spot for measurement, then the measurement process is simple, but the light spot cannot be precisely focused on minute patterns, leading to poor measurement precision
Solution Approach 1:
The patent introduces a focusing lens with a semi-circular vertical section (semi-spherical or semi-cylindrical shape) to concentrate the light spot onto minute patterns. This curved optical element transforms the divergent light into a focused beam, enabling precise measurement of sub-10nm patterns while maintaining system simplicity through a single geometric modification rather than complex multi-component assemblies
2Measurement precision
If the light spot size is larger than the pattern size, then the illumination covers the entire pattern, but the measurement precision deteriorates because the light cannot be precisely focused on the minute pattern
Solution Approach 1:
The focusing lens creates a localized high-intensity light region precisely at the pattern location. Instead of uniformly illuminating a large area, the system concentrates optical energy into a small focal region matching the pattern dimensions, achieving both precise spatial targeting and sufficient illumination intensity for accurate measurement
3Measurement precision
If the ellipsometer uses a fixed focus system, then the device structure is simple, but it cannot adapt to different sample positions, reducing measurement accuracy
Solution Approach 1:
The semi-circular focusing lens provides an automatic self-focusing effect through its geometric shape. When light passes through the lens, the curved surface automatically refracts and concentrates the light onto the sample plane without requiring manual adjustment or complex active focusing mechanisms, achieving adaptive focusing through passive geometric design
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 precise measurement of thin films with reduced measurement time by automatically adjusting focus to the sample, ensuring accurate analysis of both single and multi-layered films, even when light spot sizes do not match pattern sizes.
Implementation Method 1
a focusing lens disposed on a sample on a stage
Implementation Method 2
Ellipsometry refers to a method of measuring a complex refractive index of a material based on a wavelength of light by identifying changes in polarization characteristics of light
Data Source
AI summary
An ellipsometer includes: a gantry; a polarization generator and a polarization analyzer mounted in the gantry; and a focusing lens disposed on a sample on a stage, wherein the sample is an object to be measured, wherein a vertical section of the focusing lens is a semi-circle.